Water requirement: Tolerates drought
Tolerant of most soil pH levels, but grow best in neutral to alkaline soils.
Sow seeds directly in soil after the threat of frost has ended. Young plants may be transplanted from pots at this time. Rich soil will encourage foliage rather than blooms, so it is not necessary to make any special soil preparations.
Sow seeds indoors 4 to 6 weeks before the last frost date in pots with good seed-starting mixture. As soon as they’re 3 or 4 inches tall. move them into bigger pots. As cosmos can be invasive, growing them in pots in some areas is recommended.
Cosmos grow easily in beds, and they make great cut flowers. When established, the plants can handle drought, poor soil conditions, and general neglect. They even self-sow. May reseed, for a surprise return next season, if dried flower heads are left intact.
1-3 feet wide, up to 6 feet tall.
Susceptible to stem canker, powdery mildew, aphids, flea beetles or gray mould. These are easy to control with insecticidal soap, or by spacing plants accordingly to ensure quality air flow.
Spread: Up to 6 feet, 1-3 feet wide.
Remove spent blooms to prolong flowering.