Plant Profile: Cosmos sulphureus

Klondike Cosmos features vibrant golden-yellow or orange flowers and can reach heights of up to 6 feet. The ‘Cosmic’ series is particularly impressive, producing numerous 2-inch double and semi-double blooms in striking shades of orange, red, and yellow, with plants growing to a height of 12 to 18 inches and exhibiting well-branched growth.

For optimal growth, plant cosmos in an area that receives at least half a day of direct sunlight. Sow the seeds outdoors once the threat of frost has passed and the soil temperature has reached a minimum of 65 degrees. Lightly rake the seeds into loose soil, as planting them too deeply can impede germination. Maintain soil moisture for 5 to 10 days post-seeding, with germination occurring within 7 to 21 days. Cosmos require minimal care to yield a profusion of colorful blooms throughout the summer. Taller varieties may need staking to withstand strong winds and storms.

If spring-planted cosmos develop a significant amount of dried seed, refrain from removing the plants. Instead, promote re-blooming by trimming them back to a height of 12 to 18 inches. This will encourage new blooms within a month, and the cut seeds will fall to the ground, germinating in the warm soil and enhancing both the density of your plant population and the overall display of flowers.

Family: Asteraceae (Compositae)

Quick Identification Tips:
Blooms from summer until frost; thrives in full sun; tolerates dry, porous soils; fast-growing; susceptible to bacterial wilt and canker; pests include aphids and Japanese beetles.

Uses: Ideal as a background bedding plant and for cut flowers. Cosmos will reseed during the growing season and may become invasive.

For further details on Cosmos, please refer to additional resources.