I love Sweet Peas. Every year I look forward to being charmed by the Sweet Pea’s beautiful flowers and romanced by their heavenly fragrance. Sweet Peas are certainly an annual that I recommend you try growing. Sweet Peas, which are also known by their botanical name of Lathyrus odoratus, are very versatile, here in the UK, you can sow their seeds from September right through until April. So there’s absolutely no reason not to try growing this pretty annual, you have plenty of time!
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 best time to sow your Sweet Pea seeds, I hope that this article with the results of my 2015 Sweet Pea Trial, will help you.
Sweet Pea Trial
For my trial I decided to sow the same varieties of Sweet Pea seeds, all of which were purchased from the same company, and grown in the same conditions, the seeds were sown at the same time every month, from September 2014 through until March 2015. This allowed me to compare the number of flowers, the length of the stem produced, and evaluate if there was a better time of year to sow Sweet Peas for a greater harvest of flowers, or for a longer length of stem.
Sweet Pea cultivars
I purchased all of the Sweet Pea seeds I sowed for this trial from Roger Parson’s Sweet Peas, the varieties I chose are:
- Lathyrus odoratus ‘Earl Grey’
- Lathyrus odoratus ‘Frances Kate’
- Lathyrus odoratus ‘Gwendoline’
- Lathyrus odoratus ‘Judith Wilkinson’
- Lathyrus odoratus ‘Just Julia’
- Lathyrus odoratus ‘Naomi Nazareth’
- Lathyrus odoratus ‘Pip’s Cornish Cream’
- Lathyrus odoratus ‘Susan Burgess’
I started my Sweet Pea trial on Friday 26th September 2014, using one pack of Deep Rootrainers, I sowed the eight different varieties of Spencer type Sweet Peas mentioned above. All of the Sweet Pea seeds were steeped in liquid paraffin for a few moments to deter mice, prior to sowing in Deep Rootrainers, which were filled with New Horizon Organic and Peat Free Multi-Purpose Compost. The tray of Rootrainers was then placed onto the top shelf of a Rootrainers Racking Station, which had triple consecutive strips of copper tape wrapped around its legs for slug protection. The racking system was positioned outside, the Sweet Pea seedlings received no protection whatsoever over the winter months.
I sowed four seeds of each of the aforementioned varieties, into each row of Rootrainers, and labelled each of the Rootrainers compartments with the date of sowing and the variety name. I intended to be able to monitor the conditions and water my Sweet Pea seedlings when they required it, but the reality was that the seedlings didn’t always receive water when they should have done, and were consequently grown in quite harsh conditions, with all of the plants experiencing repeated periods of drought. The seedlings did all experience the same equally harsh conditions though!
I also intended to be able to feed my Sweet Pea plants more often than I was able to in reality, again the plants all received the same amount of fertiliser, and were all grown in the same growing media.
I sowed another tray of Rootrainers next month and every month from September 2014 until March 2015.
Sweet Pea Sowing Dates
My sowing dates were as follows:
- 26th September 2014
- 26th October 2014
- 26th November 2014
- 26th December 2014
- 26th January 2015
- 26th February 2015
- 26th March 2015
Sweet Pea Wigwams
The Sweet Pea plants in this trial were all planted out at the same time, and were grown in a rather wild, natural way – none of the Sweet Pea plants had any of their tendrils removed, and none of the plants were tied to their supports. The Sweet Pea plants were grown up a series of home-made wigwams. All of the Sweet Pea plants were self supporting and required no further tying in or support.
Sweet Pea Pests
I didn’t apply any preventative sprays or deterrents for pests, and I didn’t spray my plants at all, even when pests arrived.
As you can see in the photograph below, my 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!), feeding through the Sweet Pea plant’s leaves, stems and flowers. The resulting damage and nutrient loss weakens plants, resulting in distortion and stunted growth.
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 quickly form, hampering the plant’s ability to photosynthesise.
With no preventative sprays my Sweet Pea plants relied on the protection of beneficial insects to control the aphid infestations – ladybirds, a natural predator of aphids, ladybird larvae who also feed on aphids, and hoverflies, whose larvae feed on aphids, were frequently seen on the plants, as were a variety of different garden birds, including long-tailed tits and blue tits. These natural predators soon had the aphids under control.
The aphids were not noticeably more prevalent on any of the Sweet Pea plants, and neither were they absent on any of the plants. The aphids were, as expected, very evenly, and efficiently spread throughout the plants, no matter as to the plant’s date of their sowing.
Slugs and snails
Other than the copper tape, of which I used three strips of in succession for each leg of my Rootrainers Racking Station, I provided no other deterrents for slugs or snails. I did see a number of snails and slugs during the course of the trial, but they caused very little noticeable damage to my plants. I was happy to let these little creatures eat some of the leaves from my Sweet Pea plants and did not attempt to remove them. 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.
Sweet Pea Trial 2015 Results
I picked my first Sweet Pea flower, Lathyrus odoratus ‘Naomi Nazareth’, on 28th May 2015. I ended my trial on 25th September 2015, when I picked 8 Lathyrus odoratus ‘Naomi Nazareth’ flowers, 5 Lathyrus odoratus ‘Just Julia’ flowers, 5 Lathyrus odoratus ‘Gwendoline’ flowers, 9 Lathyrus odoratus ‘Susan Burgess’ flowers, and 4 Lathyrus odoratus ‘Earl Grey’ flowers. The Sweet Pea flowers were picked, recorded and their stem lengths measured once each day for the duration of the trial. I stopped collecting data for my trial on 25th September 2015, although I should mention that some of my Sweet Pea plants are continuing to flower now, at the beginning of October 2015.
Some interesting facts and figures from the trial:
- During the course of my trial 3,155 Sweet Pea flowers were picked.
- The most productive day during the trial was on the 10th July 2015, when 88 Sweet Pea flowers were harvested, with an average stem length of 19.8cm.
- The longest length of a Sweet Pea flower stem recorded in my trial was 47cm, this was measured on a Lathyrus odoratus ‘Pip’s Cornish Cream’ flower, which was picked on the 24th June 2015.
- The Sweet Pea plant that produced the longest stem was sown in September 2014.
I’ve produced some charts which show various breakdowns of the data I collected during the trial.
Numbers of Sweet Pea flowers harvested per day
Total number of Sweet Pea flowers harvested
Number of Sweet Pea flowers harvested for each month’s sowing time
Sweet Pea flowering stem lengths by variety
Sweet Pea flowering stem lengths by sowing month
Sweet Pea flowering stem lengths and temperature
Sweet Pea Trial Conclusions
Before making any assertions about the data, it’s important to note that the data volume in this trial is not huge, so some of the apparent conclusions may not be statistically significant. However, we can certainly draw some conclusions on the basis of the data in this small trial:
- Lathyrus odoratus ‘Naomi Nazareth’ and Lathyrus odoratus ‘Pip’s Cornish Cream’ were the most prolific flowering varieties in this trial.
- Lathyrus odoratus ‘Just Julia’ produced the least number of flowers in this trial.
- The best month to sow sweet peas, to get the most flowers, is October.
- The worst month to sow sweet peas – when looking for the maximum number of flowers – is November.
- If you are looking for flowers with the longest stems, October is the worst month to sow, and instead you should sow in mid-winter – January or February.
- The day-to-day weather appears to affect the stem length of flowers, giving longer stems when the temperature is warmer.
- With a planned schedule of succession sowing, it’s possible to pick a large bouquet of sweet peas, every day, from early June until October!
I’ll be starting my next Sweet Pea Trial soon, I will be using Rootrainers again to sow my seeds, and I will again be using seed purchased from Roger Parson’s Sweet Peas. This time however, after seeing some great results during my Peat Free Compost Trials this year, I will be using the Wool Potting Compost from Dalefoot Composts, a wonderful peat free potting compost made from composted bracken and sheep’s wool, which provides excellent water retention and slow release nitrogen. I’ll let you know how I get on next year, I am already looking forward to my 2016 Sweet Pea Trial!
Sweet Pea Trials
To read the results of my 2017 Sweet Pea Trial, please click here.
To read the results of my 2016 Sweet Pea Trial, please click here.
Compost Trial Reports
To see all of my Compost Trials, please click here.
To read advice on planting up containers, please click here.
Scented Daffodil Trial Reports
To see the results of my 2018 Scented Daffodil Trial, please click here.
To read the results of my 2018 Scented Daffodil Container Trial, please click here.
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 see the design of my Rainforest Terrarium, 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 see a planting list of ferns, orchids, and other plants that are perfectly suited to growing inside terrariums and bottle gardens, 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.
To read about my Trial of New Tomato Varieties, please click here.
To see all of my Vegetable Trials, please click here.
Other articles and links that may interest you……….
To read about the Queen of Orchids, the largest Orchid species in the world, which flowered at The Royal Botanic Gardens, Kew, please click here.
To read about terrariums and bottle gardens, please click here.
To read about the 20 shortlisted plants, including the finalists and winner of the RHS Chelsea Flower Show Plant Of The Year 2015, a special competition to find the most innovative new plant launched at the RHS Chelsea Flower Show, please click here.
To read about the new lives of some of the Show Gardens from the 2015 RHS Chelsea Flower Show, please click here.
To read about some of the Gold Medal winning nurseries at the 2015 RHS Hampton Court Palace Flower Show, please click here.
To read about growing mushrooms indoors, please click here.