Centennial, CO Vegetable Planting Calendar

What to plant now in Centennial

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 (May 5, 50% risk), balanced = May 10 (30%), safe = May 17 (10%). For hardy crops the cell shows the CSU “as early as” window.

Frost odds aren't the only check. CSU recommends measuring soil temperature at 4 inches (6 inches for beans) before you sow. NOAA doesn't publish soil-temperature normals, so we list each crop's minimum soil temperature from CSU instead of 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 Centennial

What to plant in Centennial in February

• Start broccoli seeds indoors (Feb 22 – Mar 8)
• Start cabbage seeds indoors (Feb 22 – Mar 8)

What to plant in Centennial in March

• Start cauliflower seeds indoors (Mar 8–22)
• Start eggplant seeds indoors (Mar 22 – Apr 12)
• Start pepper seeds indoors (Mar 29 – Apr 12)
• Start broccoli seeds indoors (Feb 22 – Mar 8)
• Start cabbage seeds indoors (Feb 22 – Mar 8)

What to plant in Centennial in April

• Onions (dry, from sets): plant sets outdoors (Apr 7 – May 3)
• Peas: direct sow outdoors (Apr 7 – May 3)
• Lettuce (leaf): direct sow outdoors (Apr 7 – May 3)
• Broccoli: transplant outdoors (Apr 7 – May 3)
• Cabbage: transplant outdoors (Apr 7 – May 3)
• Kohlrabi: direct sow outdoors (Apr 7 – May 3)
• Green onions: direct sow outdoors (Apr 7 – May 3)
• Radishes: direct sow outdoors (Apr 7 – May 3)
• Spinach: direct sow outdoors (Apr 7 – May 3)
• Turnips: direct sow outdoors (Apr 7 – May 3)
• Potatoes: plant (seed pieces) outdoors (Apr 21 – May 17)
• Carrots: direct sow outdoors (Apr 21 – May 17)
• Cauliflower: transplant outdoors (Apr 21 – May 17)
• Beets: direct sow outdoors (Apr 21 – May 17)
• Swiss chard: direct sow outdoors (Apr 21 – May 17)
• Parsnips: direct sow outdoors (Apr 21 – May 17)
• Start tomato seeds indoors (Apr 27 – May 11)
• Start eggplant seeds indoors (Mar 22 – Apr 12)
• Start pepper seeds indoors (Mar 29 – Apr 12)

What to plant in Centennial in May

• Beans (snap): direct sow outdoors (May 5–17)
• Summer squash: direct sow outdoors (May 5–17)
• Sweet corn: direct sow outdoors (May 5–17)
• Cucumbers: direct sow outdoors (May 5–17)
• Start cabbage seeds indoors for a fall crop (May 13–27)
• Peppers: transplant outdoors (May 19–31)
• Eggplant: transplant outdoors (May 19–31)
• Cantaloupe: direct sow outdoors (May 19–31)
• Watermelon: direct sow outdoors (May 19–31)
• Winter squash: direct sow outdoors (May 19–31)
• Onions (dry, from sets): plant sets outdoors (Apr 7 – May 3)
• Peas: direct sow outdoors (Apr 7 – May 3)
• Lettuce (leaf): direct sow outdoors (Apr 7 – May 3)
• Broccoli: transplant outdoors (Apr 7 – May 3)
• Cabbage: transplant outdoors (Apr 7 – May 3)
• Kohlrabi: direct sow outdoors (Apr 7 – May 3)
• Green onions: direct sow outdoors (Apr 7 – May 3)
• Radishes: direct sow outdoors (Apr 7 – May 3)
• Spinach: direct sow outdoors (Apr 7 – May 3)
• Turnips: direct sow outdoors (Apr 7 – May 3)
• Potatoes: plant (seed pieces) outdoors (Apr 21 – May 17)
• Carrots: direct sow outdoors (Apr 21 – May 17)
• Cauliflower: transplant outdoors (Apr 21 – May 17)
• Beets: direct sow outdoors (Apr 21 – May 17)
• Swiss chard: direct sow outdoors (Apr 21 – May 17)
• Parsnips: direct sow outdoors (Apr 21 – May 17)
• Start tomato seeds indoors (Apr 27 – May 11)

What to plant in Centennial in June

• Start broccoli seeds indoors for a fall crop (Jun 2–16)
• Tomatoes: transplant outdoors (Jun 15)

What to plant in Centennial in July

• Last day to set out cabbage transplants for a fall harvest (by Jul 1)
• Last day to sow beans (snap) for a fall harvest (by Jul 12)
• Last day to sow carrots for a fall harvest (by Jul 16)
• Last day to sow cucumbers for a fall harvest (by Jul 17)
• Last day to sow peas for a fall harvest (by Jul 21)
• Last day to set out broccoli transplants for a fall harvest (by Jul 21)
• Last day to sow summer squash for a fall harvest (by Jul 22)
• Last day to sow lettuce (leaf) for a fall harvest (by Jul 26)
• Last day to sow green onions for a fall harvest (by Jul 26)
• Last day to sow beets for a fall harvest (by Jul 26)
• Last day to sow swiss chard for a fall harvest (by Jul 26)

What to plant in Centennial in August

• Last day to sow kohlrabi for a fall harvest (by Aug 5)
• Last day to sow turnips for a fall harvest (by Aug 5)
• Last day to sow spinach for a fall harvest (by Aug 15)
• Last day to sow radishes for a fall harvest (by Aug 25)

What to plant in Centennial in October

• Plant garlic cloves (Oct 1–14)

Crop-by-crop notes

When to plant tomatoes in Centennial

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 Centennial, the frost rule alone would allow about May 19, but the average nightly low at Denver Centennial Airport isn't above 52°F until Jun 15, so the night rule sets the date at every risk level: about Jun 15. Start seeds indoors Apr 27 – May 11, 5–7 weeks before transplanting on Jun 15. Below 55°F at night, fruit set suffers (CSU). At Denver Centennial Airport, the normal low reaches 55°F on Jun 26. CSU's typical time from transplant to harvest for tomato plants is 65 days. Set out on Jun 15, they would start producing around Aug 19, 50 days before the typical first frost (Oct 8).

When to plant peppers in Centennial

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 19 using the typical date, May 24 as a balanced choice, or May 31 if you go by the safer 10% date. Start seeds indoors Mar 29 – Apr 12, 6–8 weeks before transplanting on May 24. CSU notes that nights under 55°F hurt fruit set. The normal low at Denver Centennial Airport climbs to 55°F on Jun 26. Set out on May 24, pepper plants would start producing around Aug 2, based on CSU's typical 70 days from transplant to harvest. That leaves 67 days before the typical first frost (Oct 8).

When to plant potatoes in Centennial

Semi-hardy crop. Per CSU, potatoes can go in as early as 0–2 weeks before the average last frost: roughly Apr 21 – May 5 in Centennial (typical date) or May 3–17 (safer date). The soil should be at least 45°F.

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

Hardy crop. Per CSU, onions (dry, from sets) 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 Centennial, that works out to roughly Apr 7–21 (typical date) or Apr 19 – May 3 (safer date).

When to plant peas in Centennial

Hardy crop. CSU says peas 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 Centennial, that's roughly Apr 7–21 going by the typical date, or Apr 19 – May 3 going by the safer date. For fall, sow by Jul 21 (Jul 8 to be safe), which is 79 days before the first-frost date.

When to plant lettuce (leaf) in Centennial

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 Centennial, that works out to roughly Apr 7–21 (typical date) or Apr 19 – May 3 (safer date). For a fall crop, sow by Jul 26, or by Jul 13 to be safe. That's 74 days back from the first-frost date.

When to plant carrots in Centennial

Semi-hardy crop. Per CSU, carrots can go in as early as 0–2 weeks before the average last frost: roughly Apr 21 – May 5 in Centennial (typical date) or May 3–17 (safer date). The soil should be at least 40°F. For fall, sow by Jul 16 (Jul 3 to be safe), which is 84 days before the first-frost date.

When to plant beans (snap) in Centennial

Tender crop. Sow beans (snap) around the average last frost, per CSU: about May 5 in Centennial. Waiting until May 17 cuts the chance of a later 32°F night to 1 in 10. Seeds need soil of at least 55°F. For a fall crop, sow by Jul 12, or by Jun 29 to be safe. That's 88 days back from the first-frost date.

When to plant summer squash in Centennial

Tender crop. CSU's timing for summer squash is around the average last frost, which is about May 5 in Centennial. For only a 1-in-10 chance of a later 32°F night, hold off until May 17. Seeds want soil at 60°F or warmer. For fall, sow by Jul 22 (Jul 9 to be safe), which is 78 days before the first-frost date.

When to plant broccoli in Centennial

Hardy crop. CSU says broccoli can go in as early as 2–4 weeks before the average last frost: roughly Apr 7–21 in Centennial using the typical date, or Apr 19 – May 3 using the safer one. Wait until the soil can be worked and is at least 40°F. Set out on Apr 12, broccoli plants would start producing around Jun 16, based on CSU's typical 65 days from transplant to harvest. That leaves 114 days before the typical first frost (Oct 8). Fall broccoli: set transplants out by Jul 21. The date counts back from the typical first frost (Oct 8) by UNL Extension's method, using CSU's 65 days from transplant to harvest. Home-grown transplants need seeds started Jun 2–16 (CSU: 5–7 weeks).

When to plant cabbage in Centennial

Hardy crop. CSU says cabbage 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 Centennial, that's roughly Apr 7–21 going by the typical date, or Apr 19 – May 3 going by the safer date. CSU's typical time from transplant to harvest for cabbage plants is 85 days. Set out on Apr 12, they would start producing around Jul 6, 94 days before the typical first frost (Oct 8). Fall cabbage: set transplants out by Jul 1. The date counts back from the typical first frost (Oct 8) by UNL Extension's method, using CSU's 85 days from transplant to harvest. Home-grown transplants need seeds started May 13–27 (CSU: 5–7 weeks).

When to plant cauliflower in Centennial

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 Centennial, that's roughly Apr 21 – May 5 going by the typical date, or May 3–17 going by the safer date.

When to plant kohlrabi in Centennial

Hardy crop. CSU says kohlrabi can go in as early as 2–4 weeks before the average last frost: roughly Apr 7–21 in Centennial using the typical date, or Apr 19 – May 3 using the safer one. Wait until the soil can be worked and is at least 40°F. For fall, count back 64 days from the first-frost date. That means sowing by Aug 5, or by Jul 23 to be safe.

When to plant green onions in Centennial

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 Centennial, that works out to roughly Apr 7–21 (typical date) or Apr 19 – May 3 (safer date). For a fall crop, sow by Jul 26, or by Jul 13 to be safe. That's 74 days back from the first-frost date.

When to plant radishes in Centennial

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 Centennial, that works out to roughly Apr 7–21 (typical date) or Apr 19 – May 3 (safer date). For a fall crop, sow by Aug 25, or by Aug 12 to be safe. That's 44 days back from the first-frost date.

When to plant spinach in Centennial

Hardy crop. CSU says spinach can go in as early as 2–4 weeks before the average last frost: roughly Apr 7–21 in Centennial using the typical date, or Apr 19 – May 3 using the safer one. Wait until the soil can be worked and is at least 40°F. For fall, count back 54 days from the first-frost date. That means sowing by Aug 15, or by Aug 2 to be safe.

When to plant turnips in Centennial

Hardy crop. Per CSU, turnips 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 Centennial, that works out to roughly Apr 7–21 (typical date) or Apr 19 – May 3 (safer date). For fall, count back 64 days from the first-frost date. That means sowing by Aug 5, or by Jul 23 to be safe.

When to plant beets in Centennial

Semi-hardy crop. CSU allows planting beets as early as 0–2 weeks before the average last frost, in soil at 40°F or warmer. For Centennial, that's roughly Apr 21 – May 5 by the typical date or May 3–17 by the safer date. For a fall crop, sow by Jul 26, or by Jul 13 to be safe. That's 74 days back from the first-frost date.

When to plant swiss chard in Centennial

Semi-hardy crop. CSU allows planting swiss chard as early as 0–2 weeks before the average last frost, in soil at 40°F or warmer. For Centennial, that's roughly Apr 21 – May 5 by the typical date or May 3–17 by the safer date. For fall, sow by Jul 26 (Jul 13 to be safe), which is 74 days before the first-frost date.

When to plant parsnips in Centennial

Semi-hardy crop. Per CSU, parsnips can go in as early as 0–2 weeks before the average last frost: roughly Apr 21 – May 5 in Centennial (typical date) or May 3–17 (safer date). The soil should be at least 35°F.

When to plant sweet corn in Centennial

Tender crop. CSU says to sow sweet corn around the average last frost, about May 5 in Centennial. If you want only a 1-in-10 chance of a later 32°F night, wait until May 17. Seeds need soil of at least 50°F.

When to plant cucumbers in Centennial

Tender crop. CSU says to sow cucumbers around the average last frost, about May 5 in Centennial. If you want only a 1-in-10 chance of a later 32°F night, wait until May 17. Seeds need soil of at least 60°F. For fall, sow by Jul 17 (Jul 4 to be safe), which is 83 days before the first-frost date.

When to plant eggplant in Centennial

Very tender crop. CSU Extension's rule is 2+ weeks after the average last frost, which puts eggplant outside around May 19 (typical date), May 24 (balanced) or May 31 (safer 10% date). Start seeds indoors Mar 22 – Apr 12, 6–9 weeks ahead of transplanting on May 24. Set out on May 24, eggplant plants would start producing around Jul 23, based on CSU's typical 60 days from transplant to harvest. That leaves 77 days before the typical first frost (Oct 8).

When to plant cantaloupe in Centennial

Very tender crop. CSU Extension's rule is to plant cantaloupe at least 2 weeks after the average last frost. That's about May 19 using the typical date, May 24 as a balanced choice, or May 31 if you go by the safer 10% date. Seeds need soil of at least 60°F.

When to plant watermelon in Centennial

Very tender crop. CSU Extension's rule is to plant watermelon at least 2 weeks after the average last frost. That's about May 19 using the typical date, May 24 as a balanced choice, or May 31 if you go by the safer 10% date. Seeds need soil of at least 60°F.

When to plant winter squash in Centennial

Very tender crop. CSU Extension's rule is to plant winter squash at least 2 weeks after the average last frost. That's about May 19 using the typical date, May 24 as a balanced choice, or May 31 if you go by the safer 10% date. Seeds need soil of at least 60°F.

When to plant garlic in Centennial

CSU Extension's Colorado guidance is to plant garlic in early October, before October 15 (Oct 1–14). That's a fixed statewide window, not one computed from frost data. At Denver Centennial Airport, the typical first hard freeze (28°F) is Oct 17, 3 days after the window 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 Centennial?

Sow tomatoes indoors Apr 27 – May 11 and peppers Mar 29 – Apr 12. We work back from a balanced (30%-risk) transplant date using CSU's transplant ages.

When should I plant tomatoes outside in Centennial?

Set tomatoes out about Jun 15. The date is the same at every risk level. CSU's rule of 2+ weeks after the average last frost would allow about May 19 here, but CSU also wants nights above 52°F, and the average nightly low at Denver Centennial Airport isn't above that until Jun 15.

What can I plant in Centennial in the fall?

These sowing deadlines count back from the typical first frost (Oct 8) using UNL Extension's method: peas by Jul 21; lettuce (leaf) by Jul 26; carrots by Jul 16; beans (snap) by Jul 12; summer squash by Jul 22; broccoli by Jul 21 (transplants); cabbage by Jul 1 (transplants); kohlrabi by Aug 5; green onions by Jul 26; radishes by Aug 25; spinach by Aug 15; turnips by Aug 5; beets by Jul 26; swiss chard by Jul 26; cucumbers by Jul 17. Plant garlic Oct 1–14.

When should I plant garlic in Centennial?

Early October, before October 15 (Oct 1–14). That's CSU Extension's guidance for Colorado.

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