427 saves
Cosmos
We track 20 varieties; the ones most used by real gardeners.
The 19 most-saved Cosmos varieties
Browse all 20 Cosmos varieties →
2 species of Cosmos
Each one is a parent of the varieties above.
Track your Cosmos in Sow
Save the Cosmos you grow and get care reminders timed to your zone.
How to grow Cosmos
Whats common across all Cosmos varieties in our catalog — drawn from the care records of the 20 most-grown of them.
The Cosmos year
- PlantApril and May100% of varieties
Direct sow seeds or transplant seedlings after danger of frost
- DeadheadJune–September100% of varieties
Remove spent blooms regularly to encourage continuous flowering
- HarvestJune–September60% of varieties
Cut stems when flowers are half open for best vase life
- StakeMay and June35% of varieties
Stake taller plants early, especially in windy locations.
- FertilizeMay and June30% of varieties
Apply low-nitrogen fertilizer sparingly; too much causes weak stems.
Do
- Water deeply once a week during dry spells 🌱
- Use well-draining soil to prevent root rot
- Provide full sun for optimal flowering
- Deadhead to promote more flowers
- Mulch to retain soil moisture and suppress weeds
Avoid
- Avoid overwatering to prevent root rot ❌
- Avoid overwatering, which can cause root rot ❌
- Don’t fertilize late in the season to prevent legginess
- Do not disturb roots during peak flowering
What goes wrong with Cosmos
| Problem | What you'll see | What to do |
|---|---|---|
| Aphids | Sticky residue and distorted leaves | Spray with insecticidal soap or neem oil |
| Spider mites | Fine webbing and speckled leaves | Use horticultural oil or insecticidal soap |
| Spider Mites | Fine webbing and speckled leaves | Increase humidity and spray with insecticidal soap |
| Powdery mildew | White powdery coating on leaves | Apply organic fungicide and improve air circulation |
| Powdery Mildew | White powder on leaves | Improve air circulation and apply fungicide |
| Powdery mildew | White powder on leaves | Improve air circulation and apply fungicide |
| Root rot | Wilting despite watering | Ensure well-draining soil and reduce watering |
Making more Cosmos
Cuttings
- Select healthy stems in summer.
- Mist cuttings and place in moist soil for 4-6 weeks.
- Provide indirect sunlight for root development.
Seed
- Tuck seeds into moist soil in early spring.
- Keep soil consistently moist for 2 weeks.
- Thin seedlings to 12 inches apart after germination.
Cosmos questions
How many types of Cosmos are there?
The Sow catalog tracks 20 distinct Cosmos varieties. The most popular — ranked by 427 real gardeners — are shown first above.
What zones does Cosmos grow in?
Across its varieties, Cosmos covers USDA Zones 5–10. Individual varieties differ — each plant page lists its exact range, and Sow filters the catalog to your zone automatically.
When does Cosmos bloom?
Most Cosmos varieties bloom in mid-summer, summer to fall, summer to fall. Staggering early, mid, and late varieties extends the genus's season in one bed.
Which Cosmos should I choose?
Start from the most-saved varieties above — popularity across thousands of gardens is a strong signal of reliability — then filter by your zone and sun. In the Sow app you can preview any of them in a photo of your actual yard before you buy.