Denver, CO planting zone & frost dates
Denver is in USDA hardiness zone 6a. The last spring frost usually comes around April 30 and the first fall frost around October 12, for a growing season of about 165 days.
Planting calendar for Denver
Dates are counted from the average last spring frost (April 30) using the typical timing recommended by U.S. extension services. Warm-season crops go out only after the danger of frost has passed and the soil has warmed.
| Crop | When |
|---|---|
| Tomatoes | Start seeds indoors: Mar 5 – Mar 19 Transplant outdoors: May 7 – May 14 |
| Peppers | Start seeds indoors: Feb 19 – Mar 5 Transplant outdoors: May 14 – May 21 |
| Eggplant | Start seeds indoors: Feb 19 – Mar 5 Transplant outdoors: May 14 – May 21 |
| Broccoli | Start seeds indoors: Feb 19 – Mar 5 Transplant outdoors: Apr 2 – Apr 16 |
| Cabbage | Start seeds indoors: Feb 19 – Mar 5 Transplant outdoors: Apr 2 – Apr 16 |
| Onions (sets) | Plant outdoors: Apr 2 – Apr 16 |
| Peas | Sow outdoors: Mar 19 – Apr 2 |
| Spinach | Sow outdoors: Mar 19 – Apr 2 |
| Lettuce | Sow outdoors: Apr 2 – Apr 16 |
| Carrots | Sow outdoors: Apr 2 – Apr 16 |
| Potatoes | Plant outdoors: Apr 2 – Apr 16 |
| Beans | Sow outdoors: May 7 – May 14 |
| Sweet corn | Sow outdoors: May 7 – May 14 |
| Cucumbers | Sow outdoors: May 7 – May 14 |
| Squash & zucchini | Sow outdoors: May 7 – May 14 |
| Basil | Start seeds indoors: Mar 19 – Apr 2 Transplant outdoors: May 7 – May 14 |
Fall garden: cool-season crops like lettuce, spinach and kale can be sown again around Aug 17 (8 weeks before the average first fall frost on Oct 12).
Useful for zone 6a gardens
- Seed starting kit with dome — to start seeds indoors before the last frost
- LED grow light for seedlings — stops leggy seedlings
- Frost cloth / plant covers — for late spring and early fall frosts
- Soil thermometer — warm-season crops need soil above 60°F
- Cold frame / mini greenhouse — adds weeks to a short season
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Frost risk in detail
| 90% chance | 50% chance | 10% chance | |
|---|---|---|---|
| Last 32°F frost in spring is after | Apr 15 | Apr 30 | May 13 |
| First 32°F frost in fall is before | Oct 26 | Oct 12 | Sep 28 |
How to read it: in spring there is a 10% chance of a frost after May 13, so that is a safe date for tender plants. In fall there is a 10% chance of frost before September 28. A hard freeze (28°F) usually ends around April 18.
Hardiness zone by ZIP code in Denver
- 80201 zone 6a
- 80202 zone 6a
- 80203 zone 6a
- 80204 zone 6a
- 80205 zone 6a
- 80206 zone 6a
- 80207 zone 6a
- 80208 zone 6a
- 80209 zone 6a
- 80210 zone 6a
- 80211 zone 6a
- 80212 zone 6a
- 80214 zone 6a
- 80215 zone 6a
- 80216 zone 6a
- 80217 zone 6a
- 80218 zone 6a
- 80219 zone 6a
- 80220 zone 6a
- 80221 zone 6a
- 80222 zone 6a
- 80223 zone 6a
- 80224 zone 6a
- 80226 zone 6a
- 80227 zone 6a
- 80228 zone 6a
- 80229 zone 6a
- 80230 zone 6a
- 80231 zone 6a
- 80232 zone 6a
- 80233 zone 6a
- 80234 zone 6a
- 80235 zone 6a
- 80236 zone 6a
- 80237 zone 6a
- 80238 zone 6a
- 80239 zone 6a
- 80243 zone 6a
- 80244 zone 6a
- 80246 zone 6a
- 80247 zone 6a
- 80248 zone 6a
- 80249 zone 6a
- 80250 zone 6a
- 80256 zone 6a
- 80257 zone 6a
- 80259 zone 6a
- 80260 zone 6a
- 80261 zone 6a
- 80262 zone 6a
- 80263 zone 6a
- 80266 zone 6a
- 80271 zone 6a
- 80273 zone 6a
- 80274 zone 6a
- 80281 zone 6a
- 80290 zone 6a
- 80291 zone 6a
- 80299 zone 6a
Nearby cities
- Berkley zone 6a, last frost May 5
- Commerce City zone 6a, last frost May 4
- Englewood zone 6a, last frost May 2
- Wheat Ridge zone 6a, last frost May 5
- Sherrelwood zone 6a, last frost May 2
- Welby zone 6a, last frost May 2
- Lakewood zone 6a, last frost May 3
- Westminster zone 6a, last frost May 2
Questions
What growing zone is Denver, CO?
Denver is in USDA Plant Hardiness Zone 6a (average extreme winter low -10°F to -5°F), according to the USDA 2023 map.
When is the last frost in Denver?
The average last spring frost (32°F) in Denver is April 30. There is still a 10% chance of frost until May 13.
When can I plant tomatoes in Denver?
Transplant tomatoes outdoors 1–2 weeks after the average last frost: around May 7 – May 14. Start seeds indoors 6–8 weeks before the last frost.
Frost dates: NOAA U.S. Climate Normals 1991–2020, station Denver Water Dept, CO (USC00052223), 2.3 km (1.4 mi) from the city center, elevation 1594 m, based on 22 years of records. Hardiness zone: USDA Plant Hardiness Zone Map 2023 for the ZIP code nearest to the city center. Microclimates (valleys, hills, cities, coasts) can be warmer or colder: check the local forecast before planting. How we calculate the data.