Cosmos

Family: Asteraceae Annual flowering plant

Planting Schedule

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Feathery, cloudlike blooms open in a vivid wash of color—silky petals with a crisp, satiny sheen that catches the light from every angle.

Cosmos ‘Cosmos’ forms airy, upright stems topped with long-lasting flowers, offering a delicate crunch of texture in the garden and a graceful presence in arrangements. Grow it for abundant cut-flower color and effortless massing in beds and borders, where its airy foliage makes every planting feel light and luminous.

Light: Full SunMaturity: 60 DaysHabit: Upright

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Cosmos Planting Dates by USDA Zone

Estimated US hardiness-zone windows for sow, transplant, and harvest. Enter a US ZIP above for exact local dates, or open a zone below.

Zone	Start Indoors	Sow / Transplant	Harvest
Zone 1a	Protected Environment Only
Zone 1b	May 11th	Jun 1st	Jul 31st – Aug 1st
Zone 2a	May 4th	May 25th	Jul 24th – Aug 29th
Zone 2b	Apr 24th	May 15th	Jul 14th – Aug 25th
Zone 3a	Apr 24th	May 15th	Jul 14th – Sep 1st
Zone 3b	Apr 28th	May 19th	Jul 18th – Sep 21st
Zone 4a	Apr 24th	May 15th	Jul 14th – Sep 24th
Zone 4b	Apr 22nd	May 13th	Jul 12th – Sep 27th
Zone 5a	Apr 17th	May 8th	Jul 7th – Sep 30th
Zone 5b	Apr 13th	May 4th	Jul 3rd – Oct 5th
Zone 6a	Apr 10th	May 1st	Jun 30th – Oct 10th
Zone 6b	Apr 4th	Apr 25th	Jun 24th – Oct 16th
Zone 7a	Mar 30th	Apr 20th	Jun 19th – Oct 20th
Zone 7b	Mar 20th	Apr 10th	Jun 9th – Oct 28th
Zone 8a	Mar 11th	Apr 1st	May 31st – Nov 5th
Zone 8b	Mar 2nd	Mar 23rd	May 22nd – Nov 12th
Zone 9a	Feb 13th	Mar 6th	May 5th – Nov 26th
Zone 9b	Jan 19th	Feb 9th	Apr 10th – Dec 9th
Zone 10a	—	Oct 1st	Nov 30th – Feb 28th
Zone 10b	—	Oct 1st	Nov 30th – Feb 28th
Zone 11a	—	Oct 1st	Nov 30th – Feb 28th
Zone 11b	—	Oct 1st	Nov 30th – Feb 28th
Zone 12a	—	Oct 1st	Nov 30th – Feb 28th
Zone 12b	—	Oct 1st	Nov 30th – Feb 28th
Zone 13a	—	Oct 1st	Nov 30th – Feb 28th
Zone 13b	—	Oct 1st	Nov 30th – Feb 28th

Crop Details

Trait	Value
Days to Maturity	60
Sun Requirements	Full Sun
Growth Habit	Upright
Support Needed	None
Planting Depth	Normal
Germination Temp (°F)	75
Min Soil Temp (°F)	60
Min Night Temp (°F)	50
Harden Off (days)	7

Culinary Notes

Chef's Note

Cosmos petals read as airy and lightly sweet, with a crisp snap that makes them worth using fresh rather than cooking down. Treat them like an herb salad leaf—add at the last second so the petals stay satiny and crunchy on the plate.

Best Uses

as a finishing salad topper where they stay satiny and don’t mash
chilled drinks garnish (tea, spritz, or lemonade) for a clean floral note
tiny petals folded into soft cheeses or yogurt for texture contrast
crunchy plating element on tacos, rice bowls, or crudo-style seafood

Flavor Profile

lightly vegetal subtle sweetness crisp, petal-like crunch refreshing floral lift

Kitchen Pairings

lemon olive oil fresh herbs like mint soft cheeses like ricotta seafood like oysters or ceviche

Frequently Asked Questions

What pest or disease commonly affects Cosmos bipinnatus, and how can I control it at home?

Asteraceae plants like Cosmos bipinnatus are commonly bothered by aphids, especially on soft new growth and flower buds. Spray the stems and undersides of leaves with a strong jet of water, then follow with insecticidal soap if you still see colonies after 2–3 days. Watch also for powdery mildew in humid conditions—space plants well, water at the soil line, and remove heavily affected leaves early to slow spread.

How often should I water Cosmos bipinnatus during the main growing phase (after seedlings establish)?

After establishment, water deeply about 1–2 times per week, enough to moisten the root zone but not keep the soil constantly wet. Cosmos bipinnatus prefers evenly moist soil at first, then performs best with drier intervals once plants are actively growing—water when the top 1 inch of soil feels dry. Avoid frequent light watering, which encourages weak growth and increases the chance of mildew.

How do I know when Cosmos bipinnatus is ready to harvest?

Cosmos is ready to harvest once the flower heads are fully open and show crisp, evenly colored ray petals—harvest these for cut flowers. For seed, leave a few blooms to mature until the seed heads turn dry and tan-brown and the seeds are firm; harvest before they begin to disperse. Plan on about 60 days to maturity from sowing under good conditions, with flowers appearing well before full seed readiness.