State growing guide
Colorado Planting Guide
USDA Zone 5a/5b · Last frost May 10 · First frost Oct 3 · 146 days
Zone-specific planting calendar, major city frost dates, top crops, and Duke's tips for growing food in Colorado.
Frost Dates by City — Colorado
Average frost dates for major Colorado cities. Use these to calculate your indoor start dates and transplant windows.
| City | USDA Zone | Last Spring Frost | First Fall Frost | Tomato Transplant Window |
|---|---|---|---|---|
| Denver | 5b | May 5 | Oct 5 | ~2 wks after (May 5) |
| Colorado Springs | 5a | May 15 | Sep 30 | ~2 wks after (May 15) |
| Grand Junction | 6a | Apr 20 | Oct 20 | ~2 wks after (Apr 20) |
| Fort Collins | 5b | May 8 | Oct 2 | ~2 wks after (May 8) |
| Boulder | 5b | May 7 | Oct 3 | ~2 wks after (May 7) |
| Pueblo | 6a | Apr 25 | Oct 15 | ~2 wks after (Apr 25) |
Average dates based on 30-year NOAA climate normals. Individual years may vary ±2 weeks. Use the Zone Lookup Tool for ZIP-specific dates.
Duke's Top Tips for Colorado Gardeners
- Denver last frost is May 5 — don't transplant tomatoes before then
- Cover plants with frost blankets in May for late surprise frosts
- High altitude means more UV — plants need afternoon shade in summer
- Grand Junction (Zone 6a) is the best growing area in Colorado
- Wall O' Waters let you plant tomatoes 3–4 weeks early
Common Challenges in Colorado
- ⚠ Short growing season — 130–160 days depending on elevation
- ⚠ Late May/early June surprise frosts hit every few years
- ⚠ Hail storms are common July–August — use row covers or hail nets
- ⚠ High altitude UV stresses plants — mulch is essential
Best Crops for Colorado
Get exact dates for your ZIP code in Colorado
City averages are a starting point. Your actual microclimate matters — enter your ZIP for precise frost dates.
Frequently Asked Questions — Colorado Gardening
What zone is Colorado?
Colorado ranges from Zone 3 in the high mountains to Zone 6b in the Grand Junction area. Denver is Zone 5b, Colorado Springs is Zone 5a, and the Western Slope is Zone 5–6.
When is the last frost in Denver?
Denver's average last frost date is May 5, but late May frosts are common. For reliable transplanting, many Denver gardeners wait until May 10–15 or use Wall O' Waters for protection.
Can I grow tomatoes in Colorado?
Yes, but choose short-season varieties (65–75 days) like Early Girl, Celebrity, or Glacier. Plant through black plastic mulch to warm the soil.