Cosmos bipinnatus. Purity cosmos seeds yield single snow-white flowers to lighten the dark areas of a cottage garden. Regular dead heading will encourage continuous flowering from summer into late autumn. The ferny foliage on this variety is graced by the flowers up to 10cm (4″) in diameter on plants that grow to about 76cm (30″) tall. Stake this variety if growing in exposed areas, or use Green Garden Netting to keep plants upright. When they are just two feet tall, let their tips grow through a layer of netting lain flat over the bed. This will give them all the support they need.