Littleton, CO Vegetable Planting Calendar

What to plant now in Littleton

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 2, 50% risk), balanced = May 8 (30%), safe = May 17 (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 Littleton

What to plant in Littleton in February

• Start broccoli seeds indoors (Feb 20 – Mar 6)
• Start cabbage seeds indoors (Feb 20 – Mar 6)

What to plant in Littleton in March

• Start cauliflower seeds indoors (Mar 6–20)
• Start eggplant seeds indoors (Mar 20 – Apr 10)
• Start pepper seeds indoors (Mar 27 – Apr 10)
• Start broccoli seeds indoors (Feb 20 – Mar 6)
• Start cabbage seeds indoors (Feb 20 – Mar 6)

What to plant in Littleton in April

• Onions (dry, from sets): plant sets outdoors (Apr 4 – May 3)
• Peas: direct sow outdoors (Apr 4 – May 3)
• Lettuce (leaf): direct sow outdoors (Apr 4 – May 3)
• Broccoli: transplant outdoors (Apr 4 – May 3)
• Cabbage: transplant outdoors (Apr 4 – May 3)
• Kohlrabi: direct sow outdoors (Apr 4 – May 3)
• Green onions: direct sow outdoors (Apr 4 – May 3)
• Radishes: direct sow outdoors (Apr 4 – May 3)
• Spinach: direct sow outdoors (Apr 4 – May 3)
• Turnips: direct sow outdoors (Apr 4 – May 3)
• Potatoes: plant (seed pieces) outdoors (Apr 18 – May 17)
• Carrots: direct sow outdoors (Apr 18 – May 17)
• Cauliflower: transplant outdoors (Apr 18 – May 17)
• Beets: direct sow outdoors (Apr 18 – May 17)
• Swiss chard: direct sow outdoors (Apr 18 – May 17)
• Parsnips: direct sow outdoors (Apr 18 – May 17)
• Start tomato seeds indoors (Apr 23 – May 7)
• Start eggplant seeds indoors (Mar 20 – Apr 10)
• Start pepper seeds indoors (Mar 27 – Apr 10)

What to plant in Littleton in May

• Beans (snap): direct sow outdoors (May 2–17)
• Summer squash: direct sow outdoors (May 2–17)
• Sweet corn: direct sow outdoors (May 2–17)
• Cucumbers: direct sow outdoors (May 2–17)
• Peppers: transplant outdoors (May 16–31)
• Start cabbage seeds indoors for a fall crop (May 16–30)
• Eggplant: transplant outdoors (May 16–31)
• Cantaloupe: direct sow outdoors (May 16–31)
• Watermelon: direct sow outdoors (May 16–31)
• Winter squash: direct sow outdoors (May 16–31)
• Onions (dry, from sets): plant sets outdoors (Apr 4 – May 3)
• Peas: direct sow outdoors (Apr 4 – May 3)
• Lettuce (leaf): direct sow outdoors (Apr 4 – May 3)
• Broccoli: transplant outdoors (Apr 4 – May 3)
• Cabbage: transplant outdoors (Apr 4 – May 3)
• Kohlrabi: direct sow outdoors (Apr 4 – May 3)
• Green onions: direct sow outdoors (Apr 4 – May 3)
• Radishes: direct sow outdoors (Apr 4 – May 3)
• Spinach: direct sow outdoors (Apr 4 – May 3)
• Turnips: direct sow outdoors (Apr 4 – May 3)
• Potatoes: plant (seed pieces) outdoors (Apr 18 – May 17)
• Carrots: direct sow outdoors (Apr 18 – May 17)
• Cauliflower: transplant outdoors (Apr 18 – May 17)
• Beets: direct sow outdoors (Apr 18 – May 17)
• Swiss chard: direct sow outdoors (Apr 18 – May 17)
• Parsnips: direct sow outdoors (Apr 18 – May 17)
• Start tomato seeds indoors (Apr 23 – May 7)

What to plant in Littleton in June

• Start broccoli seeds indoors for a fall crop (Jun 5–19)
• Tomatoes: transplant outdoors (Jun 11)

What to plant in Littleton in July

• Last day to set out cabbage transplants for a fall harvest (by Jul 4)
• Last day to sow beans (snap) for a fall harvest (by Jul 15)
• Last day to sow carrots for a fall harvest (by Jul 19)
• Last day to sow cucumbers for a fall harvest (by Jul 20)
• Last day to sow peas for a fall harvest (by Jul 24)
• Last day to set out broccoli transplants for a fall harvest (by Jul 24)
• Last day to sow summer squash for a fall harvest (by Jul 25)
• Last day to sow lettuce (leaf) for a fall harvest (by Jul 29)
• Last day to sow green onions for a fall harvest (by Jul 29)
• Last day to sow beets for a fall harvest (by Jul 29)
• Last day to sow swiss chard for a fall harvest (by Jul 29)

What to plant in Littleton in August

• Last day to sow kohlrabi for a fall harvest (by Aug 8)
• Last day to sow turnips for a fall harvest (by Aug 8)
• Last day to sow spinach for a fall harvest (by Aug 18)
• Last day to sow radishes for a fall harvest (by Aug 28)

What to plant in Littleton in October

• Plant garlic cloves (Oct 1–14)

Crop-by-crop notes

When to plant tomatoes in Littleton

Very tender crop. Set tomatoes out about Jun 11, whichever risk level you go by. That date comes from CSU Extension's night rule (nights above 52°F): the average nightly low at Marston Filter Plant first rises above 52°F on Jun 11. CSU's other rule, at least 2 weeks after the average last frost, would allow about May 16 in Littleton. Sow seeds indoors Apr 23 – May 7, 5–7 weeks before transplanting on Jun 11. CSU notes that nights under 55°F hurt fruit set. The normal low at Marston Filter Plant climbs to 55°F on Jun 22. CSU's typical time from transplant to harvest for tomato plants is 65 days. Set out on Jun 11, they would start producing around Aug 15, 57 days before the typical first frost (Oct 11).

When to plant peppers in Littleton

Very tender crop. Following CSU Extension's rule (2+ weeks after the average last frost), set peppers out around May 16 with the typical date, May 22 for a balanced choice, or May 31 with the safer 10% date. Sow seeds indoors Mar 27 – Apr 10, 6–8 weeks before transplanting on May 22. CSU notes that nights under 55°F hurt fruit set. The normal low at Marston Filter Plant climbs to 55°F on Jun 22. CSU's typical time from transplant to harvest for pepper plants is 70 days. Set out on May 22, they would start producing around Jul 31, 72 days before the typical first frost (Oct 11).

When to plant potatoes in Littleton

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 Littleton, that's roughly Apr 18 – May 2 going by the typical date, or May 3–17 going by the safer date.

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

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 Littleton, that's roughly Apr 4–18 going by the typical date, or Apr 19 – May 3 going by the safer date.

When to plant peas in Littleton

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 Littleton, that's roughly Apr 4–18 going by the typical date, or Apr 19 – May 3 going by the safer date. For fall, count back 79 days from the first-frost date. That means sowing by Jul 24, or by Jul 10 to be safe.

When to plant lettuce (leaf) in Littleton

Hardy crop. CSU says lettuce (leaf) can go in as early as 2–4 weeks before the average last frost: roughly Apr 4–18 in Littleton using the typical date, or Apr 19 – May 3 using the safer one. Wait until the soil can be worked and is at least 35°F. For fall, sow by Jul 29 (Jul 15 to be safe), which is 74 days before the first-frost date.

When to plant carrots in Littleton

Semi-hardy crop. CSU allows planting carrots as early as 0–2 weeks before the average last frost, in soil at 40°F or warmer. For Littleton, that's roughly Apr 18 – May 2 by the typical date or May 3–17 by the safer date. For fall, sow by Jul 19 (Jul 5 to be safe), which is 84 days before the first-frost date.

When to plant beans (snap) in Littleton

Tender crop. CSU's timing for beans (snap) is around the average last frost, which is about May 2 in Littleton. For only a 1-in-10 chance of a later 32°F night, hold off until May 17. Seeds want soil at 55°F or warmer. For fall, sow by Jul 15 (Jul 1 to be safe), which is 88 days before the first-frost date.

When to plant summer squash in Littleton

Tender crop. CSU's timing for summer squash is around the average last frost, which is about May 2 in Littleton. 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 25 (Jul 11 to be safe), which is 78 days before the first-frost date.

When to plant broccoli in Littleton

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 Littleton, that's roughly Apr 4–18 going by the typical date, or Apr 19 – May 3 going by the safer date. CSU's typical time from transplant to harvest for broccoli plants is 65 days. Set out on Apr 10, they would start producing around Jun 14, 119 days before the typical first frost (Oct 11). For a fall crop, set broccoli transplants out by Jul 24. That's UNL Extension's count-back from the typical first frost (Oct 11), using CSU's 65 days from transplant to harvest. If you grow your own transplants, start seeds Jun 5–19 (CSU: 5–7 weeks to transplant size).

When to plant cabbage in Littleton

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 Littleton, that's roughly Apr 4–18 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 10, they would start producing around Jul 4, 99 days before the typical first frost (Oct 11). Fall cabbage: set transplants out by Jul 4. The date counts back from the typical first frost (Oct 11) by UNL Extension's method, using CSU's 85 days from transplant to harvest. Home-grown transplants need seeds started May 16–30 (CSU: 5–7 weeks).

When to plant cauliflower in Littleton

Semi-hardy crop. Per CSU, cauliflower can go in as early as 0–2 weeks before the average last frost: roughly Apr 18 – May 2 in Littleton (typical date) or May 3–17 (safer date). The soil should be at least 40°F.

When to plant kohlrabi in Littleton

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 Littleton, that works out to roughly Apr 4–18 (typical date) or Apr 19 – May 3 (safer date). For fall, sow by Aug 8 (Jul 25 to be safe), which is 64 days before the first-frost date.

When to plant green onions in Littleton

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 Littleton, that works out to roughly Apr 4–18 (typical date) or Apr 19 – May 3 (safer date). For fall, count back 74 days from the first-frost date. That means sowing by Jul 29, or by Jul 15 to be safe.

When to plant radishes in Littleton

Hardy crop. CSU says radishes 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 Littleton, that's roughly Apr 4–18 going by the typical date, or Apr 19 – May 3 going by the safer date. For a fall crop, sow by Aug 28, or by Aug 14 to be safe. That's 44 days back from the first-frost date.

When to plant spinach in Littleton

Hardy crop. CSU says spinach can go in as early as 2–4 weeks before the average last frost: roughly Apr 4–18 in Littleton 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 18, or by Aug 4 to be safe.

When to plant turnips in Littleton

Hardy crop. CSU says turnips can go in as early as 2–4 weeks before the average last frost: roughly Apr 4–18 in Littleton 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 a fall crop, sow by Aug 8, or by Jul 25 to be safe. That's 64 days back from the first-frost date.

When to plant beets in Littleton

Semi-hardy crop. Per CSU, beets can go in as early as 0–2 weeks before the average last frost: roughly Apr 18 – May 2 in Littleton (typical date) or May 3–17 (safer date). The soil should be at least 40°F. For fall, count back 74 days from the first-frost date. That means sowing by Jul 29, or by Jul 15 to be safe.

When to plant swiss chard in Littleton

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 Littleton, that's roughly Apr 18 – May 2 going by the typical date, or May 3–17 going by the safer date. For a fall crop, sow by Jul 29, or by Jul 15 to be safe. That's 74 days back from the first-frost date.

When to plant parsnips in Littleton

Semi-hardy crop. Per CSU, parsnips can go in as early as 0–2 weeks before the average last frost: roughly Apr 18 – May 2 in Littleton (typical date) or May 3–17 (safer date). The soil should be at least 35°F.

When to plant sweet corn in Littleton

Tender crop. Sow sweet corn around the average last frost, per CSU: about May 2 in Littleton. Waiting until May 17 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 Littleton

Tender crop. CSU's timing for cucumbers is around the average last frost, which is about May 2 in Littleton. 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 20 (Jul 6 to be safe), which is 83 days before the first-frost date.

When to plant eggplant in Littleton

Very tender crop. CSU Extension's rule is to set eggplant out at least 2 weeks after the average last frost. That's about May 16 using the typical date, May 22 as a balanced choice, or May 31 if you go by the safer 10% date. Start seeds indoors Mar 20 – Apr 10, 6–9 weeks before transplanting on May 22. Set out on May 22, eggplant plants would start producing around Jul 21, based on CSU's typical 60 days from transplant to harvest. That leaves 82 days before the typical first frost (Oct 11).

When to plant cantaloupe in Littleton

Very tender crop. CSU Extension's rule is to plant cantaloupe at least 2 weeks after the average last frost. That's about May 16 using the typical date, May 22 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 Littleton

Very tender crop. Following CSU Extension's rule of 2+ weeks after the average last frost, plant watermelon around May 16 at the earliest, May 22 as a balanced choice, or May 31 to be safe. CSU's minimum soil temperature is 60°F.

When to plant winter squash in Littleton

Very tender crop. Following CSU Extension's rule of 2+ weeks after the average last frost, plant winter squash around May 16 at the earliest, May 22 as a balanced choice, or May 31 to be safe. CSU's minimum soil temperature is 60°F.

When to plant garlic in Littleton

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 Marston Filter Plant, the typical first hard freeze (28°F) is Oct 21, 7 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 Littleton?

Tomatoes: Apr 23 – May 7. Peppers: Mar 27 – Apr 10. Both windows count back from a balanced (30%-risk) transplant date using CSU's transplant ages.

When should I plant tomatoes outside in Littleton?

About Jun 11 at every risk level, because the night rule decides it. CSU wants nights above 52°F at transplant, and the average nightly low at Marston Filter Plant first rises above 52°F on Jun 11. CSU's frost rule (2+ weeks after the average last frost) would allow about May 16 here.

What can I plant in Littleton in the fall?

Based on UNL Extension's count-back from the typical first frost (Oct 11), sow peas by Jul 24; lettuce (leaf) by Jul 29; carrots by Jul 19; beans (snap) by Jul 15; summer squash by Jul 25; broccoli by Jul 24 (transplants); cabbage by Jul 4 (transplants); kohlrabi by Aug 8; green onions by Jul 29; radishes by Aug 28; spinach by Aug 18; turnips by Aug 8; beets by Jul 29; swiss chard by Jul 29; cucumbers by Jul 20. Garlic goes in Oct 1–14.

When should I plant garlic in Littleton?

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

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