Sow Brussels Sprout seed indoors from February. Alternatively direct sow outdoors from March into a well prepared seedbed, for transplanting to their final positions later on. Sow at a depth of 13mm (1/2″) and distance of 30cm (12″) between rows.
Indoors, sow seed in 7.5cm (3″) pots or trays of free-draining, seed sowing compost and cover with a 6mm (1/4″) layer of vermiculite. Place in a propagator or seal container inside a plastic bag at a temperature of 15C (60F) until germination which takes around 7 days. Once germinated, grow Brussels Sprouts on in cooler conditions until all risk of frost has passed and plants are large enough to be transplanted.
Gradually acclimatise them to outdoor conditions over 7 – 10 days before planting Brussels Sprout plants outdoors in firm, rich fertile, well drained soil in full sun. Prepare the soil in advance in early spring by adding plenty of well rotted farmyard manure to the soil to improve its structure and fertility. Plant brassicas at a distance of 60cm (24″) apart and cover with a protective netting or fleece to prevent attack from birds and insects. Water the plants thoroughly after planting.