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Cosmos
Cosmos bipinnatus
Cosmos blooms from June through October.
Mature size, hardiness zones, sun and the trait tags were checked against named botanical sources for this plant. The bloom months and water need on this page were not.
Growing Cosmos
Plant it in full sun. It prefers low water. Expect it to reach about 3.3 ft tall and 1.3 ft wide at maturity, in roughly 1 year.
When to plant Cosmos
Wait until all danger of frost has passed, then plant out Cosmos into warm soil; in most zones that means late spring. Planted then, it flowers from June to October.
Month-by-month timing for your zone is on the planting calendar.
Comes in 11 varieties across 5 colors
Same plant, same care - pick the color you are growing.
Good to know about Cosmos
Curated from university extensions, botanic gardens and other primary sources, with the source named on every note.
Worth knowing
It thrives on neglect. Rich soil and feeding give lush leaves with few flowers, so plant it in poor, lean ground and skip the fertilizer for the best bloom. per NC State and Illinois
Height depends on cultivar
Sources range from about 12 to 24 in on compact types up to 6 ft on tall garden strains. Rich soil pushes plants taller. Buy by named cultivar height. per NC State and Illinois
Self-sows into next year
A frost-killed annual, but dropped seed sprouts the next season, so a planting returns as volunteers. It appears on the US Invasive Plant Atlas, so reseeding can turn weedy. per NC State
A magnet for pollinators
The open, single daisy flowers attract bees and butterflies, and the seed heads draw birds. A classic bee-and-butterfly annual. per NC State and Illinois
Cut it for more bloom
Deadheading keeps it flowering, and cutting for bouquets does the same. Shear leggy plants back to 30 to 45 cm (12 to 18 in) for a fresh flush. per NC State
Not orange or chocolate cosmos
Garden cosmos is the pink, white, and crimson type. Not sulfur cosmos (gold-to-orange Cosmos sulphureus) or chocolate cosmos (tuberous Cosmos atrosanguineus). Match the species to the color you want. per NC State
What pairs well with Cosmos
Good companions share its growing conditions and add something it lacks: an earlier or later bloom, a lower carpet in front, or structure through winter.
Rock Cress
Shares full sun and low water; blooms in mid spring, before this one opens; low at 4 in, to carpet the ground beneath; both offer pollinator forage, in different months.
Sea Thrift
Shares full sun and low water; opens in mid spring and overlaps into this one's season; lower at 8 in, for the front of the border; evergreen, so the bed keeps its shape through winter.
Creeping Phlox
Shares full sun and low water; blooms in mid spring, before this one opens; low at 6 in, to carpet the ground beneath; both are strong pollinator plants, and they feed in different months.
Thyme
Shares full sun and low water; opens in late spring and overlaps into this one's season; low at 6 in, to carpet the ground beneath; both are strong pollinator plants.
Crocus
Shares full sun and low water; blooms in late winter, before this one opens; low at 4 in, to carpet the ground beneath; both offer pollinator forage, in different months.
Grape Hyacinth
Shares full sun and low water; blooms in early spring, before this one opens; lower at 8 in, for the front of the border; both offer pollinator forage, in different months.
Rosemary
Shares full sun and low water; blooms in early spring, before this one opens; both are strong pollinator plants, and they feed in different months; evergreen, so the bed keeps its shape through winter.
Flowering Crabapple
Shares full sun and low to moderate water; blooms in mid spring, before this one opens; both are strong pollinator plants, and they feed in different months; taller at 20 ft, for the layer behind it.
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