Denver, CO Vegetable Planting Calendar

What to plant now in Denver

In October:

• Plant garlic cloves (Oct 1–14)

The list above is for the month this page was built; the box is refreshed in your browser for today's date.

Spring planting dates

“Plant out” means transplanting for crops started indoors and sowing or planting directly in the garden for the others. Each column applies CSU Extension's timing rule to a different last-frost anchor: aggressive = typical date (Apr 30, 50% risk), balanced = May 4 (30%), safe = May 13 (10%). For hardy crops the cell shows the CSU “as early as” window.

Before sowing, check the soil too. CSU recommends taking its temperature at 4 inches (6 inches for beans). Since NOAA publishes no soil-temperature normals, we give CSU's minimum soil temperature for each crop rather than a date.

Fall planting dates

Latest dates for a fall harvest, using the University of Nebraska–Lincoln Extension count-back formula: days to harvest (CSU) + 14-day fall factor + 14-day frost-tender factor for frost-sensitive crops, counted back from the first-frost date. For transplanted crops (CSU days are from transplant) the result is the latest transplant date; seeds go in CSU's transplant-age weeks earlier. We add no harvest period, so these dates give you a first harvest by the first frost, not a long harvest.

Month-by-month: what to plant in Denver

What to plant in Denver in February

• Start broccoli seeds indoors (Feb 16 – Mar 2)
• Start cabbage seeds indoors (Feb 16 – Mar 2)

What to plant in Denver in March

• Start cauliflower seeds indoors (Mar 2–16)
• Start eggplant seeds indoors (Mar 16 – Apr 6)
• Start pepper seeds indoors (Mar 23 – Apr 6)
• Start broccoli seeds indoors (Feb 16 – Mar 2)
• Start cabbage seeds indoors (Feb 16 – Mar 2)

What to plant in Denver in April

• Onions (dry, from sets): plant sets outdoors (Apr 2–29)
• Peas: direct sow outdoors (Apr 2–29)
• Lettuce (leaf): direct sow outdoors (Apr 2–29)
• Broccoli: transplant outdoors (Apr 2–29)
• Cabbage: transplant outdoors (Apr 2–29)
• Kohlrabi: direct sow outdoors (Apr 2–29)
• Green onions: direct sow outdoors (Apr 2–29)
• Radishes: direct sow outdoors (Apr 2–29)
• Spinach: direct sow outdoors (Apr 2–29)
• Turnips: direct sow outdoors (Apr 2–29)
• Start tomato seeds indoors (Apr 14–28)
• Potatoes: plant (seed pieces) outdoors (Apr 16 – May 13)
• Carrots: direct sow outdoors (Apr 16 – May 13)
• Cauliflower: transplant outdoors (Apr 16 – May 13)
• Beets: direct sow outdoors (Apr 16 – May 13)
• Swiss chard: direct sow outdoors (Apr 16 – May 13)
• Parsnips: direct sow outdoors (Apr 16 – May 13)
• Beans (snap): direct sow outdoors (Apr 30 – May 13)
• Summer squash: direct sow outdoors (Apr 30 – May 13)
• Sweet corn: direct sow outdoors (Apr 30 – May 13)
• Cucumbers: direct sow outdoors (Apr 30 – May 13)
• Start eggplant seeds indoors (Mar 16 – Apr 6)
• Start pepper seeds indoors (Mar 23 – Apr 6)

What to plant in Denver in May

• Peppers: transplant outdoors (May 14–27)
• Eggplant: transplant outdoors (May 14–27)
• Cantaloupe: direct sow outdoors (May 14–27)
• Watermelon: direct sow outdoors (May 14–27)
• Winter squash: direct sow outdoors (May 14–27)
• Start cabbage seeds indoors for a fall crop (May 17–31)
• Potatoes: plant (seed pieces) outdoors (Apr 16 – May 13)
• Carrots: direct sow outdoors (Apr 16 – May 13)
• Cauliflower: transplant outdoors (Apr 16 – May 13)
• Beets: direct sow outdoors (Apr 16 – May 13)
• Swiss chard: direct sow outdoors (Apr 16 – May 13)
• Parsnips: direct sow outdoors (Apr 16 – May 13)
• Beans (snap): direct sow outdoors (Apr 30 – May 13)
• Summer squash: direct sow outdoors (Apr 30 – May 13)
• Sweet corn: direct sow outdoors (Apr 30 – May 13)
• Cucumbers: direct sow outdoors (Apr 30 – May 13)

What to plant in Denver in June

• Tomatoes: transplant outdoors (Jun 2)
• Start broccoli seeds indoors for a fall crop (Jun 6–20)

What to plant in Denver in July

• Last day to set out cabbage transplants for a fall harvest (by Jul 5)
• Last day to sow beans (snap) for a fall harvest (by Jul 16)
• Last day to sow carrots for a fall harvest (by Jul 20)
• Last day to sow cucumbers for a fall harvest (by Jul 21)
• Last day to sow peas for a fall harvest (by Jul 25)
• Last day to set out broccoli transplants for a fall harvest (by Jul 25)
• Last day to sow summer squash for a fall harvest (by Jul 26)
• Last day to sow lettuce (leaf) for a fall harvest (by Jul 30)
• Last day to sow green onions for a fall harvest (by Jul 30)
• Last day to sow beets for a fall harvest (by Jul 30)
• Last day to sow swiss chard for a fall harvest (by Jul 30)

What to plant in Denver in August

• Last day to sow kohlrabi for a fall harvest (by Aug 9)
• Last day to sow turnips for a fall harvest (by Aug 9)
• Last day to sow spinach for a fall harvest (by Aug 19)
• Last day to sow radishes for a fall harvest (by Aug 29)

What to plant in Denver in October

• Plant garlic cloves (Oct 1–14)

Crop-by-crop notes

When to plant tomatoes in Denver

Very tender crop. CSU Extension's rules are to set tomatoes out at least 2 weeks after the average last frost and only once nights are above 52°F. In Denver, the frost rule alone would allow about May 14, but the average nightly low at Denver Water Dept. isn't above 52°F until Jun 2, so the night rule sets the date at every risk level: about Jun 2. Start seeds indoors Apr 14–28, 5–7 weeks before transplanting on Jun 2. Fruit set suffers when nights drop below 55°F (CSU). The normal low at Denver Water Dept. reaches 55°F on Jun 12. CSU's typical time from transplant to harvest for tomato plants is 65 days. Set out on Jun 2, they would start producing around Aug 6, 67 days before the typical first frost (Oct 12).

When to plant peppers in Denver

Very tender crop. CSU Extension's rule is to set peppers out at least 2 weeks after the average last frost. That's about May 14 using the typical date, May 18 as a balanced choice, or May 27 if you go by the safer 10% date. Start seeds indoors Mar 23 – Apr 6, 6–8 weeks before transplanting on May 18. Fruit set suffers when nights drop below 55°F (CSU). The normal low at Denver Water Dept. reaches 55°F on Jun 12. Using CSU's typical 70 days from transplant to harvest, pepper plants set out on May 18 would start producing around Jul 27. That's 77 days before the typical first frost (Oct 12).

When to plant potatoes in Denver

Semi-hardy crop. CSU says potatoes can be planted as early as 0–2 weeks before the average last frost, in soil of at least 45°F. In Denver, that's roughly Apr 16–30 going by the typical date, or Apr 29 – May 13 going by the safer date.

When to plant onions (dry, from sets) in Denver

Hardy crop. CSU says onions (dry, from sets) can go in as early as 2–4 weeks before the average last frost, once the soil can be worked and is at least 35°F. In Denver, that's roughly Apr 2–16 going by the typical date, or Apr 15–29 going by the safer date.

When to plant peas in Denver

Hardy crop. CSU says peas can go in as early as 2–4 weeks before the average last frost: roughly Apr 2–16 in Denver using the typical date, or Apr 15–29 using the safer one. Wait until the soil can be worked and is at least 40°F. For fall, count back 79 days from the first-frost date. That means sowing by Jul 25, or by Jul 11 to be safe.

When to plant lettuce (leaf) in Denver

Hardy crop. Per CSU, lettuce (leaf) can be planted as early as 2–4 weeks before the average last frost, as long as the soil is workable and at least 35°F. For Denver, that works out to roughly Apr 2–16 (typical date) or Apr 15–29 (safer date). For fall, count back 74 days from the first-frost date. That means sowing by Jul 30, or by Jul 16 to be safe.

When to plant carrots in Denver

Semi-hardy crop. CSU says carrots can be planted as early as 0–2 weeks before the average last frost, in soil of at least 40°F. In Denver, that's roughly Apr 16–30 going by the typical date, or Apr 29 – May 13 going by the safer date. For a fall crop, sow by Jul 20, or by Jul 6 to be safe. That's 84 days back from the first-frost date.

When to plant beans (snap) in Denver

Tender crop. CSU says to sow beans (snap) around the average last frost, about Apr 30 in Denver. If you want only a 1-in-10 chance of a later 32°F night, wait until May 13. Seeds need soil of at least 55°F. For fall, sow by Jul 16 (Jul 2 to be safe), which is 88 days before the first-frost date.

When to plant summer squash in Denver

Tender crop. CSU's timing for summer squash is around the average last frost, which is about Apr 30 in Denver. For only a 1-in-10 chance of a later 32°F night, hold off until May 13. Seeds want soil at 60°F or warmer. For a fall crop, sow by Jul 26, or by Jul 12 to be safe. That's 78 days back from the first-frost date.

When to plant broccoli in Denver

Hardy crop. CSU says broccoli can go in as early as 2–4 weeks before the average last frost, once the soil can be worked and is at least 40°F. In Denver, that's roughly Apr 2–16 going by the typical date, or Apr 15–29 going by the safer date. CSU's typical time from transplant to harvest for broccoli plants is 65 days. Set out on Apr 6, they would start producing around Jun 10, 124 days before the typical first frost (Oct 12). Fall broccoli: set transplants out by Jul 25. The date counts back from the typical first frost (Oct 12) by UNL Extension's method, using CSU's 65 days from transplant to harvest. Home-grown transplants need seeds started Jun 6–20 (CSU: 5–7 weeks).

When to plant cabbage in Denver

Hardy crop. Per CSU, cabbage can be planted as early as 2–4 weeks before the average last frost, as long as the soil is workable and at least 40°F. For Denver, that works out to roughly Apr 2–16 (typical date) or Apr 15–29 (safer date). Set out on Apr 6, cabbage plants would start producing around Jun 30, based on CSU's typical 85 days from transplant to harvest. That leaves 104 days before the typical first frost (Oct 12). For a fall crop, set cabbage transplants out by Jul 5. That's UNL Extension's count-back from the typical first frost (Oct 12), using CSU's 85 days from transplant to harvest. If you grow your own transplants, start seeds May 17–31 (CSU: 5–7 weeks to transplant size).

When to plant cauliflower in Denver

Semi-hardy crop. CSU says cauliflower can be planted as early as 0–2 weeks before the average last frost, in soil of at least 40°F. In Denver, that's roughly Apr 16–30 going by the typical date, or Apr 29 – May 13 going by the safer date.

When to plant kohlrabi in Denver

Hardy crop. Per CSU, kohlrabi can be planted as early as 2–4 weeks before the average last frost, as long as the soil is workable and at least 40°F. For Denver, that works out to roughly Apr 2–16 (typical date) or Apr 15–29 (safer date). For fall, count back 64 days from the first-frost date. That means sowing by Aug 9, or by Jul 26 to be safe.

When to plant green onions in Denver

Hardy crop. Per CSU, green onions can be planted as early as 2–4 weeks before the average last frost, as long as the soil is workable and at least 35°F. For Denver, that works out to roughly Apr 2–16 (typical date) or Apr 15–29 (safer date). For fall, count back 74 days from the first-frost date. That means sowing by Jul 30, or by Jul 16 to be safe.

When to plant radishes in Denver

Hardy crop. Per CSU, radishes can be planted as early as 2–4 weeks before the average last frost, as long as the soil is workable and at least 40°F. For Denver, that works out to roughly Apr 2–16 (typical date) or Apr 15–29 (safer date). For fall, count back 44 days from the first-frost date. That means sowing by Aug 29, or by Aug 15 to be safe.

When to plant spinach in Denver

Hardy crop. CSU says spinach can go in as early as 2–4 weeks before the average last frost: roughly Apr 2–16 in Denver using the typical date, or Apr 15–29 using the safer one. Wait until the soil can be worked and is at least 40°F. For a fall crop, sow by Aug 19, or by Aug 5 to be safe. That's 54 days back from the first-frost date.

When to plant turnips in Denver

Hardy crop. CSU says turnips can go in as early as 2–4 weeks before the average last frost, once the soil can be worked and is at least 40°F. In Denver, that's roughly Apr 2–16 going by the typical date, or Apr 15–29 going by the safer date. For fall, sow by Aug 9 (Jul 26 to be safe), which is 64 days before the first-frost date.

When to plant beets in Denver

Semi-hardy crop. CSU says beets can be planted as early as 0–2 weeks before the average last frost, in soil of at least 40°F. In Denver, that's roughly Apr 16–30 going by the typical date, or Apr 29 – May 13 going by the safer date. For a fall crop, sow by Jul 30, or by Jul 16 to be safe. That's 74 days back from the first-frost date.

When to plant swiss chard in Denver

Semi-hardy crop. CSU says swiss chard can be planted as early as 0–2 weeks before the average last frost, in soil of at least 40°F. In Denver, that's roughly Apr 16–30 going by the typical date, or Apr 29 – May 13 going by the safer date. For a fall crop, sow by Jul 30, or by Jul 16 to be safe. That's 74 days back from the first-frost date.

When to plant parsnips in Denver

Semi-hardy crop. Per CSU, parsnips can go in as early as 0–2 weeks before the average last frost: roughly Apr 16–30 in Denver (typical date) or Apr 29 – May 13 (safer date). The soil should be at least 35°F.

When to plant sweet corn in Denver

Tender crop. Sow sweet corn around the average last frost, per CSU: about Apr 30 in Denver. Waiting until May 13 cuts the chance of a later 32°F night to 1 in 10. Seeds need soil of at least 50°F.

When to plant cucumbers in Denver

Tender crop. CSU's timing for cucumbers is around the average last frost, which is about Apr 30 in Denver. For only a 1-in-10 chance of a later 32°F night, hold off until May 13. Seeds want soil at 60°F or warmer. For fall, sow by Jul 21 (Jul 7 to be safe), which is 83 days before the first-frost date.

When to plant eggplant in Denver

Very tender crop. CSU Extension's rule is 2+ weeks after the average last frost, which puts eggplant outside around May 14 (typical date), May 18 (balanced) or May 27 (safer 10% date). Start seeds indoors Mar 16 – Apr 6, 6–9 weeks ahead of transplanting on May 18. Set out on May 18, eggplant plants would start producing around Jul 17, based on CSU's typical 60 days from transplant to harvest. That leaves 87 days before the typical first frost (Oct 12).

When to plant cantaloupe in Denver

Very tender crop. CSU Extension's rule is to plant cantaloupe at least 2 weeks after the average last frost. That's about May 14 using the typical date, May 18 as a balanced choice, or May 27 if you go by the safer 10% date. Seeds need soil of at least 60°F.

When to plant watermelon in Denver

Very tender crop. CSU Extension says to plant watermelon 2+ weeks after the average last frost: about May 14 (typical date), May 18 (balanced) or May 27 (safer 10% date). Wait for soil of at least 60°F.

When to plant winter squash in Denver

Very tender crop. CSU Extension says to plant winter squash 2+ weeks after the average last frost: about May 14 (typical date), May 18 (balanced) or May 27 (safer 10% date). Wait for soil of at least 60°F.

When to plant garlic in Denver

Plant garlic in early October, before October 15 (Oct 1–14), per CSU Extension's Colorado guidance. This window is fixed statewide and isn't based on frost data. The typical first hard freeze (28°F) at Denver Water Dept. comes on Oct 21, 7 days after it ends.

How these dates are calculated

CSU states its spring rules relative to “the average last spring frost.” We use the 50% date as that average and also show the 30% and 10% anchors. See the methodology for details and limitations.

FAQ

When should I start seeds indoors in Denver?

Start tomatoes Apr 14–28 and peppers Mar 23 – Apr 6. Both dates count back from a balanced (30%-risk) transplant date using CSU's transplant ages.

When should I plant tomatoes outside in Denver?

About Jun 2, at every risk level. CSU wants tomatoes out 2+ weeks after the average last frost (that rule alone gives about May 14 here) and nights above 52°F. At Denver Water Dept., the average nightly low first rises above 52°F on Jun 2, later than the frost-rule date, so the night rule sets the date.

What can I plant in Denver in the fall?

Counting back from the typical first frost (Oct 12) with UNL Extension's method: peas by Jul 25; lettuce (leaf) by Jul 30; carrots by Jul 20; beans (snap) by Jul 16; summer squash by Jul 26; broccoli by Jul 25 (transplants); cabbage by Jul 5 (transplants); kohlrabi by Aug 9; green onions by Jul 30; radishes by Aug 29; spinach by Aug 19; turnips by Aug 9; beets by Jul 30; swiss chard by Jul 30; cucumbers by Jul 21. Garlic goes in Oct 1–14.

When should I plant garlic in Denver?

CSU Extension's Colorado guidance is early October, before October 15 (Oct 1–14).

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