Although many gardeners sow sweet pea in spring, it may also be sown during the next month or so, leaving time for other urgent tasks next year. Plants started now may bloom earlier, and will be sturdier, having made harder, slower growth. You can soften the outer coating of the seeds by grazing them with sandpaper and soaking overnight in lukewarm water.
Sow the seeds one to two centimetres deep in pots of compost - about five seeds to a 1.5 litre pot. In mild areas the pots can be left outside or in a cold frame. In colder regions, you may need to bring them into an unheated greenhouse during frosty spells. Do not keep indoors or in a heated greenhouse, as the plants will make too much soft growth. When the plants are about 10 centimetres tall, nip out the growing tips so that they become more bushy.