Cosmos are an annual, semi-hardy herb up to 2 m tall with bright orange or yellow flowers generally used as an ornamental. Cosmos are also effective nectaries for butterflies, and can be planted to attract pollinators and other beneficial insects such as syrphid flies, lacewings, and parasitic wasps.
Cosmos flowers are effective nectaries for butterflies and can be grown to attract pollinators and other beneficial insects such as syrphid flies, lacewings and parasitic wasps (Allen, 2009). Cosmos are also said to repel the corn earworm, Helicoverpa zea (Cornell, 2013).
Cosmos flowers are used as a yellow/gold dye in traditional textile production in Southern Africa and the Americas.
Plant in well-drained soil in full sun to partial shade. Seeds can be covered with 0.6cm of soil since they do not need light to germinate. Germination will usually occur in just 3 to 5 days, but it can take up to 2 weeks.
Cosmos may require staking when grown. Remove dead flowers to prolong flowering period.
Known environmental conditions for production – Cosmos is highly adaptable to a wide variety of conditions, particularly in warm climates.
Known soil requirements – Cosmos requires well-drained soil. It is tolerant of low fertility, but will become leggy if soil is too rich. It prefers neutral to alkaline pH.
Harvesting and Seed Production
Once flowers have been dried, long spiny seeds become visible clinging to the brown remains of the flower head. These can be removed and laid out to dry further before storage.
Pests and Diseases
Cosmos may be attacked by aphids, thrips or Lygus spp. plant bugs. Cosmos is susceptible to aster yellows, a pathogen which causes flower parts to develop into malformed leafy structures. It is also susceptible to powdery mildew, beet curly top virus and tomato spotted wilt virus