How to grow sweet peas: follow our advice for fabulous summer blooms

Find out how to grow sweet peas with our tips – we've got everything you need to know on sowing, planting, and picking

how to grow sweet peas: bundle of flowers in trug
(Image credit: Thompson & Morgan)

Learning how to grow sweet peas is really quite straightforward, but will reward you with some of the most exquisite summer blooms. It's no surprise that they regularly top the UK's 'favourite summer flower' polls, thanks to the variety of colours, incredible scent, and versatility. 

What's more, they make wonderful cut flowers – simply arrange in a vintage jug or glass bottle to brighten your home. And the more you pick, the more they grow!

We've pulled together all the advice you need to get you ready to grow your own sweet peas this year. And once you're feeling inspired, why not head over to our guide on how to grow flowers from seeds too, for even more beautiful blooms?

When is the best time to sow sweet peas?

how to grow sweet peas: bunch of blooms

(Image credit: Jonathan Buckley/Future)

You can sow sweet peas in early spring, either into root trainers or, if the soil is warm enough, straight into the ground. 

You can also sow your sweet peas in autumn, and then overwinter them in a greenhouse or cold frame which will protect them from the colder weather. The resulting plants often have stronger roots than those sown in spring and will flower earlier, too.

However, for the best of both worlds and a succession of blooms that will last right through the warmer months, you can sow some in autumn and a later batch in spring.

How to sow sweet peas in five simple steps

Step one: prepare your seeds

Sweet pea seeds

Soak your seeds to speed up germination

(Image credit: Future)

The experts at Floret suggest to soak your sweet pea seeds in water for 24 hours before sowing. This softens the seed coat, which in turn, speeds up the sprouting process.

Alternatively, Sue Sanderson from Thompson & Morgan says you can leave the seeds on moist kitchen roll until they swell or sprout. Lay the kitchen roll in a sealed container and place it in a warm room, she adds. 

You can also weaken the shell slightly using a nail file, although this is a little more time consuming. If you don't have time to do any of the above, don't worry, your seeds should still germinate successfully, they just might take a little longer to do so.

Step two: sow the seeds into root trainers

Sweet pea seeds

Root trainers are ideal for sweet pea sowing

(Image credit: Future)

Sweet peas have deep roots, so sow them in root trainers. These are deep modules that open out, so seedlings can be planted without their roots being disturbed. Fill them with a mixture of seed and multi-purpose compost, and, as Floret says, allocate two seeds per pot, using your finger to poke them a half-inch into the soil.

Alternatively, you can use cardboard tubes from toilet and kitchen rolls if you're after some budget garden ideas. These are ideal for sweet peas as they can be planted whole and will slowly decompose in the soil over time.

Step three: cover the seeds to speed up germination

Covering pots with a plastic dome lid will increase humidity and speed up germination, says the team at Floret. Place in a cool greenhouse, or in a bright window of your home.

Pop autumn-sown seeds in a well-ventilated greenhouse or cold frame, ready to be planted out next spring, once the soil has started to warm up.

Step four: pinch out the tips

how to grow sweet peas: pinching out seedlings

Pinch the tops of your seedlings out to encourage bushier growth

(Image credit: Future)

Pinching out the tip of sweet pea seedlings as they grow encourages them to develop bushy side shoots that will produce more flowers. 

The team at Floret says to do this when the plants are between 4-6 inches tall. Pinch just above a leaf joint, leaving two or three leaf nodes.

Step five: plant out your seedlings

how to grow sweet peas: climbing up structure

Sweet peas need a sturdy structure to support their vigorous growth

(Image credit: Ken Leslie/Getty Images)

When your seedlings are looking sturdy and the ground is warm outdoors, it's time to get planting. Before you do so, remember that sweet peas are greedy little plants and require lots of feeding to flourish. So, make sure you're planting them into well-prepared soil. A scattering of bone meal, a thick layer of compost or well-rotted manure, and a generous dose of natural fertiliser will do the trick, suggests the experts at Floret. Mix this deeply into the soil.

You'll also want to provide a structure for your sweet peas to climb up – such as an obelisk or trellis. These can make a pretty feature in themselves, and are perfect if you love our cottage garden ideas. Once this is in position, plant the seedlings out in rows around the structure. Sue Sanderson for Thompson & Morgan advises to place two or three seedlings in each hole for a nice, full display,  planting each group about 15cm apart.

Happy sweet peas will grow fast – be sure to keep them in order by tying them to your structure as they grow, using pieces of string. Don't tie too tightly though, else you might damage the stems.

More top tips for growing sweet peas

how to grow sweet peas: seedlings in trays

Get your sweet peas off to a good start with our advice

(Image credit: cjp/Getty Images)
  • After sowing your seeds, stand the trays on a layer of gravel in the cold frame to deter slugs and snails.
  • To keep hungry mice away, soak the seeds briefly in liquid paraffin as an effective deterrent.
  • Slugs and snails will be attracted by their tender young growth, so regularly spray seedlings with slug and snail repellent to keep them safe.There's more advice on how to get rid of slugs in the garden in our guide. 
  • Too much warmth and not enough light leads to spindly growth. Pop your root trainers in a cool, light place for stronger plants.
  • Poor ventilation is a common mistake that leads to fungal problems. When the weather is warm enough, open the greenhouse and cold frame to circulate air around your seedlings. Remember to close them again at dusk.
  • Sweet peas love water, says the team at Floret, and need consistent moisture to thrive. They suggest to set up soaker hoses as soon as you plant them to keep them looking lush. Our best garden sprinklers can come in handy here, too.
  • The team at Floret also advise to feed your sweet peas weekly once they're planted out, using a diluted fish and seaweed emulsion.

What is the best way to pick sweet peas?

how to grow sweet peas: bouquet in vase

A bouquet of sweet peas is a lovely centrepiece for a table

(Image credit: Barbara Rich/Getty Images)

For the longest vase life, pick sweet peas when there are at least two unopened flowers at the tip of a stem, says the team at Floret. Add flower food to the water to extend vase life. 

Don't be shy when it comes to picking your sweet peas to enjoy indoors. Doing so actually encourages the plants to bloom for longer, as it stops them from going to seed. Be sure to keep on top of dead-heading, and remove seed pods as soon as possible too to help with this further, as says Sue Sanderson for Thompson & Morgan.

Looking for more gorgeous summer blooms that make lovely cut flowers? Head over to our guides on how to grow dahlias or how to grow peonies.

How do you collect sweet pea seeds for sowing?

Sweet pea seeds

Once your sweet peas have flowered, collect up the seed pods for next year's blooms

(Image credit: Future)

If you're growing your own sweet peas this year, you might want to have a go at saving the seeds after they've flowered. Here's how to do it:

  1. Collect the seedpods and bring them indoors.
  2. Remove the seeds from the pods and let them dry for a few days on a layer of newspaper.
  3. Once dry, store them in an airtight container in a cool place until you want to plant them.

Where to buy sweet peas

It's easy to buy sweet peas as seeds or ready grown plug plants online or from garden centres. Use our quicklinks below to start shopping, or keep scrolling for some of our favourite varieties. 

Where to buy sweet peas in the UK:

Where to buy sweet peas in the US:

Sweet Pea Seeds - Supersonic from Suttons

Sweet Pea Seeds - Supersonic from Suttons
This is a compact variety that's good for container displays on your patio. Can be planted out in April-May and will flower in June to September. 

Sweet Pea 'King Size Navy Blue' from Thompson & Morgan

Sweet Pea 'King Size Navy Blue' from Thompson & Morgan
With dark navy flowers, this stunning variety will pack a punch in your summer displays. It will grow up to 180cm and spread to 30cm. 

Sweet Pea Seeds - Fire & Ice from Dobies

Sweet Pea Seeds - Fire & Ice from Dobies
This stunning combination has white, purple and pink flowers and a strong fragrance. It also has longer stems so is a good choice for patio container displays. Grows up to 200cm.

Sweet Pea, Sweet Dreams Mix from Burpee

Sweet Pea, Sweet Dreams Mix from Burpee
This is an old-fashioned looking sweet pea with a strong fragrance. Includes a wide range of colors to ensure you can enjoy a striking summer display. The flowers have ruffled, bicolor petals. 

Sarah Wilson has been a lifestyle journalist for many years, writing about gardens since 2015. She's written for, Livingetc, Homes & Gardens, as well as Country Homes & Interiors and Modern Gardens magazines. 

Her own (small urban) garden is a work in progress  - so many ideas, not enough space to cram them in. Hero plants include her ever growing collection of ornamental grasses, black bamboo and ferns, and the perennials like salvias and penstemons that come back reliably year after year. All very restrained though when in fact she'd love to pack her garden with gaudy dahlias and giant cannas, so these are top of her wish list for what to grow next.