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Cosmos
Cosmos bipinnatus
Cosmos blooms from June through October.
Months here are Northern Hemisphere months; in the Southern Hemisphere, shift them by six months.
Growing Cosmos
Plant it in full sun. It prefers low water. Expect it to reach about 3.5 ft tall and 1.5 ft wide at maturity, in roughly 1 year (not yet checked).
No toxicity note is on file for Cosmos. That is not a clearance: check its safety for people and pets before planting.
What was checked
Mature height and spread, 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, and each fact above says which. The planting, spacing and size sections are derived from these checked facts by a fixed rule, not checked separately, and the plant type is the library's own classification.
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. Derived from the plant's category, zones and bloom months plus typical zone frost dates, not checked separately.
How big does Cosmos get?
3.5 fttall5 ft 7 inan adult1.5 ftwideSee Cosmos in a garden plan: the planner shows it in 3D beside everything else you add, growing toward this size over the years.
How far apart to plant Cosmos
Derived from the mature spread above by a fixed rule, not checked separately: spacing is the spread, center to center.
Space Cosmos about 1.5 ft apart, center to center, so each plant has room to reach its full width.
Add Cosmos to a garden plan and the planner draws it at its full width, so you see the spacing before you buy.
Where these facts come from
Cosmos' height, spread, hardiness zones, sun and trait tags were checked against 10 published sources on July 29, 2026. Each one is linked below with every fact it carried, which can include a fact this page still marks as not yet checked, because a source carrying a value is not the same as the value being held to the standard. Facts not in that list, and the planting, spacing and size sections, are not covered by these sources.
- Missouri Botanical GardenPlant Finder, Cosmos bipinnatusheight, spread, hardiness zones, sun and trait tags
- NC State ExtensionGardener Plant Toolbox, Cosmos bipinnatusheight, spread, hardiness zones, sun and trait tags
- American MeadowsCosmos bipinnatus Seedsheight, hardiness zones, sun and trait tags
- Cornell Cooperative ExtensionCornell University Home Gardening, Flower Growing Guide: Cosmosheight, spread, sun and trait tags
- University of Florida IFASExtension, FP149 Cosmos bipinnatusheight, spread, sun and trait tags
- RHSRoyal Horticultural Society, Cosmos bipinnatusheight, spread and sun
- University of Illinois ExtensionHort Answers, Cosmos bipinnatusheight, sun and trait tags
- Utah State University ExtensionYard and Garden: Cosmos in the Gardenheight, sun and trait tags
- Swallowtail Garden SeedsCosmossun and trait tags
- Native Plant Trust (Go Botany)Native Plant Trust Go Botany, Cosmos bipinnatustrait tags
How the checking works, and what each standard covers, is on the verified plants page.
Comes in 11 varieties across 5 colors
Same genus, similar care - pick the color you are growing.
- Apricot Lemonade
- Bright Lights
- Cosmic Red
- Cosmic Yellow
- Dazzler
- Double Click Rose
- Purity
- Rubenza
- Sea Shells
- Sensation Pink
- Xanthos
Compare every variety in the Cosmos group
Every figure is the variety's own page fact. Tap a name to open it.
| Variety | Color | Blooms | Hardiness | Sun | Size (H × W) |
|---|---|---|---|---|---|
| Apricot Lemonade | Yellow | Jun–Oct | Annual (replant yearly) | Full sun | 2.5 ft × 1.5 ft |
| Bright Lights | Orange | Jun–Oct | Annual (replant yearly) | Full sun | 3 ft × 1.5 ft |
| Cosmic Red | Red | Jun–Oct | Annual (replant yearly) | Full sun | 16 in × 16 in |
| Cosmic Yellow | Yellow | Jun–Oct | Annual (replant yearly) | Full sun | 16 in × 16 in |
| Cosmosthis page | Pink | Jun–Oct | Annual (replant yearly) | Full sun | 3.5 ft × 1.5 ft |
| Dazzler | Red | Jun–Oct | Annual (replant yearly) | Full sun | 3.5 ft × 1.5 ft |
| Double Click Rose | Pink | Jun–Oct | Annual (replant yearly) | Full sun | 3.5 ft × 1.5 ft |
| Purity | White | Jun–Oct | Annual (replant yearly) | Full sun | 4 ft × 1.5 ft |
| Rubenza | Red | Jun–Oct | Annual (replant yearly) | Full sun | 2.5 ft × 1.5 ft |
| Sea Shells | Pink | Jun–Oct | Annual (replant yearly) | Full sun | 3.5 ft × 1.5 ft |
| Sensation Pink | Pink | Jun–Oct | Annual (replant yearly) | Full sun | 4 ft × 1.5 ft |
| Xanthos | Yellow | Jun–Oct | Annual (replant yearly) | Full sun | 20 in × 16 in |
Good to know about Cosmos
Curated from university extensions, botanic gardens and other primary sources, with the source named on every note. A note reports what its source says; where that differs from a fact above, the fact above is this entry's stored value, and its mark says whether it has been checked.
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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Design a garden with this
Drop this plant onto a 3D plan, see how it fills in, and watch your whole garden bloom across the year.