Sweet peas have a hard seed coat. To aid germination you may find it helpful to leave them on some damp kitchen paper for 24 hours before sowing.
Sow sweet pea seeds undercover between October and April. Rootrainers or loo rolls are ideal as they provide a deep, narrow root run. If you sow into a short, stumpy pot, it doesn’t give the roots as much chance to grow and branch.
To sow the seed, use a peat-free, multi-purpose potting compost and sow two seeds per pot. Dampen the compost, then, with your finger, push each seed in 2-3cm below the surface of the compost. Then label the pot if needed.
If sowing in autumn or spring, sweet peas can be germinated in an unheated greenhouse or cold frame. If sowing in mid-winter, germinate them on a windowsill, heated propagator or very gently heated greenhouse.
Mice love sweet pea seeds and your whole crop may disappear in one go so keep them somewhere mouse-free or try soaking the seeds in liquid seaweed fertiliser before sowing to make them unpalatable.
Check for germination every day and don’t water until you see seedlings start to come through, usually in 10-14 days. Once the seedlings appear, keep them cool at about 5°C (40°F). This promotes root growth, rather than stem growth, which is exactly what you want. An unheated greenhouse or cold frame is usually sufficient.
When there are three or four pairs of leaves, pinch out the leaders – just squeeze off the growing tip between your finger and thumb. This promotes vigorous side shoot formation, with the energy of the plant directed toward growing out, not up.
Check your plants regularly and water them lightly if the surface begins to look dry. About a month from germination, check the bottom of the pot for white roots.
If you sowed your sweet peas in spring, they can be planted directly outdoors during a mild spell in March-May. If you sowed them in autumn or winter, you’ll need to pot the plants up in their pairs. Don’t let them get pot-bound in the rootrainers, they will never be quite the same again. A slim, deep, 1 litre pot is ideal. Use a good compost and water them in. Once the roots have filled that pot, it’s time to plant them outside – do this during a mild spell in March-May.
