The 2027 garden calendar is here · Find your calendar
garden
edition
Bag (0)
All plants

Cosmos bipinnatus

Cosmos

Airy, open flowers offer pollen and nectar beside vegetable beds and supply stems for the vase.

Grows in Zones 4–12Growing guide
Cosmos growing or ready to harvestPhoto: Hope Duckworth · CC BY 4.0

Set your expectations

When will it bloom?

Usually 8–12 weeks from seed to first flowers
Cold-weather noteWait until frost danger passes before planting outdoors.
Start withSeeds or nursery transplants
Life cycleWarm-season annual
DifficultyEasy to moderate

Your seasonal plan

When to grow cosmos in Zone 6.

The flower row shows when established plants may bloom. Leave some flowers for insects and adjust planting to your local frost dates. These are useful planning windows, not exact weather guarantees.

Typical planting windowMay–June
Typical bloom windowJune–September

Growing essentials

What cosmos need to thrive.

Use the practical details below with your Zone 6 timeline. Current weather and the variety you choose can shift timing.

LightFull sun
SoilAverage, well-drained soil with modest fertility
Planting depthSow about ¼ inch deep; do not bury deeply.
Spacing12–18 inches apart; allow more for tall varieties
WaterKeep the seedbed moist until seedlings emerge; water established plants during dry spells.
Best conditionsMatch planting to local frost dates; mature hardiness and summer heat tolerance vary.

How to plant

Plant it well.

Sow after frost when soil has warmed to about 65°F. Put tall varieties on a bed edge where they will not shade vegetables.

Indoors or containers

Start a few weeks before the last frost or sow outdoors; mature plants need outdoor light.

Keep it growing

Care through the season.

  • Stake tall plants in windy gardens. Remove spent blooms to extend flowering, and leave some seed heads for birds.
What to avoid

Rich feeding that produces leafy growth at the expense of flowers.

Ready to harvest

Know the cue, not just the date.

  • Cut stems as flowers begin to open, leaving some blooms for insects. This guide recommends cosmos for flowers rather than eating.

How we know

Sources and growing guidance.

The growing essentials and seasonal planning windows are original summaries informed by university Extension references; always adjust for current local weather and variety instructions.

Cosmos: plant profile and cultivationNorth Carolina State ExtensionFlowers in the vegetable gardenUniversity of Illinois Extension

Extension sources checked · November 2026. Seasonal windows are planning estimates.