You might think it's too soon to be thinking about how to grow sweet peas, but now is a great time to starting planning next year's blooms. Sweet peas fill the summer garden with colour and scent. Beautiful to look at, they should be an essential part of your planting routine. They regularly top the UK’s 'favourite summer flower' polls, thanks to the variety of colours, depth of scent and their versatility. Bring them into the house too and arrange in small pots to enjoy their lingering scent up close.
As well as scrambling up cane wigwams and pergolas, you can also buy varieties that offer low-growing ground cover and there are some varieties that love a hanging basket too. Keep reading for all you need to know about how to grow sweet peas seeds successfully, and why now is a great time to start sowing them. For more advice, see our guide to how to grow flowers from seeds.
How to grow sweet peas
Sweet peas can be sown now, either in the ground or in pots, then overwintered in a greenhouse or cold frame. The resulting plants will have stronger roots than those sown next spring and will flower earlier, too. For the best of both worlds, sow some now and a later batch in spring for a succession of blooms that will last right through summer and into next autumn.
How to sow sweet pea seeds
Sweet peas have deep roots, so sow them singly in Rootrainers (see below) or several in one large, deep pot, using seed compost mixed with multi-purpose. You can soak them overnight or weaken the hard shell of the seed with a nail file before sowing, but they should germinate successfully without this. Overwinter seedlings in a well-ventilated greenhouse or cold frame, and plant out next spring once the soil has started to warm up.
Collecting sweet pea seeds
If you've grown your own sweet peas this year now is the time to save the seeds. Collect the seedpods and bring them indoors. Remove the seeds from the pods and let them dry for a few days on a layer of newspaper. Once dry, store them in an airtight container in a cool place until you want to plant them.
Top tips for growing sweet peas
Rootrainers are deep modules that open out so seedlings can be planted without disturbing their roots. Alternatively, you can use cardboard tubes from toilet and kitchen rolls, which are are ideal for sweet peas as they can be planted whole and will slowly decompose in the soil.
Pinching out sweet pea seedlings as they grow encourages them to develop bushy side shoots that will produce more flowers.
Although they are hardy, once your sweet peas are sown they will need some TLC to make sure they stay healthy, and keep pests and diseases at bay.
1 Stand pots on a layer of gravel in the cold frame to deter slugs and snails.
2 To keep hungry mice away, soak the seeds briefly in liquid paraffin as an effective deterrent.
3 Slugs and snails will be attracted by their tender young growth, so regularly spray seedlings with slug and snail repellent to keep them safe.
4 Too much warmth and not enough light leads to spindly growth. A cool, light place makes for stronger plants.
5 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. Close them at dusk.