How to grow sweet peas

Are you wondering how to grow sweet peas? We’re here to help. 

There’s nothing like burying one’s face into a freshly picked bunch. With a heady scent, frilly blooms and wide variety of colours, they make a brilliant cut flower. A stalwart of the cottage garden, they also look fantastic left to ramble up obelisks bringing height, color and fragrance to borders.

See: Flower bed ideas – beautiful ways to create floral displays in your garden

‘I like growing sweet peas up wigwams or tripods, because you can then put them in the border and they rise up and you get the colour working in with the plants around them,’ says the celebrity gardener Monty Don in Gardener’s World (opens in new tab). 

Alternatively, if you don’t have a large garden, then sweet peas can easily be grown in deep containers on a patio or balcony provided they have vertical support.

What is the best way to grow sweet peas?

Sweet peas are easy to grow from seed and can be sown any time from October to March. Sweet peas are hardy annuals and only need protecting from harsh frosts; sowing them in October or November will give them an early start and a chance to establish really strong root growth before being planted out in spring. 

'By sowing sweet peas in October-November you will have bigger plants with a stronger root system that should give flowers next spring earlier and last longer,’ reveals Monty Don in his monthly blog (opens in new tab). 

Another key thing to remember when growing sweet peas, is that they are hungry and thirsty plants, so it is important to fertilize the soil and to keep them well watered, around once a week. ‘Make sure you add lots of organic matter, if nothing else to act as a reservoir to hold moisture for them,’ advises Monty Don.

How to grow sweet peas

If you’re wondering how to grow sweet peas then here’s our step-by-step guide:

1. To encourage strong and vigorous root growth sweet peas are best sown into root trainers or 3 inch pots filled with a mixture of potting compost and 20 per cent sand. Plant a single seed about 1cm deep into each cavity, cover with compost and water. To assist germination, place them in a greenhouse or on a sunny windowsill.

2. Sweet peas are hardy, so once the seedlings have sprouted the sweet peas can be moved outside into a cold frame or a sheltered area of the garden to get maximum sunlight.

3. Once the seedlings have developed two pairs of leaves, pinch out the growing shoot just above the top pair to encourage more vigorous side shoots.

4. Before the seedlings are ready to be planted out in spring, it’s important to prepare your site. Sweet peas are hungry plants, so fertilize the soil by digging in plenty of well rotted manure or organic matter. At this stage you can also prepare your supporting structure. Sweet peas are climbing plants and are best grown up a vertical support such as an obelisk, wigwam or jute netting. 

6. In late March to April, the plants are ready to be planted out. Plant a seedling at the base of each bamboo cane or obelisk support by digging a hole deep enough to accommodate the long roots, infilling with soil and watering in well. Planting in a cluster of three will create a more rambling look.

7. After a couple of weeks, once the plants have established and developed secondary shoots, select the strongest shoot and remove the others, this will encourage a stronger plant and larger blooms.

To keep sweet peas flowering throughout summer it is important not to let them set seed. Pick the flowers to encourage more blooms or dead head as soon as blooms begin to go over.

What month do you plant sweet peas?

You can plant sweet peas from October to March. Sweet peas are hardy annuals so planting them in October or November will give them a head start and a chance to establish really strong root growth before being planted out in spring. 

Planting one batch in October-November, and another in January-February, will help give a continuous supply from May to August.

Do sweet peas need to climb?

Yes, all sweet peas are climbing plants and are best grown up a vertical supporting structure such as an obelisk, wigwam or jute netting. If you are growing sweet peas as a cut flower then they can also be cordon grown up individual canes set in a row as part of a purpose built structure.

See: Vertical garden ideas – plant upwards with tall flowers and create beautiful living walls

How much sun do sweet peas need?

Sweet peas need a good amount of sunlight, but grow best in cooler conditions in moist, free-draining soil and do not like getting too hot. ‘Don’t put them in a blazing sunny position and above all make sure they don’t get dry,’ reveals the celebrity gardener Monty Don on Gardener’s World (opens in new tab). ‘They will need watering once a week unless it is very wet.’