Growing sweet peas, Lathyrus odoratus, for summer fragrance

Growing sweet peas, Lathyrus odoratus, for summer fragrance

Gardening blog by Debby Lockey Garden Design

When to plant your seeds

sweet peasWe are already into March and I’ve realised that I haven’t sown my sweet peas.  I usually try to sow the seeds during the winter months as I feel these cold tough conditions produce a more robust healthy plant. However it is not too late. This article will guide you through the process of growing your own sweet peas from seed. 

Sweet peas can be sown undercover in cold greenhouses or cold frames from mid October to March, but if you find you have missed this window of opportunity the seeds can be grown directly into the ground from April onwards.  If you are planning to do this be aware that mice love to eat them.  One way to deter these little creatures is to soak the seeds in paraffin before planting them as this makes them unpalatable to mice (the same applies to edible pea seeds grown in the vegetable garden).  Alternatively you can use mouse traps.

Seed germination

There are several suggestions to help you get your sweet peas to germinate.  Putting the seeds in the freezer overnight, or nicking the seed coat on the opposite side to the eye of the seed (the small round scar on the seed) with a penknife before planting is supposed to help.  The former makes the seeds think winter has been and gone so it’s time to germinate, while the latter allows water into the seed, and so encourages germination.  Due to lack of time or inclination, I don’t do either of the above, but I do soak them overnight, as this is supposed to encourage the seed embryo to swell and put out roots and shoots.   Generally I have good results doing this, but remember not to soak them for too long as they will rot.

sweet pea scented Which pots to grow them in

Again there are those who say that the seeds should be planted into loo rolls or containers made from rolled up newspaper.  The thinking behind this is that sweet peas like long root runs so using deep pots will allow encourage this. I have tried both these methods but I actually found that the paper/ cardboard didn’t rot down, consequently the roots didn’t spread out and become strong, so the plants were rather spindly.   I now prefer to sow 3 seeds into ordinary pots 3 inches across the top, using seeding compost.  The pots can be plastic, pottery or metal; it doesn’t seem to make much difference. Push the seeds down into the compost so they are about a ½ an inch to an inch below the surface.  Cover with more compost.

Germination period

sweet peas germinationThe seeds can take between 10 – 28 days to germinate. Once the shoots begin to appear I like to keep an eye on them and turn the pots if it looks as if the plants are leaning too far towards the light.

Pinching out

Because I have left planting till quite late I will probably have to pinch out the top shoots.  This practice of removing the top 2 leaves of the seedlings once 3-4 pairs of leaves have appeared, is recommended as it encourages strong, bushy side shoots which is where the flowers will grow.   If I had sown my seeds in autumn, the frost would have naturally killed this top shoot off so I wouldn’t have needed to do this job.

Suitable site for growing your sweet peas

I’ll keep the sweet pea shoots in their pots, under glass until the frost has passed and the soil has begun to warm up.  During this time I’ll choose a sunny site for the sweet peas and prepare the soil so it will be ready for when the shoots need to be planted out.  My soil has quite a high clay content so I’ll put in some well rotted manure and home made compost to ensure drainage is good and there is food available for these hungry plants. If you have sandy soil put some torn up newspaper at the bottom of a trench to help retain the moisture, then add the manure.   As sweet peas need support I’ll also put an obelisk in position.

Planting out

Before planting the shoots out they have to be hardened off. This is simply taking them out of the cloches during the day but covering them at night.  Do this for around 2 – 3 weeks so the plants can get used to cooler temperatures, the movement of air around them and lower humidity.  This can be started around April / May time depending on the spring we have. You don’t want them to be caught out by a late frost which could kill them.

sweet pea scentedAftercare

Sweet peas do need care once they have been planted out.  If you are gardening on poor soil feed them with a general fertilizer every 2 weeks such as a potash rich tomato feed.  Also keep water them when the weather is dry otherwise they won’t flower as well.  Water in the morning so the leaves don’t get scorched and the plant doesn’t succumb to bud drop.

Keep tying the shoots in as they grow.  If you don’t they have a tendency to flop, with the result that the flower stems are short and curly rather than long and straight.

Once the plant starts to flower it is important that you pick them on a daily basis, otherwise the energy of the plant goes into producing seeds rather than more flowers.  Eventually a point will be reached where the flower stalks will get shorter and you know that the plant is coming to the end of its life.

Flower arrangements

But up until that point you’ll have an abundance of flowers to fill your house with scent.  They can be put in a vase on their own or added to cornflowers and roses for a relaxed, traditional cottage garden arrangement.  If you are getting married this year think about having them in your bouquet.  Local florist Finola Shaw finds she has lot of requests for fresh, local handpicked flowers in her wedding bouquets.  

Good luck.  I believe a little bit of time and effort now will really pay off in the summer months when you are rewarded with handfuls of sweet peas!


For more gardening information and advice, contact Debby Lockey Garden Design. 


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