SproutSmart
SproutSmart™ Intelligent Garden Sowing

Purity

Cosmos
Zone 10b Save Garden

Planting Schedule

Add Purity to your garden to build a schedule and get reminders.
Botanical illustration of Purity
75d to harvest

Feathery petals unfurl in a luminous, airy display—Purity cosmos blooms with a crisp, clean whiteness that seems to glow in the garden. The flowers hold their daisy-like form on sturdy, upright stems, with a light, graceful texture that’s especially striking when grown in generous drifts. Grow Purity for abundant, long-lasting cut-flower color and a breezy, romantic presence that keeps the landscape in constant motion.

Crop Dates

Growing note: In frost-free Zone 10b, grow this cool-season crop during the cooler dry season (October–February).
MilestoneDate
Start Indoors—
ClimateFrost-Free Climate
Transplant / Sow OutdoorsOct 1st
Harvest BeginsDec 15th
Harvest EndsFeb 28th

Crop Details

TraitValue
Days to Maturity75
Sun RequirementsFull SunFull sun
Growth HabitUpright
Support NeededNone
Planting DepthNormal
Germination Temp (°F)70
Min Soil Temp (°F)50
Min Night Temp (°F)45
Harden Off (days)7

Today's Conditions

Outdoor planting for Purity in Zone 10b typically begins around 2026-10-01. Wait until soil reaches at least 50°F before transplanting Purity.

Garden Alerts

In frost-free Zone 10b, grow this cool-season crop during the cooler dry season (October–February).

Recommended Companions

Queen Lime Blush Zinnia
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Lemon Gem Marigold
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Psyche White Cosmos
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Red Gem Marigold
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Sea Shells Cosmos
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Cut And Come Again Zinnia
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Frequently Asked Questions

How often should I water Cosmos bipinnatus during the main growing phase?
Water Cosmos bipinnatus deeply once the top 1 inch of soil dries out, which is typically about 2–3 times per week in warm weather depending on your soil. Keep the soil evenly moist while plants are establishing, but avoid soggy conditions because Cosmos can develop issues in continuously wet soil. During active flowering, prioritize deep, less-frequent watering rather than daily light sprinkling.
How do I know when Cosmos bipinnatus is ready to harvest?
For cut flowers, harvest when the outer petals are fully open and the center disk is mature (about 75 days from sowing for typical plants). Check daily as blooms open in succession—use a clean cut stem in the morning or evening when flowers are crisp. For seed, let spent flowers dry on the plant until the seed heads turn brown and the seeds feel hard, then harvest and dry them a few more days indoors.
Botanical illustration of Purity

Feathery petals unfurl in a luminous, airy display—Purity cosmos blooms with a crisp, clean whiteness that seems to glow in the garden. The flowers hold their daisy-like form on sturdy, upright stems, with a light, graceful texture that’s especially striking when grown in generous drifts. Grow Purity for abundant, long-lasting cut-flower color and a breezy, romantic presence that keeps the landscape in constant motion.

Today's Conditions

Outdoor planting for Purity in Zone 10b typically begins around 2026-10-01. Wait until soil reaches at least 50°F before transplanting Purity.

Garden Alerts

In frost-free Zone 10b, grow this cool-season crop during the cooler dry season (October–February).

Sowing Tips

Soil Temperature

Direct sow or transplant when soil at planting depth holds 50°F for reliable germination and early growth.

Expert Note

For best stems for cutting, start in a sunny spot early, then lightly pinch young plants once to encourage branching before they bloom.