Calendars by city / CO
Denver, Colorado vegetable planting calendar
Planting windows for Denver, Colorado built from the NOAA 1991–2020 freeze normals at DENVER INTERNATIONAL AIRPORT, CO US (station USW00003017), not from a hardiness zone.
Denver, Colorado planting dates for 27 vegetables
The same windows as a table
Each row applies a published extension rule to the frost dates above. Hardy crops go out 2–4 weeks before the last frost; semi-hardy crops 0–2 weeks before; tender crops around the frost date; very tender crops 2 or more weeks after. The last fall planting date counts the crop's days to harvest back from the first fall frost. The rules and their sources are on the methodology page.
| Crop | Frost class | Start seeds indoors | Plant outdoors | Last fall planting | Days to harvest |
|---|---|---|---|---|---|
| Beets | Semi-hardy | — (direct sow) | Direct sow: Apr 22 – May 6 | Aug 14 | 60 |
| Broccoli | Hardy | Feb 18 – Mar 18 | Transplant: Apr 8 – Apr 22 | Aug 16 | 65 (from transplant) |
| Cabbage | Hardy | Feb 18 – Mar 18 | Transplant: Apr 8 – Apr 22 | Jul 27 | 85 (from transplant) |
| Carrots | Semi-hardy | — (direct sow) | Direct sow: Apr 22 – May 6 | Aug 4 | 70 |
| Cauliflower | Semi-hardy | Mar 4 – Apr 1 | Transplant: Apr 22 – May 6 | Aug 9 | 65 (from transplant) |
| Kohlrabi | Hardy | — (direct sow) | Direct sow: Apr 8 – Apr 22 | Aug 31 | 50 |
| Lettuce (leaf) | Hardy | — (direct sow) | Direct sow: Apr 8 – Apr 22 | Aug 21 | 60 |
| Onions (green) | Hardy | — (direct sow) | Direct sow: Apr 8 – Apr 22 | Aug 21 | 60 |
| Onions (dry, from seed) | Hardy | — (direct sow) | Direct sow: Apr 8 – Apr 22 | Jul 2 | 110 |
| Onions (dry, from sets) | Hardy | — (direct sow) | Plant sets: Apr 8 – Apr 22 | Jul 2 | 110 |
| Parsnips | Semi-hardy | — (direct sow) | Direct sow: Apr 22 – May 6 | Aug 4 | 70 |
| Peas | Hardy | — (direct sow) | Direct sow: Apr 8 – Apr 22 | Aug 16 | 65 |
| Potatoes | Semi-hardy | — (direct sow) | Plant seed potatoes: Apr 22 – May 6 | Jun 10 | 125 |
| Radishes | Hardy | — (direct sow) | Direct sow: Apr 8 – Apr 22 | Sep 20 | 30 |
| Spinach | Hardy | — (direct sow) | Direct sow: Apr 8 – Apr 22 | Sep 10 | 40 |
| Swiss chard | Semi-hardy | — (direct sow) | Direct sow: Apr 22 – May 6 | Aug 14 | 60 |
| Turnips | Hardy | — (direct sow) | Direct sow: Apr 8 – Apr 22 | Aug 31 | 50 |
| Snap beans | Tender | — (direct sow) | Direct sow: May 6 – May 13 | Aug 7 | 60 |
| Cantaloupe | Very tender | Apr 29 – May 20 | Direct sow (or transplant): May 20 – Jun 3 | Jul 13 | 85 |
| Sweet corn | Tender | — (direct sow) | Direct sow: May 6 – May 13 | Jul 8 | 60–90 |
| Cucumbers | Tender | Apr 15 – Apr 29 | Direct sow (or transplant): May 6 – May 13 | Aug 12 | 55 |
| Eggplant | Very tender | Mar 18 – Apr 22 | Transplant: May 20 – Jun 3 | Aug 7 | 60 (from transplant) |
| Peppers | Very tender | Mar 25 – Apr 22 | Transplant: May 20 – Jun 3 | Jul 28 | 70 (from transplant) |
| Tomatoes | Very tender | Apr 1 – Apr 29 | Transplant: May 20 – Jun 3 | Aug 2 | 65 (from transplant) |
| Summer squash | Tender | Apr 15 – Apr 29 | Direct sow (or transplant): May 6 – May 13 | Aug 17 | 50 |
| Winter squash | Very tender | Apr 29 – May 20 | Direct sow (or transplant): May 20 – Jun 3 | No separate fall sowing | 100 |
| Watermelon | Very tender | Apr 29 – May 20 | Direct sow (or transplant): May 20 – Jun 3 | Jul 13 | 85 |
What the Denver, Colorado frost-free season means for your choices
At 153 frost-free days, Denver, Colorado gardeners should compare that number to the days-to-harvest column before buying seed. A crop whose days to harvest plus its transplant age is close to the season length needs either an early start indoors or a short-season variety.
- Hardy crops (peas, spinach, radishes, lettuce, broccoli, cabbage) can go in from about Apr 8 – Apr 22 and again for fall.
- Very tender crops (tomatoes, peppers, eggplant, melons, winter squash) should wait until May 20 – Jun 3; start tomato seeds indoors Apr 1 – Apr 29.
- Fall sowing is worthwhile only for the rows that show a separate fall date; for the others the spring window already covers the season.
Denver, CO planting questions
When is the last frost in Denver, Colorado?
The 50% probability date for the last spring 32°F reading at DENVER INTERNATIONAL AIRPORT, CO US is May 6, from the NOAA 1991–2020 climate normals. In half the years on that record the last frost came later than that date, so tender crops are safer a week or two after it. The last 28°F hard freeze averages Apr 28.
When can I plant tomatoes in Denver, Colorado?
Tomatoes are a very tender crop, so the Colorado State Extension rule puts them out 2 or more weeks after the last spring frost: May 20 – Jun 3 in Denver, Colorado. Start the seeds indoors Apr 1 – Apr 29, which is 5 to 7 weeks before that transplant window.
How long is the growing season in Denver, Colorado?
Denver, Colorado averages 153 frost-free days, between the 50% last spring frost on May 6 and the 50% first fall frost on Oct 6 at DENVER INTERNATIONAL AIRPORT, CO US. Check a variety's days to harvest against that number before buying seed.
When should I start seeds indoors in Denver, Colorado?
The earliest indoor sowing on this calendar is broccoli and cabbage at Feb 18 – Mar 18. Hardy crops are transplanted out Apr 8 – Apr 22 here, and each crop's indoor window is simply its outdoor window minus the transplant age published by Colorado State Extension, so nothing starts earlier than that.
What can I plant in fall in Denver, Colorado?
The crops with a separate fall sowing here, latest first, are radishes, spinach, kohlrabi, turnips, lettuce (leaf) and onions (green), plus 20 more on the chart above. Each fall date counts the crop's days to harvest back from the first fall frost on Oct 6, plus an allowance for frost-tolerant crops that is our own assumption, not the source's.
Station data and limitations
| NOAA station | DENVER INTERNATIONAL AIRPORT, CO US (USW00003017) |
|---|---|
| Location | 39.8328, -104.6575 · elevation 1650.2 m |
| Last spring 32°F / 28°F (50%) | May 6 / Apr 28 |
| First fall 32°F / 28°F (50%) | Oct 6 / Oct 16 |
| Dataset | NOAA/NCEI U.S. Climate Normals 1991–2020, annual/seasonal product, data types ANN-TMIN-PRBLST/PRBFST-T32FP50 and T28FP50 |
| Retrieved | 2026-10-16 |
The normals describe the airport station, not your yard. They are averages of a 30-year record and say nothing about this year's weather. Watch the local forecast around the dates shown, and use soil temperature for warm-season crops, which the Colorado State guide treats as the better signal.
Nearby calendars
- Salt Lake City, Utah — last spring frost Apr 21
- Omaha, Nebraska — last spring frost Apr 21
- Oklahoma City, Oklahoma — last spring frost Mar 27
- Kansas City, Missouri — last spring frost Apr 12
Read the method behind these dates: last frost date vs hardiness zone.