When to Plant Cosmos in Vermont
Delicate, daisy-like blooms that dance in the breeze. Cosmos thrive in poor soil and practically grow themselves.
The Short Answer
Vermont Frost Dates
Your planting dates depend on which part of Vermont you're in. Here are the frost date ranges by region:
| Region | Zones | Last Frost (Spring) | First Frost (Fall) |
|---|---|---|---|
| Northern Vermont | 3b, 4a | May 20 - Jun 5 | Sep 5 - Sep 20 |
| Central Vermont | 4a, 4b, 5a | May 10 - May 25 | Sep 15 - Oct 1 |
| Southern Vermont | 4b, 5a, 5b | May 5 - May 20 | Sep 20 - Oct 5 |
Cosmos Planting Schedule for Vermont
Northern Vermont (Zones 3b, 4a)
Average last frost: May 20 - Jun 5 · Average first frost: Sep 5 - Sep 20
Central Vermont (Zones 4a, 4b, 5a)
Average last frost: May 10 - May 25 · Average first frost: Sep 15 - Oct 1
Southern Vermont (Zones 4b, 5a, 5b)
Average last frost: May 5 - May 20 · Average first frost: Sep 20 - Oct 5
Growing Cosmos in Vermont
Cosmos in Vermont's Climate
Cosmos bloom reliably even in short-season gardens — direct sow after last frost and enjoy graceful flowers from July through hard frost. They actually prefer poor soil and minimal water, making them one of the lowest-maintenance flowers in any climate. Self-seed for volunteer plants next year.
Soil Considerations for Vermont
Rocky, acidic soils typical of New England. Glacial deposits. Thin mountain soils. Raised beds very popular. Make sure soil has warmed to at least 60°F before planting cosmos outside.
Vermont Climate & Growing Season
Short growing season. Cold winters. Cool summers. Long summer days help compensate. Season extension techniques valuable. 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 Vermont: Northern Vermont (3b, 4a) has a last frost around May 20 - Jun 5, while Southern Vermont (4b, 5a, 5b) sees frost end around May 5 - May 20. 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