Growing Sweet Peas From Seed – My Full Guide

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Growing sweet peas from seed rather than buying them as already grown plants is definitely a much cheaper way of growing sweet peas. But if you are growing sweet peas from seed for the first time then this guide is for you. It will comprehensively guide you through all the steps of growing sweet peas from seed to bloom.

How to sow sweet peas

I recently ran an experiment to find out the best way to sow sweet peas. From my results soaking them for 24-48 hours and then growing them in a heated seed tray worked the best. If you have a root trainer that you can put on a heated seed mat this will be the best option.

A root trainer is better for sweet peas than a regular cell tray as they grow a large tap root. The root trainer leaves plenty of room for this to grow and then easily opens from the side for a damage free transplant.

Heated Seed Mat
From My Sweet Pea Sowing Experiment

When to plant out sweet peas

You want to plant out your sweet peas once the last frost has passed. For most of us UK-based gardeners that normally means sometime in May.

This will obviously vary based on whereabouts in the country you are. Where I am, up in the Pennine hills, the risk of frost lasts until later in the year than it would for gardeners further south.

The risk is not always that the frost will kill the sweet peas, they are reasonably hardy, the problem is that the cold weather will really stunt the growth of sweet peas. A small seedling sitting just above the surface of the soil not growing is just a target for slugs and will get eaten down to a stump.

Mixed colours of sweet pea flowers
Mixed colours of sweet pea flowers

When were they sown?

How old the seedlings are can also affect when you can plant them out. Larger peas that were sown the previous autumn will be a lot hardier than fresh spring seedlings and as such you can move these out into the garden earlier. As I said before sweet peas are fairly hardy, but you want them to be growing once they are planted out to help with attacks from slugs and other pests.

Hardening Off

as with most seedlings started inside in warmer conditions you will want to harden your sweet peas off before you plant them. The hardening-off process involves moving the sweet peas outside in pots for gradually longer periods of time. Start them off with a few hours during the day before lengthening the amount of time they stay outdoors. Do this over the course of 2-3 weeks.

How to support Sweet Peas

There are lots of different ways you can support sweet peas, so many that it may feel overwhelming. but don’t worry, it is simple enough, just give them something to grow up. Anything will work as long as it is strong enough to support the peas. For more info check out my how to support sweet peas article.


Probably the first thing that pops into your head when you think of sweet pea supports, the classic wigwam. A staple of British cottage gardens, sweet peas just look so right growing up a homemade wigwam.

Sweet Peas Growing up a Hazel Wigwam
Sweet Peas Growing up a Hazel Wigwam


I must admit this is something I have never done, but after seeing this display below it is something I must definitely try.

Sweet Peas in Archway
Sweet Peas in Archway


A wooden garden trellis provides ideal support for sweet peas to flourish on. All the different holes give plenty of places for the plants to attach to ensuring they are well supported.

Sweet Peas Growing On A Trellis
Sweet Peas Growing On A Trellis

Bamboo Canes

An allotment favourite, a row of bamboo canes. Ideal for holding up sweet peas and makes a lot of sense if you are growing sweet peas on your allotment to be used as cut flowers.

Sweet Peas Growing Up Bamboo Canes
Sweet Peas Growing Up Bamboo Canes


Sweet peas will love to climb up any kind of netting. Here in the photo, they are growing up chicken wire but this could just as easily be square metal or even plastic netting.

Sweet Peas Growing on Chicken Wire
Sweet Peas Growing on Chicken Wire

Sweetpea FAQ’s

Are sweet peas perennial?

No sweet peas are an annual plant, they will not come back year after year.

Can you eat sweetpeas?

No, sweet peas are grown purely for their looks. Unlike many other legumes, they are actually toxic to humans if consumed.

Are sweet peas poisonous to pets?

Yes, as they are poisonous to humans they are also poisonous to pets, so make sure you keep an eye on your pets when they are hovering around sweet peas.

How high can sweet peas grow?

With the proper support, sweet peas can grow to 2m or even slightly above!

When do you grow sweet peas?

The traditional season for sweet peas is June and July but with the right care and attention, they can be both started earlier and grown later into the season. Regular deadheading of sweetpeas can massively prolong their flowering period.

How to germinate sweet peas?

I like to soak my sweet pea seeds in water for 24 hours before planting them in a seed tray. This soaking helps to break down the tough shell around the seed allowing them to germinate better.

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  1. There are perennial sweet peas, but they don’t smell of anything, so are a bit useless really.

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