How to Grow Cosmos
Annual
Cosmos is a warm-season annual native to Mexico and the southern United States, prized for its daisy-like blooms and airy, ferny foliage. The two most common garden species are Cosmos bipinnatus, with pink, white, and rose flowers, and Cosmos sulphureus, with warm orange, gold, and red tones. US gardeners love it because it is one of the easiest flowers to grow from seed, blooms quickly, and thrives on neglect.
Planting
Cosmos is a tender annual that is killed by frost, so sow seed or set out transplants only after all danger of spring frost has passed and the soil has warmed. Direct-sowing is the simplest method: scatter or space seeds where they are to grow, cover them lightly with about one-quarter inch of soil, and keep the bed evenly moist until seedlings appear in about a week. Choose a spot in full sun, meaning at least six hours of direct light, with average, well-drained soil; rich or heavily amended ground produces leafy plants with few flowers. Thin or space plants roughly 12 to 18 inches apart to give them room and good air movement.
Care
Water young plants regularly to help them establish, then reduce watering once they are growing well, since cosmos is quite drought tolerant and dislikes soggy soil. Avoid feeding; cosmos flowers best in lean soil, and extra nutrients encourage foliage at the expense of blooms. Deadhead spent flowers regularly to keep plants tidy and to extend the blooming season, and pinch young plants once when they are about a foot tall to encourage bushier growth. Tall varieties can flop in wind or rain, so stake them early or plant them where neighboring plants offer support, and pull the plants after the first hard fall frost.
Bloom time
Cosmos begins flowering in early to midsummer, usually within about seven to ten weeks of sowing, and continues nonstop until the first hard frost in autumn.
Garden uses
Cosmos makes an excellent long-stemmed cut flower for bouquets and is a strong draw for bees, butterflies, and other pollinators. It works well in the back or middle of sunny borders, in cottage-style and pollinator gardens, in cutting gardens, and in large containers when compact varieties are chosen.
Tips
For a steady supply of blooms, sow a second batch of seed a few weeks after the first, and let a few late flowers go to seed if you want plants to self-sow for next year. Keep soil on the lean side and resist the urge to overwater or overfeed, since stressed cosmos flowers more freely than pampered plants. Cut flowers in the cool of the morning when buds are just opening for the longest vase life.
General guidance for US gardens. Timing and hardiness vary by region; check your local frost dates and hardiness zone. Page updated Aug 4, 2026.