When to Plant in Wyoming: Vegetable & Flower Planting Calendar
Quick answer
Plant around your local last spring frost: across the 178 Wyoming ZIP codes where frost comes in most years, the median is May 22 and the median first fall frost is Sep 23 (nearest NOAA station, 1991–2020). Transplant tomatoes 1–2 weeks after your last frost: Zone 4 areas: Jun 1 – Jun 8; Zone 5 areas: May 29 – Jun 5.
Wyoming spans USDA hardiness zones 4a–5b on the 2023 USDA map (by ZIP code, via PRISM). For the 178 of its 178 ZIP codes where frost comes in most years, the nearest NOAA station’s median last spring frost (32°F, 1991–2020) is May 22 (middle 80% of ZIP codes: May 12 – Jun 14) and the median first fall frost is Sep 23 (Sep 1 – Oct 1). 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).
Wyoming 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 4 (50 ZIP codes) | Afton, WY, Burris, WY, La Barge, WY | May 25middle 80%: May 12 – Jun 20 | Sep 18middle 80%: Sep 1 – Oct 1 |
| Zone 5 (128 ZIP codes) | Afton, WY, Mtn View, WY, Diversion Dam, WY | May 22middle 80%: May 12 – Jun 14 | Sep 23middle 80%: Sep 9 – Oct 1 |
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 Wyoming 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. Some nearest stations are across the state line (Bear Ridge, SD, Biddle 8 Sw, MT, Lifton Pumping Stn, ID, Manila, UT, Randolph, UT, Rustic 9Wsw, CO…). For your own ZIP, use the planner.
Wyoming vegetable planting calendar
Planting dates for each zone area of Wyoming, 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 4 areasLast frost May 25 · First frost Sep 18 | Zone 5 areasLast frost May 22 · First frost Sep 23 |
|---|---|---|
| Broccoli · Start indoors8–10 weeks before last frost | Mar 16 – Mar 30 | Mar 13 – Mar 27 |
| Cabbage · Start indoors8–10 weeks before last frost | Mar 16 – Mar 30 | Mar 13 – Mar 27 |
| Kale · Start indoors8–10 weeks before last frost | Mar 16 – Mar 30 | Mar 13 – Mar 27 |
| Tomatoes · Start indoors6–8 weeks before last frost | Mar 30 – Apr 13 | Mar 27 – Apr 10 |
| Peppers · Start indoors6–8 weeks before last frost | Mar 30 – Apr 13 | Mar 27 – Apr 10 |
| Eggplant · Start indoors6–8 weeks before last frost | Mar 30 – Apr 13 | Mar 27 – Apr 10 |
| Peas · Direct sow4–6 weeks before last frost | Apr 13 – Apr 27Harvest (est.) Jun 12 – Jul 16 | Apr 10 – Apr 24Harvest (est.) Jun 9 – Jul 13 |
| Spinach · Direct sow4–6 weeks before last frost | Apr 13 – Apr 27Harvest (est.) May 28 – Jun 26 | Apr 10 – Apr 24Harvest (est.) May 25 – Jun 23 |
| Basil · Start indoors4–6 weeks before last frost | Apr 13 – Apr 27 | Apr 10 – Apr 24 |
| Radishes · Direct sow2–5 weeks before last frost | Apr 20 – May 11Harvest (est.) May 10 – Jun 10 | Apr 17 – May 8Harvest (est.) May 7 – Jun 7 |
| Lettuce · Direct sow2–4 weeks before last frost | Apr 27 – May 11Harvest (est.) Jun 26 – Jul 30 | Apr 24 – May 8Harvest (est.) Jun 23 – Jul 27 |
| Onions (sets/transplants) · Plant sets/transplants2–4 weeks before last frost | Apr 27 – May 11Harvest (est.) Jul 21 – Sep 8 | Apr 24 – May 8Harvest (est.) Jul 18 – Sep 5 |
| Broccoli · Transplant2–4 weeks before last frost | Apr 27 – May 11Harvest (est.) Jun 16 – Jul 20 | Apr 24 – May 8Harvest (est.) Jun 13 – Jul 17 |
| Cabbage · Transplant2–4 weeks before last frost | Apr 27 – May 11Harvest (est.) Jul 6 – Aug 9 | Apr 24 – May 8Harvest (est.) Jul 3 – Aug 6 |
| Kale · Transplant2–4 weeks before last frost | Apr 27 – May 11 | Apr 24 – May 8 |
| Marigolds · Start indoors0–3 weeks before last frost (3–4 weeks before setting out; Univ. of Idaho) | May 4 – May 25 | May 1 – May 22 |
| Zinnias · Start indoors0–3 weeks before last frost (3–4 weeks before setting out; Univ. of Idaho) | May 4 – May 25 | May 1 – May 22 |
| Potatoes · Plant seed potatoes1–2 weeks before last frost | May 11 – May 18Harvest (est.) Aug 4 – Sep 5 | May 8 – May 15Harvest (est.) Aug 1 – Sep 2 |
| Marigolds · Direct sow / transplantfrom the last frost to 2 weeks after (Univ. of Idaho) | May 25 – Jun 8 | May 22 – Jun 5 |
| Zinnias · Direct sow / transplantfrom the last frost to 2 weeks after (Univ. of Idaho) | May 25 – Jun 8 | May 22 – Jun 5 |
| Tomatoes · Transplant1–2 weeks after last frost | Jun 1 – Jun 8Harvest (est.) Aug 10 – Sep 6 | May 29 – Jun 5Harvest (est.) Aug 7 – Sep 3 |
| Beans (bush & pole) · Direct sow1–2 weeks after last frost | Jun 1 – Jun 8Harvest (est.) Jul 16 – Aug 17 | May 29 – Jun 5Harvest (est.) Jul 13 – Aug 14 |
| Sweet corn · Direct sow1–2 weeks after last frost | Jun 1 – Jun 8Harvest (est.) Aug 5 – Sep 6 | May 29 – Jun 5Harvest (est.) Aug 2 – Sep 3 |
| Cucumbers · Direct sow1–2 weeks after last frost | Jun 1 – Jun 8Harvest (est.) Jul 11 – Aug 12 | May 29 – Jun 5Harvest (est.) Jul 8 – Aug 9 |
| Squash · Direct sow1–2 weeks after last frost | Jun 1 – Jun 8Harvest (est.) Jul 11 – Jul 28 | May 29 – Jun 5Harvest (est.) Jul 8 – Jul 25 |
| Pumpkins · Direct sow1–3 weeks after last frost | Jun 1 – Jun 15Harvest (est.) Aug 20 – Sep 18 (first fall frost) | May 29 – Jun 12Harvest (est.) Aug 17 – Sep 20 |
| Basil · Transplant1–2 weeks after last frost | Jun 1 – Jun 8Harvest (est.) Jul 13 – Jul 20 | May 29 – Jun 5Harvest (est.) Jul 10 – Jul 17 |
| Peppers · Transplant2–3 weeks after last frost | Jun 8 – Jun 15Harvest (est.) Aug 12 – Aug 29 | Jun 5 – Jun 12Harvest (est.) Aug 9 – Aug 26 |
| Eggplant · Transplant2–3 weeks after last frost | Jun 8 – Jun 15Harvest (est.) Aug 17 – Sep 13 | Jun 5 – Jun 12Harvest (est.) Aug 14 – Sep 10 |
| Broccoli · Fall transplant10–12 weeks before first fall frost | Jun 26 – Jul 10Harvest (est.) Aug 15 – Sep 18 | Jul 1 – Jul 15Harvest (est.) Aug 20 – Sep 23 |
| Cabbage · Fall transplant10–12 weeks before first fall frost | Jun 26 – Jul 10Harvest (est.) Sep 4 – Oct 8 | Jul 1 – Jul 15Harvest (est.) Sep 9 – Oct 13 |
| Kale · Fall sow8–10 weeks before first fall frost | Jul 10 – Jul 24Harvest (est.) Aug 29 – Oct 2 | Jul 15 – Jul 29Harvest (est.) Sep 3 – Oct 7 |
| Lettuce · Fall sow6–8 weeks before first fall frost | Jul 24 – Aug 7Harvest (est.) Sep 22 – Oct 26 | Jul 29 – Aug 12Harvest (est.) Sep 27 – Oct 31 |
| Spinach · Fall sow4–7 weeks before first fall frost (Virginia Tech) | Jul 31 – Aug 21Harvest (est.) Sep 14 – Oct 20 | Aug 5 – Aug 26Harvest (est.) Sep 19 – Oct 25 |
| Radishes · Fall sow4–6 weeks before first fall frost | Aug 7 – Aug 21Harvest (est.) Aug 27 – Sep 20 | Aug 12 – Aug 26Harvest (est.) Sep 1 – Sep 25 |
| Daffodils · Fall plant bulbs4 weeks before to 2 weeks after first fall frost (our approximation of when soil falls below 60°F; Rutgers) | Aug 21 – Oct 2 | Aug 26 – Oct 7 |
| Tulips · Fall plant bulbs2 weeks before to 4 weeks after first fall frost (our approximation of when soil falls below 60°F; Rutgers) | Sep 4 – Oct 16 | Sep 9 – Oct 21 |
| Garlic · Fall plant cloves2 weeks before to 3 weeks after first fall frost, while the soil is still workable (SDSU, Illinois, Virginia Tech) | Sep 4 – Oct 9Harvest (est.) May 12, 2027 – Jul 6, 2027 | Sep 9 – Oct 14Harvest (est.) May 17, 2027 – Jul 11, 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
Wyoming USDA zone guides: Zone 4 planting guide Zone 5 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 Wyoming 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 Wyoming?
Across the 178 Wyoming ZIP codes where frost comes in most years, the median last spring frost (32°F, NOAA 1991–2020) at the nearest station is May 22, and the middle 80% of ZIP codes range from May 12 to Jun 14. Check the average for your ZIP code, and remember frost can occur after the average date.
When can I plant tomatoes in Wyoming?
Transplant tomatoes outdoors 1–2 weeks after your average last frost, once nights stay above about 52°F (Colorado State). Typical dates: Zone 4 areas: Jun 1 – Jun 8; Zone 5 areas: May 29 – Jun 5.
What USDA zone is Wyoming?
Wyoming spans roughly USDA hardiness zones 4a–5b 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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