When can I plant out sweet peas?

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Sweet peas can produce amazing displays when grown correctly. part of growing these annual plants correctly is planting them out at the right time. Too early and the cold weather may stunt their growth or even kill them off entirely, on the other hand, if you are too late they may not have enough time to grow to full size.

So what is the right time to plant out your sweet peas, well as all things gardening tends to, the answer depends. It depends on your location, the particular weather that year, where the plants are to be planted and also very importantly, when the sweet peas were sown.

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

Missing the last frost

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.


You will want to grow your sweet peas up a good support structure. Bamboo and willow canes are always popular, but why not check out our supporting sweet peas article for some other ideas.

Sweet Peas in Archway
Sweet Peas in Archway


sweet peas, (Lathyrus odoratus) are a flowering plant belonging to the legume family. They are an annual flower that loves to climb and spread, in the right conditions and with the correct support they can grow to 2 and a half meters tall!

Unlike many other legumes which are grown to be eaten, sweet peas are grown for purely aesthetic reasons. There is evidence to suggest that the pea seeds from a sweet pea plant are actually toxic to humans and not fit for consumption even if this was desired.

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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