When to Plant in Colorado: Vegetable & Flower Planting Calendar
Quick answer
Plant around your local last spring frost: across the 527 Colorado ZIP codes where frost comes in most years, the median is May 9 and the median first fall frost is Oct 5 (nearest NOAA station, 1991–2020). Transplant tomatoes 1–2 weeks after your last frost: Zone 5 areas: May 28 – Jun 4; Zone 6 areas: May 11 – May 18.
Colorado spans USDA hardiness zones 4a–7a on the 2023 USDA map (by ZIP code, via PRISM). For the 527 of its 527 ZIP codes where frost comes in most years, the nearest NOAA station’s median last spring frost (32°F, 1991–2020) is May 9 (middle 80% of ZIP codes: Apr 30 – Jun 12) and the median first fall frost is Oct 5 (Sep 11 – Oct 12). Use this guide to time seed-starting, transplanting and fall planting.
Where these dates come from: every date range is counted from the median (50% probability) 32°F last spring and first fall frost dates in NOAA’s 1991–2020 U.S. Climate Normals for the area shown. The rule under each date, such as “4–6 weeks before last frost,” shows how it was counted. These are averages: in about half of years a frost still comes after the spring date, and elevation, nearby water and microclimate can shift your yard by a week or more. For dates for your exact location, enter your ZIP code in the planner.
How we count planting dates: the weeks before or after frost for each crop come from university extension planting guides: UNH Extension, When to Plant Your Vegetable Garden; Rutgers FS787, Starting Vegetable Seeds Indoors; Virginia Tech 426-331, Home Garden Vegetable Planting Guide; University of Maryland Extension, Vegetable Planting Calendar; and University of Idaho CIS 1209 (marigolds and zinnias). Bulb windows approximate Rutgers’ rule to plant when soil falls below 60°F (FS1220), and garlic follows SDSU, Illinois and Virginia Tech. Temperature notes: UMD (potatoes), UMN (sweet corn), UC ANR (peppers, hardening off), UMN (eggplant), Colorado State (tomatoes) and SDSU (hardening off).
Colorado frost dates by zone area
| Zone areas | Most common nearest NOAA stations | Median last spring frost (32°F) | Median first fall frost (32°F) |
|---|---|---|---|
| Zone 5 (268 ZIP codes) | Greeley Unc, CO, Longmont 2 Ese, CO, Vail, CO | May 21middle 80%: May 3 – Jun 16 | Sep 27middle 80%: Sep 9 – Oct 8 |
| Zone 6 (232 ZIP codes) | Denver Water Dept, CO, Colorado Springs Muni Airport, CO, Denver-Stapleton, CO | May 4middle 80%: Apr 30 – May 25 | Oct 8middle 80%: Sep 27 – Oct 13 |
Source: NOAA National Centers for Environmental Information (NCEI), U.S. Climate Normals 1991–2020, annual/seasonal freeze-date probabilities (32°F, 50% probability). Station-level medians; your yard may differ.
How this table is built: each Colorado ZIP code is matched to its nearest NOAA 1991–2020 freeze-data station (within 60 miles) and grouped by its 2023 USDA hardiness zone; dates are medians across the ZIP codes in each group. Zone groups with fewer than 5% of ZIP codes (19 ZIP codes) are left out of the columns. Some nearest stations are across the state line (Baggs, WY, Carpenter 3N, WY, Cedar Pt, UT, Centennial 1Ne, WY, Chama, NM, Dulce, NM…). For your own ZIP, use the planner.
Colorado vegetable planting calendar
Planting dates for each zone area of Colorado, counted from that area’s median frost dates (shown under each column). Rows run in calendar order. For your exact dates, enter your ZIP.
| Plant, task and rule | Zone 5 areasLast frost May 21 · First frost Sep 27 | Zone 6 areasLast frost May 4 · First frost Oct 8 |
|---|---|---|
| Broccoli · Start indoors8–10 weeks before last frost | Mar 12 – Mar 26 | Feb 23 – Mar 9 |
| Cabbage · Start indoors8–10 weeks before last frost | Mar 12 – Mar 26 | Feb 23 – Mar 9 |
| Kale · Start indoors8–10 weeks before last frost | Mar 12 – Mar 26 | Feb 23 – Mar 9 |
| Tomatoes · Start indoors6–8 weeks before last frost | Mar 26 – Apr 9 | Mar 9 – Mar 23 |
| Peppers · Start indoors6–8 weeks before last frost | Mar 26 – Apr 9 | Mar 9 – Mar 23 |
| Eggplant · Start indoors6–8 weeks before last frost | Mar 26 – Apr 9 | Mar 9 – Mar 23 |
| Peas · Direct sow4–6 weeks before last frost | Apr 9 – Apr 23Harvest (est.) Jun 8 – Jul 12 | Mar 23 – Apr 6Harvest (est.) May 22 – Jun 25 |
| Spinach · Direct sow4–6 weeks before last frost | Apr 9 – Apr 23Harvest (est.) May 24 – Jun 22 | Mar 23 – Apr 6Harvest (est.) May 7 – Jun 5 |
| Basil · Start indoors4–6 weeks before last frost | Apr 9 – Apr 23 | Mar 23 – Apr 6 |
| Radishes · Direct sow2–5 weeks before last frost | Apr 16 – May 7Harvest (est.) May 6 – Jun 6 | Mar 30 – Apr 20Harvest (est.) Apr 19 – May 20 |
| Lettuce · Direct sow2–4 weeks before last frost | Apr 23 – May 7Harvest (est.) Jun 22 – Jul 26 | Apr 6 – Apr 20Harvest (est.) Jun 5 – Jul 9 |
| Onions (sets/transplants) · Plant sets/transplants2–4 weeks before last frost | Apr 23 – May 7Harvest (est.) Jul 17 – Sep 4 | Apr 6 – Apr 20Harvest (est.) Jun 30 – Aug 18 |
| Broccoli · Transplant2–4 weeks before last frost | Apr 23 – May 7Harvest (est.) Jun 12 – Jul 16 | Apr 6 – Apr 20Harvest (est.) May 26 – Jun 29 |
| Cabbage · Transplant2–4 weeks before last frost | Apr 23 – May 7Harvest (est.) Jul 2 – Aug 5 | Apr 6 – Apr 20Harvest (est.) Jun 15 – Jul 19 |
| Kale · Transplant2–4 weeks before last frost | Apr 23 – May 7 | Apr 6 – Apr 20 |
| Marigolds · Start indoors0–3 weeks before last frost (3–4 weeks before setting out; Univ. of Idaho) | Apr 30 – May 21 | Apr 13 – May 4 |
| Zinnias · Start indoors0–3 weeks before last frost (3–4 weeks before setting out; Univ. of Idaho) | Apr 30 – May 21 | Apr 13 – May 4 |
| Potatoes · Plant seed potatoes1–2 weeks before last frost | May 7 – May 14Harvest (est.) Jul 31 – Sep 1 | Apr 20 – Apr 27Harvest (est.) Jul 14 – Aug 15 |
| Marigolds · Direct sow / transplantfrom the last frost to 2 weeks after (Univ. of Idaho) | May 21 – Jun 4 | May 4 – May 18 |
| Zinnias · Direct sow / transplantfrom the last frost to 2 weeks after (Univ. of Idaho) | May 21 – Jun 4 | May 4 – May 18 |
| Tomatoes · Transplant1–2 weeks after last frost | May 28 – Jun 4Harvest (est.) Aug 6 – Sep 2 | May 11 – May 18Harvest (est.) Jul 20 – Aug 16 |
| Beans (bush & pole) · Direct sow1–2 weeks after last frost | May 28 – Jun 4Harvest (est.) Jul 12 – Aug 13 | May 11 – May 18Harvest (est.) Jun 25 – Jul 27 |
| Sweet corn · Direct sow1–2 weeks after last frost | May 28 – Jun 4Harvest (est.) Aug 1 – Sep 2 | May 11 – May 18Harvest (est.) Jul 15 – Aug 16 |
| Cucumbers · Direct sow1–2 weeks after last frost | May 28 – Jun 4Harvest (est.) Jul 7 – Aug 8 | May 11 – May 18Harvest (est.) Jun 20 – Jul 22 |
| Squash · Direct sow1–2 weeks after last frost | May 28 – Jun 4Harvest (est.) Jul 7 – Jul 24 | May 11 – May 18Harvest (est.) Jun 20 – Jul 7 |
| Pumpkins · Direct sow1–3 weeks after last frost | May 28 – Jun 11Harvest (est.) Aug 16 – Sep 19 | May 11 – May 25Harvest (est.) Jul 30 – Sep 2 |
| Basil · Transplant1–2 weeks after last frost | May 28 – Jun 4Harvest (est.) Jul 9 – Jul 16 | May 11 – May 18Harvest (est.) Jun 22 – Jun 29 |
| Peppers · Transplant2–3 weeks after last frost | Jun 4 – Jun 11Harvest (est.) Aug 8 – Aug 25 | May 18 – May 25Harvest (est.) Jul 22 – Aug 8 |
| Eggplant · Transplant2–3 weeks after last frost | Jun 4 – Jun 11Harvest (est.) Aug 13 – Sep 9 | May 18 – May 25Harvest (est.) Jul 27 – Aug 23 |
| Broccoli · Fall transplant10–12 weeks before first fall frost | Jul 5 – Jul 19Harvest (est.) Aug 24 – Sep 27 | Jul 16 – Jul 30Harvest (est.) Sep 4 – Oct 8 |
| Cabbage · Fall transplant10–12 weeks before first fall frost | Jul 5 – Jul 19Harvest (est.) Sep 13 – Oct 17 | Jul 16 – Jul 30Harvest (est.) Sep 24 – Oct 28 |
| Kale · Fall sow8–10 weeks before first fall frost | Jul 19 – Aug 2Harvest (est.) Sep 7 – Oct 11 | Jul 30 – Aug 13Harvest (est.) Sep 18 – Oct 22 |
| Lettuce · Fall sow6–8 weeks before first fall frost | Aug 2 – Aug 16Harvest (est.) Oct 1 – Nov 4 | Aug 13 – Aug 27Harvest (est.) Oct 12 – Nov 15 |
| Spinach · Fall sow4–7 weeks before first fall frost (Virginia Tech) | Aug 9 – Aug 30Harvest (est.) Sep 23 – Oct 29 | Aug 20 – Sep 10Harvest (est.) Oct 4 – Nov 9 |
| Radishes · Fall sow4–6 weeks before first fall frost | Aug 16 – Aug 30Harvest (est.) Sep 5 – Sep 29 | Aug 27 – Sep 10Harvest (est.) Sep 16 – Oct 10 |
| Daffodils · Fall plant bulbs4 weeks before to 2 weeks after first fall frost (our approximation of when soil falls below 60°F; Rutgers) | Aug 30 – Oct 11 | Sep 10 – Oct 22 |
| Tulips · Fall plant bulbs2 weeks before to 4 weeks after first fall frost (our approximation of when soil falls below 60°F; Rutgers) | Sep 13 – Oct 25 | Sep 24 – Nov 5 |
| Garlic · Fall plant cloves2 weeks before to 3 weeks after first fall frost, while the soil is still workable (SDSU, Illinois, Virginia Tech) | Sep 13 – Oct 18Harvest (est.) May 21, 2027 – Jul 15, 2027 | Sep 24 – Oct 29Harvest (est.) Jun 1, 2027 – Jul 26, 2027 |
About the harvest estimates
Each expected harvest window adds the days to harvest from the sources below to the planting window. Days count from sowing seed (or planting seed potatoes, onion sets or garlic cloves) or, where marked, from setting transplants out; “Start indoors” rows have no harvest of their own. Harvest timing varies with variety and weather, and many crops keep producing for weeks after the first picking. For frost-tender crops (tomatoes, peppers, eggplant, beans, sweet corn, cucumbers, squash, pumpkins, basil) the window stops at the first fall frost: harvest may end early at the first fall frost. Flowers and bulbs show no harvest window, and kale has no sourced figure for spring transplants.
Sources: UF/IFAS Extension, Florida Vegetable Gardening Guide (SP103/VH021), Table 1, “Days to Harvest”; University of Maryland Extension, Growing Onions in a Home Garden; University of Maryland Extension, Growing Garlic in a Home Garden; University of Maryland Extension, Growing Basil in a Home Garden.
Growing notes for each crop
- Peas: Tolerates light frost; sow when soil is workable
- Spinach: Fall crop too: sow 4–7 weeks before first fall frost (Virginia Tech)
- Lettuce: Bolts in heat; succession sow; fall crop too
- Radishes: Fast (3–4 weeks); sow again for fall (see Fall sow dates)
- Kale: Fall crop too (see Fall sow dates); frost sweetens leaves
- Onions (sets/transplants): Choose day-length type suited to your latitude
- Potatoes: Soil at least 45°F (UMD); hill as plants grow
- Broccoli: Cool-season; harden off; good fall crop
- Cabbage: Cool-season; harden off; good fall crop
- Tomatoes: Wait for nights reliably above about 52°F (Colorado State)
- Peppers: Need warm soil: about 65°F is optimal for transplanting (UC ANR)
- Eggplant: Transplant after nights stay above 50°F (UMN)
- Beans (bush & pole): Seeds rot in cold, wet soil
- Sweet corn: Soil 60°F+ (UNH, UMN); plant in blocks for pollination
- Cucumbers: Frost-tender; watch for cucumber beetles
- Squash: Frost-tender; watch for squash vine borer
- Pumpkins: For October pumpkins, many sow in late May–June
- Basil: Very cold-sensitive
- Marigolds: Easy warm-season annual
- Zinnias: Easy warm-season annual
- Tulips: Our frost-date window is an approximation of that soil rule. In zone 9, chill bulbs 12–16 weeks first (Clemson)
- Daffodils: Our frost-date window is an approximation of that soil rule; slightly earlier than tulips is fine
- Garlic: Harvest the following early summer
Colorado USDA zone guides: Zone 4 planting guide Zone 5 planting guide Zone 6 planting guide Zone 7 planting guide
How we count planting dates: the weeks before or after frost for each crop come from university extension planting guides: UNH Extension, When to Plant Your Vegetable Garden; Rutgers FS787, Starting Vegetable Seeds Indoors; Virginia Tech 426-331, Home Garden Vegetable Planting Guide; University of Maryland Extension, Vegetable Planting Calendar; and University of Idaho CIS 1209 (marigolds and zinnias). Bulb windows approximate Rutgers’ rule to plant when soil falls below 60°F (FS1220), and garlic follows SDSU, Illinois and Virginia Tech. Temperature notes: UMD (potatoes), UMN (sweet corn), UC ANR (peppers, hardening off), UMN (eggplant), Colorado State (tomatoes) and SDSU (hardening off).
Tips for Colorado gardeners
- Watch soil temperature, not just the calendar — warm-season crops stall in cold soil. An inexpensive soil thermometer helps.
- Harden off transplants over 7–10 days before planting out (UC ANR, SDSU).
- Ask your local Cooperative Extension office about varieties and timing for your county; find it in the USDA NIFA land-grant university directory.
- Keep weeds down early — see our weed identification guide.
Frequently asked questions
When is the last frost in Colorado?
Across the 527 Colorado ZIP codes where frost comes in most years, the median last spring frost (32°F, NOAA 1991–2020) at the nearest station is May 9, and the middle 80% of ZIP codes range from Apr 30 to Jun 12. Check the average for your ZIP code, and remember frost can occur after the average date.
When can I plant tomatoes in Colorado?
Transplant tomatoes outdoors 1–2 weeks after your average last frost, once nights stay above about 52°F (Colorado State). Typical dates: Zone 5 areas: May 28 – Jun 4; Zone 6 areas: May 11 – May 18.
What USDA zone is Colorado?
Colorado spans roughly USDA hardiness zones 4a–7a on the 2023 USDA map (by ZIP code, via PRISM). Hardiness zones describe winter low temperatures, not frost dates.
Other state planting calendars
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