When to Plant Cosmos in Nevada
Delicate, daisy-like blooms that dance in the breeze. Cosmos thrive in poor soil and practically grow themselves.
The Short Answer
Nevada Frost Dates
Your planting dates depend on which part of Nevada you're in. Here are the frost date ranges by region:
| Region | Zones | Last Frost (Spring) | First Frost (Fall) |
|---|---|---|---|
| Northern Nevada (Reno) | 6b, 7a | May 1 - May 20 | Sep 25 - Oct 15 |
| Las Vegas | 8b, 9a, 9b | Feb 10 - Mar 5 | Nov 10 - Dec 1 |
| Mountain Nevada | 4a, 4b, 5a, 5b | May 25 - Jun 15 | Aug 25 - Sep 15 |
Cosmos Planting Schedule for Nevada
Northern Nevada (Reno) (Zones 6b, 7a)
Average last frost: May 1 - May 20 · Average first frost: Sep 25 - Oct 15
Las Vegas (Zones 8b, 9a, 9b)
Average last frost: Feb 10 - Mar 5 · Average first frost: Nov 10 - Dec 1
Mountain Nevada (Zones 4a, 4b, 5a, 5b)
Average last frost: May 25 - Jun 15 · Average first frost: Aug 25 - Sep 15
Growing Cosmos in Nevada
Cosmos in Nevada's Climate
Cosmos grow during the drier months in subtropical zones. Cosmos sulphureus (Bright Lights) handles humidity better than Cosmos bipinnatus (Sensation). Avoid peak summer humidity periods. The flowers are so low-maintenance that they essentially grow as wildflowers in mild climates.
Soil Considerations for Nevada
Desert soils — alkaline, low organic matter. Extremely dry. Heavy amendment essential. Irrigation required. Make sure soil has warmed to at least 60°F before planting cosmos outside.
Nevada Climate & Growing Season
Arid climate. Extreme heat in summer (Las Vegas). Short season at altitude. Very low humidity. Water conservation critical. Cosmos cannot tolerate any frost, so wait until all frost danger has passed before transplanting outside. Watch local forecasts carefully in spring.
Growing season length varies across Nevada: Northern Nevada (Reno) (6b, 7a) has a last frost around May 1 - May 20, while Mountain Nevada (4a, 4b, 5a, 5b) sees frost end around May 25 - Jun 15. This difference matters for cosmos — transplant timing shifts by several weeks across the state.
Growing Tips
Don't over-fertilize — rich soil produces more leaves and fewer flowers. Let some flowers go to seed for next year's crop.
Companion Planting
Plant cosmos alongside these companions for better growth:
The Bottom Line
Last reviewed: March 29, 2026