Sweet peas can be sown from November until March under cover. Soak your seeds overnight in tepid water, sow four seeds in a 9cm pot, and keep them under cover to be planted out in Spring. You can also direct sow them into the ground in April or May, but they will need protection from slugs and snails.
Plant out your seedlings once the risk of frost has passed. It’s best to harden off young plants for 3-5 days to acclimatise; you can do this by covering them with fleece overnight once planted or by leaving the modules outside during the day. Make sure you have good supports, around 1.5-2 metres, for your sweet peas to clamber up. Plant them out at 25 x 25 cm spacing.
Sweet peas can be pinched out at around 10 cm to encourage bushy growth (although it’s not essential). Give them a little water during dry spells and help guide them back towards the supports you built. Other than that, keep picking the flowers, and they will keep coming.
Sweet peas need protection against slugs and snails when young. Check regularly for aphids. Ensure there is enough airflow to reduce the risk of downy mildew.
Sweet peas will start to flower in early summer and will continue throughout the season if you keep picking the blooms. The stems will get shorter as the plants age. Use secateurs, as the stems are fibrous and don’t snap off easily. Once the plant starts making seeds, it will stop producing as many flowers. If you want more blooms, remove all seed pods and deadhead regularly.
Do not eat sweet peas; they are toxic. The seed pods look like tiny pea pods, so it would be easy to think they are edible, but they contain Aminopronprionitrile, which is toxic to consume.
Select the best plants and do not harvest flowers or deadhead from them; slim pods will form and start to dry on the plant. If you leave the plant in situ, these pods will crack open in spirals and shed their seeds in situ. Collect the seeds once the pods are dry, brittle, and brown. Spread them out for a week in a cool, dry place and store them for up to 4 years.