Sweet Pea Trial 2016

Though I didn’t find 2016 to be a particularly successful year for growing Sweet Peas – the plants grown for my 2016 Sweet Pea Trial didn’t produce as many flowers as I had hoped, my love of Sweet Peas has not diminished in strength.  I love Sweet Peas.  I highly recommend that you experience growing these magnificent annual flowers.

The Sweet Peas I have grown for the 2016 Sweet Pea Trial, are also known by their botanical name of Lathyrus odoratus.  Lathyrus odoratus are a delightfully pretty annual climber, that’s available in a vast range of colours.  I favour the scented Sweet Pea varieties, these fragrant flowers exude a sublime, sweet and alluring floral perfume, that is delicate, fresh and exquisite.

Sweet Peas are very accommodating, here in the UK, you can sow Lathyrus odoratus seeds from September right through until April.  So there’s absolutely no reason not to try growing this pretty annual, you have plenty of opportunity to sow the seeds!

Eight months is of course plenty of time to sow your Sweet Pea seeds, or even to buy plants from your local nursery if you prefer, but if you’re looking to sow Sweet Pea seeds, and have ever wondered what difference the month you choose to sow your seeds in will make, or if you’ve wondered if there’s a perfect time to sow your Sweet Pea seeds, I hope that this article with the results of my 2016 Sweet Pea Trial, will help you.

Sweet Pea Seed Varieties

I selected the following Spencer type Sweet Pea varieties for my 2016 Sweet Pea Trial:

  • Lathyrus odoratus ‘Aphrodite’
  • Lathyrus odoratus ‘Ida King’
  • Lathyrus odoratus ‘John Gray’
  • Lathyrus odoratus ‘Lady Nicholson’
  • Lathyrus odoratus ‘Misty’
  • Lathyrus odoratus ‘Naomi Nazareth’
  • Lathyrus odoratus ‘Pip’s Cornish Cream’
  • Lathyrus odoratus ‘Windsor’

I purchased all of the seeds for my 2016 Sweet Pea Trial from Roger Parsons Sweet Peas.  You can see photographs of all the Spencer type Sweet Pea varieties that featured in my 2016 Sweet Pea Trial below:

Lathyrus odoratus 'Aphrodite' is a vigorous sweet pea that produces white flowers.
Lathyrus odoratus ‘Aphrodite’ is a vigorous sweet pea that produces white flowers.
Lathyrus odoratus 'Ida King' produces pretty lavender coloured flowers.
Lathyrus odoratus ‘Ida King’ produces pretty lavender coloured flowers.
Lathyrus odoratus 'John Gray' produces beautiful flowers that are pale pink on a white ground.
Lathyrus odoratus ‘John Gray’ produces beautiful flowers that are pale pink on a white ground.
The attractive flowers of Lathyrus odoratus 'Lady Nicholson' feature a mauve stripe on a white ground.
The attractive flowers of Lathyrus odoratus ‘Lady Nicholson’ feature a mauve stripe on a white ground.
Lathyrus odoratus 'Misty' produces pretty pale mauve flushed flowers on a white ground.
Lathyrus odoratus ‘Misty’ produces pretty pale mauve flushed flowers on a white ground.
Lathyrus odoratus 'Naomi Nazareth' is a very pretty, pale blue sweet pea.
Lathyrus odoratus ‘Naomi Nazareth’ is a very pretty, pale blue sweet pea.
Lathyrus odoratus 'Pip's Cornish Cream' produces beautiful cream coloured blooms.
Lathyrus odoratus ‘Pip’s Cornish Cream’ produces beautiful cream coloured blooms.
Lathyrus odoratus 'Windsor' is a dark maroon coloured sweet pea.
Lathyrus odoratus ‘Windsor’ is a dark maroon coloured sweet pea.

Sweet Pea Seed Sowing Dates

For my 2016 Sweet Pea Trial, I decided to sow the same varieties of Sweet Pea seeds at each sowing, all the seeds were purchased from the same seed company – Roger Parsons Sweet Peas.  The Sweet Pea seeds were sown in the same growing media, using the same type of seed trays at each sowing.  The seeds for my 2016 Sweet Pea Trial were sown at various times, which I have detailed below.  I selected the seed sowing dates for the 2016 Sweet Pea Trial after evaluating data from my 2015 Sweet Pea Trial, and other Sweet Pea Trials I have previously undertaken.

The first seed sowing for the 2016 Sweet Pea Trial took place on the 10th October 2015, and the last seeds were sown on the 12th March 2016.  These staggered sowings allowed me to compare the number of flowers, the length of the flower stem produced by each sowing, and evaluate if there was a better time of year to sow Sweet Peas.  I also trialled two different methods of growing Sweet Peas, to see if there is a better growing method to train the plants, to produce a greater harvest of flowers, a better quality of flower, or a longer length of stem.

For the 2016 Sweet Pea Trial, seeds were sown on each of the following dates:

  • 10th October 2015
  • 26th October 2015
  • 2nd January 2016
  • 13th February 2016
  • 12th March 2016

Sowing Sweet Pea Seeds

Peat free Compost

All of the Sweet Pea seeds and plants for my 2016 Sweet Pea Trial were grown in the same peat free composts.  All of the composts I chose to use for my 2016 Sweet Pea Trial were produced by Dalefoot Composts.  I chose to use Dalefoot Composts after seeing how well their composts performed in my Peat Free Compost Trials over the past few years.  Dalefoot Composts use natural ingredients, such as bracken and sheep’s wool to create a nutrient rich compost with an increased water holding capacity. 

I sowed all of my Sweet Pea seeds for the 2016 Sweet Pea Trial in Dalefoot Composts Wool Compost, a peat free potting compost, made from natural ingredients including bracken and sheep’s wool, which supply a slow release fertiliser to the seedlings.

I sowed all of the Sweet Pea seeds for my 2016 Sweet Pea Trial in Dalefoot Composts Wool Potting Compost. This peat free compost is made from a blend of compost that includes sheep's wool and bracken in the ingredients. Dalefoot Composts Wool Compost is naturally water retentive, meaning that your seedlings don't require watering as frequently.
I sowed all of the Sweet Pea seeds for my 2016 Sweet Pea Trial in Dalefoot Composts Wool Potting Compost. This peat free compost is made from a blend of compost that includes sheep’s wool and bracken in the ingredients. Dalefoot Composts Wool Compost is naturally water retentive, meaning that your seedlings don’t require watering as frequently.

The inclusion of wool in Dalefoot Composts Wool Compost naturally increases the water holding capacity of this compost.  Consequently, Dalefoot Composts Wool Compost is an ideal choice for sowing the Sweet Pea seeds and growing the seedlings on, as during this early period of the trial, I relied heavily on rainfall to water the seedlings, prior to the plants being planted out in the trials area, which benefits from an automatic watering system.

Although the young Sweet Pea plants inevitably endured periods of drought and stress during the early stages of the 2016 Sweet Pea Trial, these stresses were minimised somewhat due to the water holding capacity of the compost used.  The only negative of using Dalefoot Composts Wool Compost is that during periods of very inclement weather, the potential for damping off, or rotting of the seeds and seedlings is increased, due to the water holding capacity of the compost, combined with prolonged rainfall and wet conditions.  This negative could have been reduced, had a shelter been erected to protect the seedlings during inclement weather, and then removed once the weather brightened.  Naturally, the problems caused by drought, could be erased by regular watering during periods of dry conditions.

I enriched the soil in the trials area, where the Sweet Pea plants were grown, with Dalefoot Composts Wool Compost Double Strength prior to planting.  This Double Strength, peat free compost contains a potent, powerful blend of nutrients that enrich the soil or compost it is added to.  Dalefoot Composts Wool Double Strength Compost is very highly concentrated, a little goes a long way.  This compost can be mixed with spent compost to improve the fertility of the growing media, to enable the growing of plants, or it can be used to enrich poor soil in beds and borders.  Dalefoot Wool Double Strength Compost is a very economical compost to use, I have grown successful, healthy crops by mixing Dalefoot Wool Double Strength concentrated compost with a spent compost that was unable to sustain plant growth when used alone.

The inclusion of wool as an ingredient in this compost, helps to improve the water retaining quality of the compost and the soil it’s added to.  This is especially beneficial to light, free draining, sandy soils, as nutrients and water are quickly washed through these soils.  As sandy soils are free draining, organic matter and nutrients need to be regularly applied, it is best to apply Dalefoot Composts Double Strength Wool Compost in the spring, to minimise the loss of nutrients, and ensure that the Sweet Pea plants can benefit from the addition of this wonderful nutrient rich compost.

Prior to planting out the Sweet Pea plants in the trials ground, for my 2016 Sweet Pea Trial, I used Dalefoot Composts Double Strength Wool Compost to enrich the soil in the trials area.
Prior to planting out the Sweet Pea plants in the trials ground, for my 2016 Sweet Pea Trial, I used Dalefoot Composts Double Strength Wool Compost to enrich the soil in the trials area.

Rootrainers

All of the Sweet Pea seeds for my 2016 Sweet Pea Trial were sown in Deep Rootrainers, which are available online from Haxnicks.  Rootrainers are specially designed seed trays, they’re available in various sizes, and are ideal for sowing seeds, or taking cuttings.  I chose to use Deep Rootrainers to sow my Sweet Pea seeds, as the extra depth that these Rootrainers provide is ideal for growing Sweet Peas, which are naturally deep rooted plants.

Rootrainers are specially designed to maximise your plant’s potential for healthy root growth.  Rootrainers feature individual growing cells, which are ribbed to encourage the roots of the Sweet Pea plants to grow down towards the drainage hole, where they are air pruned.  This air pruning encourages the plant to develop a healthy root system.

As the Lathrus odoratus roots reach the bottom of the Deep Rootrainers they are air pruned. This air pruning encourages further branching of the plants' roots.
As the Lathrus odoratus roots reach the bottom of the Deep Rootrainers they are air pruned. This air pruning encourages further branching of the plants’ roots.

Rootrainers offer many advantages to the gardener, these seed trays open up like a book, allowing you to check on how your plants and their roots are growing, at any time you wish.  Sweet Pea plants grown in Rootrainers are never pot bound, the plants are easily removed from the seed trays, and establish readily when planted.

The ridged Rootrainers cells direct the plants' roots to grow vertically towards the drainage hole. Rootrainers are easy to assemble, they open out like a book, allowing you to monitor how your plants' roots are growing and developing whenever you choose. I grew all of the Sweet Pea plants for my 2016 Sweet Pea Trial in Deep Rootrainers.
The ridged Rootrainers cells direct the plants’ roots to grow vertically towards the drainage hole. Rootrainers are easy to assemble, they open out like a book, allowing you to monitor how your plants’ roots are growing and developing whenever you choose. I grew all of the Sweet Pea plants for my 2016 Sweet Pea Trial in Deep Rootrainers.
A closer look at the Lathyrus odoratus roots developing inside the Deep Rootrainers.
A closer look at the Lathyrus odoratus roots developing inside the Deep Rootrainers.
The Lathyrus odoratus roots in this Deep Rootrainers cell have formed a heart shape!
The Lathyrus odoratus roots in this Deep Rootrainers cell have formed a heart shape!

Rootrainers Racking Station

During the earlier stages of the 2016 Sweet Pea Trial, the seedlings were dependent on rainfall for watering. I grew all of the Sweet Pea plants for my 2016 Sweet Pea Trial in Deep Rootrainers. I used a Rootrainers Racking Station to conveniently store my Rootrainers.
During the earlier stages of the 2016 Sweet Pea Trial, the seedlings were dependent on rainfall for watering. I grew all of the Sweet Pea plants for my 2016 Sweet Pea Trial in Deep Rootrainers. I used a Rootrainers Racking Station to conveniently store my Rootrainers.

I used the Rootrainers Racking Station to lift my packs of Rootrainers off the ground and store them conveniently together outdoors.  Using the Rootrainers Racking Station raises the seedlings up, which makes it easier to tend the plants, it also moves the seedlings out of such easy reach of pests like slugs and snails.  By storing the Deep Rootrainers packs in the Rootrainers Racking Station, the seedlings are held above the ground, so the air is able to circulate freely around the seedlings’ roots, this encourages the air pruning of the Sweet Pea plants’ roots, that all plants grown in Rootrainers benefit from.

The Rootrainers Racking Station raises the Sweet Pea plants up, which makes them easier to tend.
The Rootrainers Racking Station raises the Sweet Pea plants up, which makes them easier to tend.

Irrigation

All of the Sweet Pea seeds and seedlings for my 2016 Sweet Pea Trial were sown and grown outdoors without any protection from inclement weather.  I sowed all of the Sweet Pea seeds for my 2016 Sweet Pea Trial in Deep Rootrainers, which were placed in a Rootrainers Racking Station outdoors, without any protection from the elements.  The Sweet Pea seedlings grown for my 2016 Sweet Pea Trial relied on rainfall, and the water retentive qualities of the Dalefoot Wool Potting Compost that I used for this trial, to hydrate them.

Naturally, the seedlings often endured periods of drought, or periods of very wet weather, neither of which would have been beneficial to the Sweet Pea plants.  The seedlings once sown, experienced the same conditions, although the earlier sown seedlings naturally experienced differing weather conditions than the later sown seedlings, which had not been sown as early.

An automated irrigation system ensured that all of the Sweet Pea plants, both the cordon grown Sweet Pea plants, and the naturally grown Sweet Pea plants, planted with home-made wigwams, once they were planted in the trials area, received the same quantity of water, at the same time, at regular intervals.  During this stage of the 2016 Sweet Pea Trial, the Sweet Pea plants didn’t experience any periods of drought.

Fertilisers

All of the Sweet Pea plants grown for the 2016 Sweet Pea Trial received the same fertilisers, applied at the same rate, at the same time.  As I used nutrient rich composts for the 2016 Sweet Pea Trial, I didn’t need to apply fertilisers very often.

Sweet Pea Seedling Survival Rates

This table shows the number of seedlings that survived to be planted out, for each sowing period and planting type. Eight seeds were planted of each variety at each sowing stage. You can see from the averages/totals, that Lathyrus odoratus 'Ida King' had very low germination and survival rates relative to other varieties. Similarly, the 10th October and 12th March sowings were very unsuccessful - fewer than half the seedlings made it into the ground. Thankfully, we can normalise for these discrepancies by calculating the flowering rate per plant, and extrapolating the data for flowers picked on the plants which did survive.
This table shows the number of seedlings that survived to be planted out, for each sowing period and planting type. Eight seeds were planted of each variety at each sowing stage. You can see from the averages/totals, that Lathyrus odoratus ‘Ida King’ had very low germination and survival rates relative to other varieties. Similarly, the 10th October and 12th March sowings were very unsuccessful – fewer than half the seedlings made it into the ground. Thankfully, we can normalise for these discrepancies by calculating the flowering rate per plant, and extrapolating the data for flowers picked on the plants which did survive.

Sweet Pea Trial Growing Methods

For the 2016 Sweet Pea Trial, as well as trialling different sowing times, to look at how the sowing timing affected flower production, I also trialled two different growing methods, to see how each growing method affected the Sweet Pea plants, and the flowers they produced.  I divided the seedlings from each sowing as equally as was possible, so that some plants from each sowing were grown as cordons, and others as wigwams.

All of the Sweet Pea plants for the 2016 Sweet Pea Trial, whether they were to be grown as cordons, or grown naturally as wigwams, were planted out into the trials area at the same time.  The plants grown for both growing methods were grown, and then planted, in the same composts, and all of the plants received the same level of irrigation.  The only difference these plants experienced was their growing methods.

Pinching out Sweet Peas

Pinching out is the removal of the top growth of the Sweet Pea seedlings.  Pinching out is carried out to encourage branching.  For my 2016 Sweet Pea trial I did not pinch out any of my Sweet Pea plants, no top growth was removed from any of the plants.  The Sweet Pea plants have a naturally branching habit, and so pinching out was not necessary.

Sweet Pea Wigwams

The Sweet Pea plants in this section of the trial were all planted out at the same time, and at the same time as the cordon grown plants.  The wigwam grown Sweet Pea plants were grown in a rather wild, natural way – none of the Sweet Pea plants had any of their tendrils or side shoots removed, and none of the plants were tied to their supports, they were left to grow naturally.

Sweet Pea wigwams.
Sweet Pea wigwams.

The wigwam grown plants were planted more closely together than the cordon grown plants.  These naturally grown Sweet Pea plants were grown up a series of home-made wigwams.  I did not remove any of the Sweet Pea plants’ tendrils or side shoots, the plants required no further tying in or support, as all of the Sweet Pea varieties grown for the 2016 Sweet Pea Trial were self supporting cultivars.

When the wigwam grown plants reached the top of their wigwams, the plants were left and no additional steps were taken to encourage further growth.

When the wigwam grown plants had reached the top of their supports, there was no where else for the plant to go. The Sweet Pea pictured in this photograph is Lathyrus odoratus 'John Gray'.
When the wigwam grown plants had reached the top of their supports, there was no where else for the plant to go. The Sweet Pea pictured in this photograph is Lathyrus odoratus ‘John Gray’.

This method of growing Sweet Peas is simple and straightforward, it requires very little effort, unlike the labour intensive cordon method of growing Sweet Peas, which requires a great deal more time and effort.  The downside is that the quality of the Sweet Pea flowers produced by wigwam grown plants is inferior than those grown using the cordon method.

The upside is that the Sweet Pea plants and flowers which are grown in this natural way, growing up wigwams for support, have a certain charm and ease about them.  Certainly a wigwam of Sweet Peas is a wonderful addition to the garden, and the time saved from avoiding the work involved in growing Sweet Pea plants using the cordon method can be a blessing if your time is restricted.

Sweet Pea tendrils

Gardeners who grow their Sweet Pea plants in this natural way, growing their plants up wigwams, and leaving the tendrils and side shoots intact, certainly benefit from the addition of the endearing Sweet Pea tendrils, which beautifully embellish the plants and the garden, as well as supporting the plants.

I love growing Lathyrus odoratus naturally up wigwams, the Sweet Pea plants produce such beautiful tendrils, which are a joy to behold.
I love growing Lathyrus odoratus naturally up wigwams, the Sweet Pea plants produce such beautiful tendrils, which are a joy to behold.
In this photograph, a tendril from a wigwam grown Sweet Pea plant, has attached itself to a Sweet Pea flower stem.
In this photograph, a tendril from a wigwam grown Sweet Pea plant, has attached itself to a Sweet Pea flower stem.
All of the Lathyrus odoratus cultivars I grew for my 2016 Sweet Pea Trial were self supporting when grown naturally up wigwam supports.
All of the Lathyrus odoratus cultivars I grew for my 2016 Sweet Pea Trial were self supporting when grown naturally up wigwam supports.
A Lathyrus odoratus tendril that has formed a corkscrew shape. Pictured during my 2016 Sweet Pea Trial.
A Lathyrus odoratus tendril that has formed a corkscrew shape. Pictured during my 2016 Sweet Pea Trial.
A closer look at one of the Sweet Pea tendrils produced by the wigwam grown plants, which were grown for my 2016 Sweet Pea Trial.
A closer look at one of the Sweet Pea tendrils produced by the wigwam grown plants, which were grown for my 2016 Sweet Pea Trial.
Another look at the same Sweet Pea tendril, produced by the wigwam grown plants, which were grown for my 2016 Sweet Pea Trial.
Another look at the same Sweet Pea tendril, produced by the wigwam grown plants, which were grown for my 2016 Sweet Pea Trial.
This Sweet Pea tendril has formed a heart shape. Pictured during my 2016 Sweet Pea Trial.
This Sweet Pea tendril has formed a heart shape. Pictured during my 2016 Sweet Pea Trial.
This Lathyrus odoratus tendril has formed the shape of an 'E'. Pictured during my 2016 Sweet Pea Trial.
This Lathyrus odoratus tendril has formed the shape of an ‘E’. Pictured during my 2016 Sweet Pea Trial.
This Lathyrus odoratus tendril has formed a scroll. Pictured during my 2016 Sweet Pea Trial.
This Lathyrus odoratus tendril has formed a scroll. Pictured during my 2016 Sweet Pea Trial.
A beautiful heart shape formed by the Lathyrus odoratus tendrils. Pictured during my 2016 Sweet Pea Trial.
A beautiful heart shape formed by the Lathyrus odoratus tendrils. Pictured during my 2016 Sweet Pea Trial.

Sweet Pea Cordons

Again the Sweet Pea plants that were grown as cordons, were all planted at the same time, and at the same time as the wigwam grown Sweet Pea plants.

The cordon grown Sweet Pea plants were grown as a double row of cordon grown plants.  The cordon grown Sweet Pea plants were grown and planted individually, where they enjoyed more space between each plant, than the wigwam grown plants, which were planted more closely together.  Each Sweet Pea plant was grown up a tall bamboo cane, each cane was tied into a large Sweet Pea frame for support.  

The cordon Grown Sweet Pea plants were secured in place regularly as they grew up the canes.  The plants were secured to the bamboo canes using metal Sweet Pea rings that I purchased from the National Sweet Pea Society.  I find it easier to use these metal Sweet Pea rings, rather than using a soft twine, which is another alternative you could use to secure the Sweet Pea plants to their supports.  The Sweet Pea rings are especially useful when it comes to layering the plants.  It’s so quick and easy to remove the Sweet Pea rings or to apply them, I have reused these rings countless times with great success.

Cordon grown Sweet Pea plants have their tendrils and side shoots removed.  These plants require tying in regularly, as they are unable to support themselves once their tendrils are removed.  The cordon grown Sweet Pea plants require dedicated and regular attention to regularly remove the tendrils and side shoots, and to secure the plants to their supports.

During the 2016 Sweet Pea Trial, I was mindful of any damage that could occur to the single Sweet Pea cordon stems, consequently for each cordon grown plant I tried to keep a small side shoot available in reserve, as a back up, should the main cordon become damaged.  If the main cordon does become damaged or loses its vigour, it can be cut out and another side shoot can then take over.  This is a useful strategy to adopt when growing Sweet Peas following the cordon growing method, and is something I would advise you to consider if you plan to grow Sweet Pea plants in this way.

The cordon growing method encourages the Sweet Pea plant’s energy to focus on producing flowers.  The cordon grown Sweet Pea plants receive more light and better air circulation that the plants grown naturally up wigwams.  The quality of the flowers grown using the cordon method is superior to that of wigwam grown plants.  Cordon grown plants produce larger flowers and a greater number of blooms per flowering stem.

Sweet Pea cordons.
Sweet Pea cordons.

Layering cordon grown Sweet Pea plants

When the cordon grown Sweet Pea plants had reached the top of their bamboo canes, the Sweet Pea plants were then layered.  The Sweet Pea plants’ metal Sweet Pea rings were removed, so the Sweet Pea plants could be removed from their canes, and gently laid on the ground, where they were then directed to grow up another bamboo cane.  By layering the Sweet Pea plants, it further encourages the Sweet Pea plants to grow and flower.  Layering reinvigorates the plant.

It’s advisable to thoroughly weed the area around your Sweet Pea plants prior to layering, as naturally this area will be covered with plant stems and will be difficult, if not impossible to weed after the plants have been layered.

The cordon method of growing Sweet Pea plants is clearly far more labour intensive and time consuming than simply growing the Sweet Pea plants up wigwams, which requires very little effort.

The quality of the Sweet Pea flowers produced by cordon grown plants is superior to that of the more naturally grown flowers.  Sweet Pea growers who grow Sweet Pea flowers for exhibition or to show, always use the cordon method to grow their plants.

Sweet Pea flowers

The first flowers to be picked for the 2016 Sweet Pea trial were Lathyrus odoratus ‘Windsor’ and Lathyrus odoratus ‘John Gray’.  These first blooms were picked on the 12th June 2016 – this is by far the latest date that I have ever harvested my first Sweet Pea flowers of the year.  The Sweet Pea plants that produced the first flowers were sown on the 26th October 2015 – L. odoratus ‘Windsor’, and on the 13th February 2016 – L. odoratus ‘John Gray’.

Once the Sweet Pea plants started flowering they were checked each and every single day of the trial.  Any open flowers present were then cut, the flower stems were measured, and the Sweet Pea flowers were photographed separately for each of the two growing methods.  The results were recorded in this way, so that the growing methods, and the time of sowing could be compared.

It’s important to pick your Sweet Pea flowers.  Regularly harvested plants have more energy to be able to produce their maximum number of flowers.  If the Sweet Pea flowers are not picked, and the blooms are left on the plants, they will quickly run to seed, flowering will cease, and the plants will die.

The last flower to be harvested from the 2016 Sweet Pea Trial was picked on the 13th September 2016 – this is one of the earliest dates that my Sweet Pea Trial has closed.  A Lathyrus odoratus ‘John Gray’ bloom was the last flower to be harvested for the 2016 Sweet Pea Trial, this plant was sown on the 12th March 2016.

This video shows the flowers picked on each day throughout the trial, split by growing method.

2016 Sweet Pea Trial Weather Conditions

This chart plots the min and max daily temperature for the germination and seedling stages of the plants. Each red line indicates a sowing date (10th Oct, 26th Oct, 2nd Jan, 13th Feb, 12th Mar). The best performing sowing dates (in terms of number of flowers) were January and February, both of which were followed by a number of sub-zero temperatures; however, there doesn't seem to be any specific patterns that would indicate temperature having a significant impact on the plants' flowering performance later in the year from the data I have collated here.
This chart plots the min and max daily temperature for the germination and seedling stages of the plants. Each red line indicates a sowing date (10th Oct, 26th Oct, 2nd Jan, 13th Feb, 12th Mar). The best performing sowing dates (in terms of number of flowers) were January and February, both of which were followed by a number of sub-zero temperatures; however, there doesn’t seem to be any specific patterns that would indicate temperature having a significant impact on the plants’ flowering performance later in the year from the data I have collated here.
This chart plots the rainfall for the germination and seedling stages of the plants. Each red line indicates a sowing date (10th Oct, 26th Oct, 2nd Jan, 13th Feb, 12th Mar). The best performing sowing dates (in terms of number of flowers) were January and February. It's possible that the lower rainfall after sowing contributed to stronger plants. In particular, both October sowings had to contend with almost constant daily rain for the 2 months following their sowing. However, it's difficult to draw any significant conclusions from this data.
This chart plots the rainfall for the germination and seedling stages of the plants. Each red line indicates a sowing date (10th Oct, 26th Oct, 2nd Jan, 13th Feb, 12th Mar). The best performing sowing dates (in terms of number of flowers) were January and February. It’s possible that the lower rainfall after sowing contributed to stronger plants. In particular, both October sowings had to contend with almost constant daily rain for the 2 months following their sowing. However, it’s difficult to draw any significant conclusions from this data.

Although the young Sweet Pea seedlings inevitably endured periods of drought and stress during the earlier stages of the 2016 Sweet Pea Trial, these stresses were minimised somewhat due to the water holding capacity of the compost used.  The only negative effect of using Dalefoot Composts Wool Compost is that during periods of very inclement weather, the potential for damping off, or rotting of the seeds and seedlings is increased, due to the water holding capacity of the compost, combined with the prolonged rainfall and wet conditions.  This negative could have been reduced, had a shelter been erected to protect the seedlings during inclement weather, and then removed once the weather brightened.  Naturally, the problems caused by drought, could be erased by regular watering during periods of dry conditions.

Sweet Pea Pests

I didn’t apply any preventative sprays for pests, I didn’t spray the Sweet Pea plants at all, even when pests arrived.  The only precaution I took to prevent pest damage to my 2016 Sweet Pea Trial, was to soak the Sweet Pea seeds for a moment, in liquid paraffin, prior to sowing, to deter mice from eating the seeds.

Aphids

All of the Sweet Pea plants suffered from infestations of aphids, also known as greenfly.  Aphids are a commonly found, sap sucking insect that feed on the sap of the Sweet Peas (and many other plants!).  The aphids feed through the Sweet Pea plant’s leaves, stems and flowers.  The resulting damage and nutrient loss weakens plants, resulting in distortion and stunted growth.

An aphid infestation on my 2016 Sweet Pea Trial plants.
An aphid infestation on my 2016 Sweet Pea Trial plants.

Sweet Pea plants are prone to suffer with viruses.  Aphids are virus vectors – they can transmit viral diseases from one plant to another, quickly infecting plants, and spreading disease.  Aphids are a consequently a serious pest of Sweet Peas and cause significant damage.  As aphids feed on the sap from plants, they excrete honeydew, a sugary sticky substance on which dark, sooty moulds readily form, hampering the plant’s ability to photosynthesise and making the plants look unsightly.

Another image of an aphid infestation on the Lathyrus odoratus plants, which were grown for my 2016 Sweet Pea trial.
Another image of an aphid infestation on the Lathyrus odoratus plants, which were grown for my 2016 Sweet Pea trial.

Aphids have many predators including birds, ladybirds, ladybird larvae, lacewing larvae, spiders, and parasitic wasps.

Although this Lathyrus odoratus leaf and stem may at first glance look as if they are covered in whitefly, in fact this leaf is decorated with the dead, discarded skins of aphids, which have been shed as the aphids have grown in size.
Although this Lathyrus odoratus leaf and stem may at first glance look as if they are covered in whitefly, in fact this leaf is decorated with the dead, discarded skins of aphids, which have been shed as the aphids have grown in size.

Caterpillars

I discovered a few caterpillars feeding on my 2016 Sweet Pea Trial plants.  The caterpillars didn’t cause any noticeable damage.  I left the caterpillars alone, I made no attempts to remove them.  I watched a variety of different birds, including long-tailed tits, blue tits, and coal tits removing and eating the caterpillars on the Sweet Pea plants, which could explain the lack of damage to the plants – the caterpillars were eaten before they became a problem.

Here's a caterpillar I found during my 2016 Sweet Pea Trial. The caterpillars I found on the Sweet Pea plants, were different types of caterpillar, but they were all well camouflaged with their green colouring, which helped the caterpillars to be less noticeable on the plants.
Here’s a caterpillar I found during my 2016 Sweet Pea Trial. The caterpillars I found on the Sweet Pea plants, were different types of caterpillar, but they were all well camouflaged with their green colouring, which helped the caterpillars to be less noticeable on the plants.
Here's another caterpillar I found on my Sweet Pea plants. This caterpillar when it's fully grown will create a pupae, the caterpillar transforms inside the pupae, and eventually will emerge as a moth.
Here’s another caterpillar I found on my Sweet Pea plants. This caterpillar when it’s fully grown will create a pupae, the caterpillar transforms inside the pupae, and eventually will emerge as a moth.

Slugs and Snails

Cornu aspersum - the commonly seen garden snail, pictured on my Sweet Pea wigwams, during my 2016 Sweet Pea Trial.
Cornu aspersum – the commonly seen garden snail, pictured on my Sweet Pea wigwams, during my 2016 Sweet Pea Trial.

For my 2015 Sweet Pea Trial I used a copper tape, which I wrapped around each leg of my Rootrainers Racking Station to deter slugs and snails from climbing the Racking Station and devouring the Sweet Pea plants – which was my greatest worry at this first stage of the trial.  I found that soon after I had applied the copper tape, it tarnished rapidly, as the copper oxidised, thus I found the copper tape was then ineffective as a slug and snail deterrent.  As the copper tape was expensive, and the copper itself was only effective for a very fleeting time period, this year I skipped this step.  I did not install any deterrents for slugs or snails at any stage of my 2016 Sweet Pea Trial.

Cornu aspersum - the commonly seen garden snail, pictured on Lathyrus odoratus leaves, during my 2016 Sweet Pea Trial.
Cornu aspersum – the commonly seen garden snail, pictured on Lathyrus odoratus leaves, during my 2016 Sweet Pea Trial.

I did see quite a number of snails and slugs during the course of the trial, but they caused very little noticeable damage to my plants.  I noticed that the numbers of slugs and snails encountered during this trial had increased from the previous year.  I was happy to let these little creatures eat some of the leaves from my Sweet Pea plants, and I did not attempt to remove the slugs or snails.  No month of sowing provided any greater slug or snail protection than another, and all plants received the same amount of damage, i.e. very little.

The snails I encountered during my 2016 Sweet Pea Trial caused very little damage to my Sweet Pea plants.
The snails I encountered during my 2016 Sweet Pea Trial caused very little damage to my Sweet Pea plants.

It is possible that the Sweet Pea plants grown as cordons experienced slightly less slug and snail damage, as the cordon plants are grown with a larger gap between each plant.  The cordon grown plants are therefore more open to the elements, and as a consequence any slugs or snails present on these plants would have been more visible to predators such as beetles, birds, frogs, toads, hedgehogs, slow worms etc.

Two white lipped snails, also known as Cepaea hortensis, on the leaves of Lathyrus odoratus, pictured during my 2016 Sweet Pea trial.
Two white lipped snails, also known as Cepaea hortensis, on the leaves of Lathyrus odoratus, pictured during my 2016 Sweet Pea trial.
A pretty Cepaea hortensis, or white lipped snail resting on the Sweet pea wigwams during my 2016 Sweet Pea Trial.
A pretty Cepaea hortensis, or white lipped snail resting on the Sweet pea wigwams during my 2016 Sweet Pea Trial.

Beneficial Insects

Fortunately many insectivorous insects predated on the aphid colonies and infestations that established themselves on the Lathyrus odoratus plants grown for my 2016 Sweet Pea Trial.  Though sadly during the 2016 growing season, I noticed that these beneficial insects made a later arrival in 2016, than they had in 2015.

I noted that the hoverfly larvae arrived first to control the aphids, followed by the lacewing larvae, and finally, with quite a break in between, the ladybirds and ladybird larvae made their presence known.  Consequently, the aphids enjoyed an extended period of largely unhindered establishment on the Lathyrus odoratus plants before the hoverfly larvae, lacewing larvae, and ladybirds with their larvae, arrived to control their numbers.

Hoverflies

A number of different hoverfly species were spotted on the Lathyrus odoratus plants grown for my 2016 Sweet Pea Trial. This hoverfly is called Myathropa florea, but is more commonly known as the Batman hoverfly due to the bat like marking on the fly’s thorax.
A hoverfly resting on one of the Sweet Pea wigwams, used for the 2016 Sweet Pea Trial.
A hoverfly resting on one of the Sweet Pea wigwams, used for the 2016 Sweet Pea Trial.

A variety of different hoverflies were spotted on the Sweet Pea plants.  The insects were spotted equally on both the cordon grown plants and the wigwam grown plants, no preference for either growing method was noted.

A number of different hoverfly species were spotted on the Lathyrus odoratus plants grown for my 2016 Sweet Pea Trial.
A number of different hoverfly species were spotted on the Lathyrus odoratus plants grown for my 2016 Sweet Pea Trial.
A hoverfly resting on a Sweet Pea leaf that has a covering of powdery mildew over the surface of the leaf.
A hoverfly resting on a Sweet Pea leaf that has a covering of powdery mildew over the surface of the leaf.

Many species of hoverfly larvae are predators of aphids, so it was wonderful to see so many hoverflies laying eggs on the Sweet Pea plants grown for my trial.

A marmalade hoverfly, also known by its scientific name of Episyrphus balteatus, laying eggs on a Lathyrus odoratus flower stem.
A marmalade hoverfly, also known by its scientific name of Episyrphus balteatus, laying eggs on a Lathyrus odoratus flower stem.
Episyrphus balteatus, also known by its common name of marmalade hoverfly, laying eggs on a Sweet Pea tendril produced by one of the wigwam grown Sweet Pea plants, which were grown for my 2016 Sweet Pea Trial.
Episyrphus balteatus, also known by its common name of marmalade hoverfly, laying eggs on a Sweet Pea tendril produced by one of the wigwam grown Sweet Pea plants, which were grown for my 2016 Sweet Pea Trial.
A marmalade hoverfly, also known by its scientific name of Episyrphus balteatus, laying eggs on a Lathyrus odoratus 'Misty' flower bud, that is covered by a vast colony of aphids.
A marmalade hoverfly, also known by its scientific name of Episyrphus balteatus, laying eggs on a Lathyrus odoratus ‘Misty’ flower bud, that is covered by a vast colony of aphids.

Hoverfly Larvae

A variety of different hoverfly larvae were found on the Sweet Pea plants grown for the 2016 Sweet Pea Trial.  The hoverfly larvae that were spotted on the Sweet Pea plants during the 2016 Sweet Pea Trial were insectivores, they predated on the aphids found on the Sweet Pea plants.

A hoverfly larvae predating on an aphid on a Lathyrus odoratus leaf.
A hoverfly larvae predating on an aphid on a Lathyrus odoratus leaf.

The hoverfly larvae were the first beneficial insect to be found on the Sweet Pea plants grown for the 2016 Sweet Pea Trial.

A hoverfly larvae on a Lathyrus odoratus leaf that is displaying evidence of the damage the aphid colonies have caused the plant. The white objects are the dead skins that the aphids have shed and discarded as they have grown, sometimes these dead skins are mistaken for whitefly, due to their similar appearance.
A hoverfly larvae on a Lathyrus odoratus leaf that is displaying evidence of the damage the aphid colonies have caused the plant. The white objects are the dead skins that the aphids have shed and discarded as they have grown, sometimes these dead skins are mistaken for whitefly, due to their similar appearance.
A hoverfly larvae on a Lathyrus odoratus leaf. Pictured during my 2016 Sweet Pea Trial.
A hoverfly larvae on a Lathyrus odoratus leaf. Pictured during my 2016 Sweet Pea Trial.

A quantity of the hoverfly larvae found on the Sweet Pea plants were eaten by birds, but many of the larvae did grow to full term, as I spotted a large number of hoverfly pupa both on the Sweet Pea plants and their supports.

A hoverfly pupa attached to a Lathyrus odoratus plant. Pictured during my 2016 Sweet Pea trial.
A hoverfly pupa attached to a Lathyrus odoratus plant. Pictured during my 2016 Sweet Pea trial.

Lacewings

Green lacewings were spotted a few times on the Sweet Pea plants.  I expect the lacewings were often present on the Sweet Pea plants, but due to their nocturnal habit, they were only spotted on occasion.

A green lacewing resting on a Sweet Pea plant, grown for my 2016 Sweet Pea Trial.
A green lacewing resting on a Sweet Pea plant, grown for my 2016 Sweet Pea Trial.

Lacewing Larvae

A number of lacewing larvae were found on the Sweet Pea plants.  Another insectivorous insect, lacewing larvae predate on aphids.  Again the lacewing larvae were spotted late into the trial, arriving shortly after the hoverfly larvae, but before the ladybird, which was the last insectivorous insect to arrive.

Aphids often colonise the undersides of plant leaves where they are less visible to predators. In this photograph, you can see a number of lacewing larvae predating on an aphid colony gathered on the underside of a Lathyrus odoratus leaf.
Aphids often colonise the undersides of plant leaves where they are less visible to predators. In this photograph, you can see a number of lacewing larvae predating on an aphid colony gathered on the underside of a Lathyrus odoratus leaf.
A closer look at an aphid colony present on the underside of an Lathyrus odoratus leaf. The white objects in the picture are the shed skins of the aphids, and the brown insects of varying sizes are lacewing larvae at differing stages of development.
A closer look at an aphid colony present on the underside of an Lathyrus odoratus leaf. The white objects in the picture are the shed skins of the aphids, and the brown insects of varying sizes are lacewing larvae at differing stages of development.
A lacewing larvae predating on an aphid on a Lathyrus odoratus 'John Gray' flower.
A lacewing larvae predating on an aphid on a Lathyrus odoratus ‘John Gray’ flower.
Another lacewing larvae and a small group of aphids, this time spotted on a rather tatty Lathyrus odoratus 'Misty' flower.
Another lacewing larvae and a small group of aphids, this time spotted on a rather tatty Lathyrus odoratus ‘Misty’ flower.

Ladybirds

One of the ladybirds spotted during the 2016 Sweet Pea trial.
One of the ladybirds spotted during the 2016 Sweet Pea trial.

A variety of different ladybird species were seen on the Sweet Pea plants grown for the 2016 Sweet Pea Trial.  Sadly the ladybirds were very late in arriving, I spotted the first ladybird on the Sweet Pea plants in mid-July 2016.  Once they did arrive the ladybirds quickly established themselves, and were spotted feasting on aphids, mating, and laying eggs.

Ladybirds mating on the 2016 Sweet Pea Trial bamboo canes.
Ladybirds mating on the 2016 Sweet Pea Trial bamboo canes.
Ladybird eggs on the underside of a Lathyrus odoratus leaf. Pictured during my 2016 Sweet Pea Trial.
Ladybird eggs on the underside of a Lathyrus odoratus leaf. Pictured during my 2016 Sweet Pea Trial.
A ladybird feasting on an aphid, that's part of a colony on the wigwam grown Lathyrus odoratus plants, grown for my 2016 Sweet Pea Trial.
A ladybird feasting on an aphid, that’s part of a colony on the wigwam grown Lathyrus odoratus plants, grown for my 2016 Sweet Pea Trial.
A ladybird resting on a Lathyrus odoratus leaf that has a covering of powdery mildew.
A ladybird resting on a Lathyrus odoratus leaf that has a covering of powdery mildew.

Ladybird Larvae

A ladybird larvae on a bamboo cane in the 2016 Sweet Pea Trials area.
A ladybird larvae on a bamboo cane in the 2016 Sweet Pea Trials area.

Ladybird larvae are also insectivores, they predate on aphids.  Although the ladybirds were late in arriving at the Sweet Pea plants, once they had arrived, the ladybirds quickly mated, laid eggs, and produced young, which rapidly controlled the numbers of aphids present on the Sweet Pea plants.  Sadly this happened late in the growing period, and the Sweet Pea plants were by this stage already significantly weakened by the large infestations of aphids that had colonised the plants from fairly early on in the trial, when the insectivorous insects were not present.

A Ladybird larvae residing on a cordon grown Lathyrus odoratus stem. Pictured during my 2016 Sweet Pea Trial.
A Ladybird larvae residing on a cordon grown Lathyrus odoratus stem. Pictured during my 2016 Sweet Pea Trial.
Both adult ladybirds and their larvae predate on aphids, they are valuable allies for gardeners. This ladybird larvae was pictured on Lathyrus odoratus during the 2016 Sweet Pea Trial.
Both adult ladybirds and their larvae predate on aphids, they are valuable allies for gardeners. This ladybird larvae was pictured on Lathyrus odoratus during the 2016 Sweet Pea Trial.
A Ladybird larvae pictured on a Lathyrus odoratus leaf, during the 2016 Sweet Pea Trial.
A Ladybird larvae pictured on a Lathyrus odoratus leaf, during the 2016 Sweet Pea Trial.

Spiders

A range of garden spiders were present at every stage of the 2016 Sweet Pea Trial.  The spiders were successful in catching aphids, flies, and other insects, in the webs they produced around the plants.

A variety of different spiders helped to control the number of aphids found on the Sweet Pea plants during the 2016 Sweet Pea Trial.
A variety of different spiders helped to control the number of aphids found on the Sweet Pea plants during the 2016 Sweet Pea Trial.

Birds

A variety of different garden birds visited the Sweet Pea plants grown for the 2016 Sweet Pea Trial each day.  I watched long-tailed tits, blue tits, coal tits, and great tits, surveying the plants, removing and eating aphids, caterpillars, and hoverfly larvae too.  The birds were always very welcome, in the earlier stages of the 2016 Sweet Pea Trial it seemed as if these beautiful garden birds were the only predator of the aphids that had colonised the Sweet Pea plants.

During the 2016 Sweet Pea Trial, the birds that visited the Sweet Pea plants caused no damage to the plants.

A Long-tailed tit, also known by its scientific name of Aegithalos caudatus, pictured on the Sweet Pea wigwams.
A Long-tailed tit, also known by its scientific name of Aegithalos caudatus, pictured on the Sweet Pea wigwams.

Other insects

Common Green Shield Bugs

Common Green Shield Bug nymphs in various stages of development were spotted on the Sweet Pea plants, their numbers increased as the growing season came to a close.

A Common Green Shield Bug nymph, also known by its scientific name of Palomena prasina resting on a dead Lathyrus odoratus leaf.
A Common Green Shield Bug nymph, also known by its scientific name of Palomena prasina resting on a dead Lathyrus odoratus leaf.

Pollen beetle

Here you can see a tiny pollen beetle, a Meligethes species, crawling over a Lathyrus odoratus 'John Gray' bloom.
Here you can see a tiny pollen beetle, a Meligethes species, crawling over a Lathyrus odoratus ‘John Gray’ bloom.

Pollen beetles were also spotted on the flowers grown for the 2016 Sweet Pea Trial.  Pollen beetles, as you might expect, feed on pollen, these tiny beetles are particularly drawn to yellow coloured flowers, they favour oil seed rape as a food source, but can be found on a range of plants.  Pollen beetles are fond of Sweet Pea pollen, and they can often be seen foraging around inside the keel of the Sweet Pea flower.  Many Sweet Pea growers find these beetles irritating and unsightly.  Usually I find that if I unintentionally bring any pollen beetles indoors with my Sweet Pea flowers, the pollen beetles quickly head for a window, naturally keen to get back outside.  I personally don’t find pollen beetles to be a great nuisance, I don’t mind these tiny insects eating the pollen from my plants.

Sweet Pea diseases

Powdery mildew

Powdery mildew is a fungal disease that affects the leaves and occasionally the stems of Sweet Pea plants, though it’s usually noticed on the leaves, where it forms a white powdery coating over the surface of the leaves.

Powdery mildews are often host specific, and only spread to other plants of the same, or a very closely related species.  So if you discover powdery mildew on your Sweet Pea plants, you won’t find this strain of powdery mildew spreading to your Rhododendrons, apples or roses.  Though of course these plants could all suffer with their own powdery mildews at the same time!

This photograph was taken on the 18th June 2016. Here you can see that powdery mildew has begun to establish itself on the Lathyrus odoratus plants. This is Lathyrus odoratus 'Ida King' which has been grown as a cordon, this was the first plant to become susceptible to powdery mildew in the 2016 Sweet Pea trial.
This photograph was taken on the 18th June 2016. Here you can see that powdery mildew has begun to establish itself on the Lathyrus odoratus plants. This is Lathyrus odoratus ‘Ida King’ which has been grown as a cordon, this was the first plant to become susceptible to powdery mildew in the 2016 Sweet Pea trial.
By the 26th June 2016, powdery mildew was also present on the wigwam grown Sweet Pea plants.
By the 26th June 2016, powdery mildew was also present on the wigwam grown Sweet Pea plants.

As with any fungal disease, minimising the spread of the spores can help to reduce further infection, so removing infected leaves as soon as powdery mildew is noticed, and removing all leaves promptly at the end of the season, in order to reduce infection the following year will help a little.

Applying a thick mulch around the Sweet Pea plants, and ensuring that the plants have always have sufficient water and nutrients, generally by ensuring that the Sweet Pea plants are grown as well as possible, can also help to alleviate or delay the symptoms of powdery mildew.  Some Lathyrus odoratus hybrid cultivars which have an increased resistance to mildew are available.  Though the powdery mildews do also evolve, and some cultivars that have previously displayed a resistance, over time may become more susceptible.

Here you can see a more considerable covering of powdery mildew on the Lathyrus odoratus plants. Though, looking on the bright side, these Lathyrus odoratus tendrils have formed a beautiful heart shape. Pictured during my 2016 Sweet Pea Trial.
Here you can see a more considerable covering of powdery mildew on the Lathyrus odoratus plants. Though, looking on the bright side, these Lathyrus odoratus tendrils have formed a beautiful heart shape. Pictured during my 2016 Sweet Pea Trial.

Other Sweet Pea problems

Bud drop

Bud drop is a commonly experienced condition when growing Sweet Peas.  The affected Sweet Pea flower bud turns a lighter pale yellow-green, before the flower bud drops off leaving an empty stem.  Once you’ve experienced bud drop it’s easy to spot any lighter coloured flower buds that aren’t going to make it.  As soon as I notice any flower stems showing signs of bud drop, I promptly remove all the affected flower stems – this prevents the plant from wasting excess energy on a flower stem which will not bloom.

Bud drop is a commonly experienced condition on Sweet Pea plants. The Sweet Pea flower buds turn a pale yellow-green, as you can see in this picture, and drop off before opening. Once you have encountered bud drop, it's easy to recognise the early signs of the condition. I remove any of the affected flower stems as soon as I notice them.
Bud drop is a commonly experienced condition on Sweet Pea plants. The Sweet Pea flower buds turn a pale yellow-green, as you can see in this picture, and drop off before opening. Once you have encountered bud drop, it’s easy to recognise the early signs of the condition. I remove any of the affected flower stems as soon as I notice them.

Bud drop was experienced in equal measure by both the Sweet Pea plants grown as cordons, and those grown naturally up wigwams.  No growing method prevented or encouraged the condition.

2016 Sweet Pea Trial Results

The quantity of Sweet Pea flowers harvested

This chart shows the number of flowers picked for each variety, with each column broken up to indicate the proportion of flowers from each sowing. As you can see, Lathyrus odoratus 'Aphrodite' had the most flowers, with over 275 stems harvested during the trial. Lathyrus odoratus 'Ida King' had the fewest flowers, with under 100 flower stems harvested during the trial.
This chart shows the number of flowers picked for each variety, with each column broken up to indicate the proportion of flowers from each sowing. As you can see, Lathyrus odoratus ‘Aphrodite’ had the most flowers, with over 275 stems harvested during the trial. Lathyrus odoratus ‘Ida King’ had the fewest flowers, with under 100 flower stems harvested during the trial.
This chart shows the daily count of harvested Sweet Pea flowers, broken down by variety.
This chart shows the daily count of harvested Sweet Pea flowers, broken down by variety.
This chart shows the number of flowers picked each day, but sub-divided by sowing date. It's clear from the chart that the 2nd January 2016, and the 13th February 2016, produced more flowers than any other sowing, but this is likely to be because more plants from these sowings survived. When the data is normalised for the number of plants, the 12th March 2016 is the second best performer (see other chart).
This chart shows the number of flowers picked each day, but sub-divided by sowing date. It’s clear from the chart that the 2nd January 2016, and the 13th February 2016, produced more flowers than any other sowing, but this is likely to be because more plants from these sowings survived. When the data is normalised for the number of plants, the 12th March 2016 is the second best performer (see other chart).
This chart shows the total number of flowers for each sowing date. Here you can see that Sweet Pea plants sown on the 13th February 2016 significantly outperformed the other sowing times, with nearly 200 more flowers produced by these plants than the second-best, the 2nd January 2016 sown plants. The Sweet Pea plants sown on the 10th October 2015 have produced a very small number of flowers, due to the low survival rate of the plants prior to planting out. Even so, as you can see in the normalised chart, even when accounting for that, the 10th October 2016 is still the worst-performing sowing from my 2016 Sweet Pea Trial.
This chart shows the total number of flowers for each sowing date. Here you can see that Sweet Pea plants sown on the 13th February 2016 significantly outperformed the other sowing times, with nearly 200 more flowers produced by these plants than the second-best, the 2nd January 2016 sown plants. The Sweet Pea plants sown on the 10th October 2015 have produced a very small number of flowers, due to the low survival rate of the plants prior to planting out. Even so, as you can see in the normalised chart, even when accounting for that, the 10th October 2016 is still the worst-performing sowing from my 2016 Sweet Pea Trial.
This chart shows the number of flowers per sowing date, normalised for the number of plants that survived to be planted. This shows that if more plants from the 12th March 2016 sowing had survived, these plants would have fared much better, as the flowering rates per plant were second-best. The Feb/Mar sowings had a flowering rate which was nearly three times greater than that of the plants sown in October 2015.
This chart shows the number of flowers per sowing date, normalised for the number of plants that survived to be planted. This shows that if more plants from the 12th March 2016 sowing had survived, these plants would have fared much better, as the flowering rates per plant were second-best. The Feb/Mar sowings had a flowering rate which was nearly three times greater than that of the plants sown in October 2015.
This chart shows the total number of flowers picked per variety, but normalised for the number of plants - an extrapolation of the number of flowers expected if the number of plants was equal across all varieties. Lathyrus odoratus 'Naomi Nazareth' was the top performer, with over double the flowering rate of the worst performer, Lathyrus odoratus 'Lady Nicholson'.
This chart shows the total number of flowers picked per variety, but normalised for the number of plants – an extrapolation of the number of flowers expected if the number of plants was equal across all varieties. Lathyrus odoratus ‘Naomi Nazareth’ was the top performer, with over double the flowering rate of the worst performer, Lathyrus odoratus ‘Lady Nicholson’.

Sweet Pea flower stem lengths

After reading my 2015 Sweet Pea Trial Report, Roger Parsons suggested that I introduce a minimum usable stem length, and apply this to my results, to filter out all of the very short stemmed flowers.  Taking Roger’s advice, I looked at an array of Sweet Pea flowers to establish what I felt would be a satisfactory minimum usable stem length.  I opted for 15cm (6″) as my minimum usable stem length, as this length of stem allowed the Sweet Pea flowers to be placed in a regular sized jam jar, where their size was in proportion to the vessel.

This chart shows the distribution of usable stems over time. Assuming a 'usable' stem is 15cm or longer (for display in a vase), you can see that initially the majority of stems are usable. However, towards the end of July, the number of short stems starts to creep up, and increases throughout August. Even though there are 10-15 flowers to pick each day in the last week of August, many of them are too short to display in a vase.
This chart shows the distribution of usable stems over time. Assuming a ‘usable’ stem is 15cm or longer (for display in a vase), you can see that initially the majority of stems are usable. However, towards the end of July, the number of short stems starts to creep up, and increases throughout August. Even though there are 10-15 flowers to pick each day in the last week of August, many of them are too short to display in a vase.
This chart shows the average flower stem length produced by each growing method. As expected, the plants grown as cordons have produced significantly longer flower stems - on average 5cm longer, than the flowers produced by the plants grown on wigwams. This is a good demonstration of why cordon grown Sweet Pea flowers are better for the show bench.
This chart shows the average flower stem length produced by each growing method. As expected, the plants grown as cordons have produced significantly longer flower stems – on average 5cm longer, than the flowers produced by the plants grown on wigwams. This is a good demonstration of why cordon grown Sweet Pea flowers are better for the show bench.
This chart shows the average stem length per day for both growing methods. As well as demonstrating the clear advantage of cordons for longer stems, it also shows that the peak dates for harvesting Sweet Pea flowers with long stems are in early July, after which the stem lengths begin to shorten significantly.
This chart shows the average stem length per day for both growing methods. As well as demonstrating the clear advantage of cordons for longer stems, it also shows that the peak dates for harvesting Sweet Pea flowers with long stems are in early July, after which the stem lengths begin to shorten significantly.
This chart shows the average stem length by sowing date. Again, the 12th February 2016 and the 2nd January 2016, are out in front, with an average stem length nearly 5cm longer than the worst performing sowing.
This chart shows the average stem length by sowing date. Again, the 12th February 2016 and the 2nd January 2016, are out in front, with an average stem length nearly 5cm longer than the worst performing sowing.
This chart shows the average stem length by variety. There isn't a huge difference between the best and the worst - around 3-4cm difference.
This chart shows the average stem length by variety. There isn’t a huge difference between the best and the worst – around 3-4cm difference.
This chart shows the longest individual stem length for each variety. Lathyrus odoratus 'John Gray' was the winner, with a whopping 48cm flower stem. At the other end of the scale, the longest flower stem that Lathyrus odoratus 'Lady Nicholson' produced was only 30cm in length.
This chart shows the longest individual stem length for each variety. Lathyrus odoratus ‘John Gray’ was the winner, with a whopping 48cm flower stem. At the other end of the scale, the longest flower stem that Lathyrus odoratus ‘Lady Nicholson’ produced was only 30cm in length.
This chart shows stem length tracked against the maximum daily temperature. There is no correlation, so it's clear that hotter weather does not give any improvement in stem length.
This chart shows stem length tracked against the maximum daily temperature. There is no correlation, so it’s clear that hotter weather does not give any improvement in stem length.

Evaluating the different growing methods – cordons and wigwams

This chart shows the number of flowers picked each day, split by growing method. In terms of flowers-per-day, the cordons outperformed the wigwams on most of the days, and more flowers were picked from the cordons overall.
This chart shows the number of flowers picked each day, split by growing method. In terms of flowers-per-day, the cordons outperformed the wigwams on most of the days, and more flowers were picked from the cordons overall.
This chart shows the total number of flowers normalised for the number of plants - i.e., the number of expected flowers if all seeds had germinated and survived to be planted out, grown and then flowered. After normalising, the wigwams come out on top, which demonstrates that although fewer wigwam plants survived, the rate of flowering per plant was much higher for the wigwams. This is to be expected; cordon grown plants have a lower flowing rate, but produce better quality flowers with longer stems.
This chart shows the total number of flowers normalised for the number of plants – i.e., the number of expected flowers if all seeds had germinated and survived to be planted out, grown and then flowered. After normalising, the wigwams come out on top, which demonstrates that although fewer wigwam plants survived, the rate of flowering per plant was much higher for the wigwams. This is to be expected; cordon grown plants have a lower flowing rate, but produce better quality flowers with longer stems.

 

This chart shows the total number of flowers produced by both the plants grown as wigwams, and as cordons. The numbers of flowers are broken down by variety. Cordons just edge ahead on numbers, but perhaps the most fascinating observation is how close the number of flowers produced by each growing method is for each variety. For example, the Lathyrus odoratus 'Aphrodite' plants grown as cordons produced 142 flowers, and the Lathyrus odoratus 'Aphrodite' plants grown as wigwams also produced 142 flowers.
This chart shows the total number of flowers produced by both the plants grown as wigwams, and as cordons. The numbers of flowers are broken down by variety. Cordons just edge ahead on numbers, but perhaps the most fascinating observation is how close the number of flowers produced by each growing method is for each variety. For example, the Lathyrus odoratus ‘Aphrodite’ plants grown as cordons produced 142 flowers, and the Lathyrus odoratus ‘Aphrodite’ plants grown as wigwams also produced 142 flowers.

Weather conditions

This chart shows the total number of flowers picked, alongside the min/max daily temperature. It's difficult to spot any significant correlation, so it would appear that warmer temperatures do not result in an increase in flowers.
This chart shows the total number of flowers picked, alongside the min/max daily temperature. It’s difficult to spot any significant correlation, so it would appear that warmer temperatures do not result in an increase in flowers.
This chart shows the rainfall in centimeters throughout the trial period. You can see that after the 23rd July 2016, there was very little rain until September. However, all of the plants grown for this trial were watered with an automatic watering system.
This chart shows the rainfall in centimeters throughout the trial period. You can see that after the 23rd July 2016, there was very little rain until September. However, all of the plants grown for this trial were watered with an automatic watering system.
This chart shows the temperature ranges throughout the period of the trial. The top line represents the daily temperature highs, and the bottom line, the daily temperature lows.
This chart shows the temperature ranges throughout the period of the trial. The top line represents the daily temperature highs, and the bottom line, the daily temperature lows.

Conclusions

  • Adopting the cordon method to grow Sweet Pea plants produces fewer flowers than growing Sweet Peas naturally, using wigwams as supports, but the flowers produced by the cordon grown plants are of better quality, having longer stems (nearly 5cm longer on average), larger sized blooms, and more blooms per flowering stem.  
  • Growing Sweet Peas naturally using a wigwam as a support produces 8-10% more flowers, but the naturally grown plants produce blooms which have shorter stems and smaller flowers, with fewer blooms on each flower stem.
  • Lathyrus odoratus ‘Aphrodite’ produced the most flowers during the 2016 Sweet Pea Trial.
  • Lathyrus odoratus ‘Naomi Nazareth’ demonstrated the highest flowering rate per plant, closely followed by L. odoratus ‘Windsor’, L. odoratus ‘Pip’s Cornish Cream’ and L. odoratus ‘Aphrodite’.
  • The Sweet Pea variety that produced the fewest blooms was Lathyrus odoratus ‘Lady Nicholson’ when normalising for flowering rates.  Lathyrus odoratus ‘Ida King’ produced the least flowers overall.
  • The Sweet Pea plants sown on the 13th February 2016 produced flowers with the longest average stem length.
  • The Sweet Pea variety that produced flowers with the longest average stem length over the duration of the 2016 Sweet Pea Trial was Lathyrus odoratus ‘Misty’.
  • The Sweet Pea variety that produced flowers with the shortest average stem length during the 2016 Sweet Pea Trial was Lathyrus odoratus ‘Lady Nicholson’ – with an average stem length nearly 4cm shorter than L. odoratus ‘Misty’.
  • The longest flower stem produced during the 2016 trial was a Lathyrus odoratus ‘John Gray’, with a 48cm stem.
  • For the 2016 Sweet Pea Trial, the best sowing times were the 13th February 2016 and the 12th March 2016.  The 26th October 2015 sowings didn’t do so well, possibly because of the prolonged periods of inclement weather these earlier sown seedlings endured.
  • Ambient temperature did not appear to significantly affect the stem lengths of sweet peas, nor the number of flowers produced. 
  • One of the biggest factors affecting the quality of the plants, the number of flowers produced, and the overall success of sweet peas, is the arrival of the insectivorous insects and animals.  If the aphid predators arrive late, it has a significant effect on the overall success of the Sweet Pea harvest.

I am hopeful that 2017 will be an even better year to grow Sweet Peas, I am already looking forward to my 2017 Sweet Pea Trial!

Further Trials

You may be interested in some of the other trials I have conducted.

Sweet Pea Trial Reports

To read the results of my 2017 Sweet Pea Trial, please click here.

To read the results of my 2015 Sweet Pea Trial, please click here.

Compost Trial Reports

To read the results of my 2017 Compost Trial Report: Growing Carrots, please click here.

To read the results of my 2017 Compost Trial Report: Growing Broad Beans, please click here.

To read the results of my 2016 Compost Trial Report: Growing French Beans , please click here.

To read advice on planting up containers, please click here.

Scented Daffodil Trial Reports

To read the results of my 2017 Scented Daffodil Trial, please click here.

Terrarium, Vivarium, and Orchidarium Trials

To see how my Orchidarium was created, please click here.

To read the first part of my White Orchid BiOrbAir Terrarium Trial, please click here.

To read the first part of my Madagascar BiOrbAir Terrarium Trial, please click here.

To read the first part of my Miniature Orchid BiOrbAir Terrarium Trial, please click here.

To read about the general care I give to my orchids and terrarium plants, and the general maintenance I give to my BiOrbAir terrariums, please click here.

To read how I track the temperature, humidity, and light conditions inside my terrariums, please click here.

Other articles and links that may interest you……

I sowed all of my Sweet Pea seeds in Dalefoot Composts’ Wool Potting Compost, and I enriched the soil where the Sweet Pea plants were planted, with Dalefoot Composts’ Double Strength Wool Compost for my 2016 Sweet Pea Trial.  To visit Dalefoot Composts’ website, please click here.

I sowed all of my Sweet Pea seeds in Deep Rootrainers for both my 2015 and 2016 Sweet Pea Trials.  To visit Haxnicks’ website, where you can find out more information about Deep Rootrainers, please click here.

I used the Rootrainers Racking Station for my 2015 and 2016 Sweet Pea Trials.  To visit Haxnicks’ website, where you can find out more information about the Rootrainers Racking Station, please click here.

I purchased my seeds for my 2015 and 2016 Sweet Pea Trials, from Roger Parsons Sweet Peas, to visit Roger Parsons’ website, please click here.

I am a member of the National Sweet Pea Society.  If you’d like to visit the National Sweet Pea Society’s website, where you can find out more about this charity and learn more about Sweet Peas, please click here.

For gardening advice and lovely tips and ideas of what you could do in your garden, or at your allotment, from mid-October to mid-November, please click here.

For information on terrariums and bottle gardens, please click here.

For gardening advice and lovely tips and ideas of what you could do in your garden, or at your allotment, from mid-November to mid-December, please click here.

For ideas of beautiful, edible plants to grow in your garden, or at your allotment, please click here.

Other articles you might like:

2 thoughts on “Sweet Pea Trial 2016

  1. Good morning – I was so relieved to read in the Vantage Point Magazine that you had also had a poor Sweet Pea year!! Mine were also incredibly disappointing but I am now off to buy some of your recommendations and will get sowing this week for next year’s hopefully amazing display! Thank you

    1. Hello Louisa, thank you for your comment, I am wishing you every success with your Sweet Peas. I am certain that 2017 is going to be a much better year for Sweet Peas – good luck!

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