Sowing Sow the seeds thinly in a well prepared seed bed 2cm (1”) deep in rows 15-20cm (4-8”) apart. Planting Thin the seedlings as they grow to 10cm (4”) apart. When the plants are about 15cm (6”) tall, plant out in the growing site 60cm (24”) apart. Firm in the plants well. Other Instructions All brassica are susceptible to caterpillar attack. Keep an eye out as they have voracious appetites.