When to Plant in Idaho: Vegetable & Flower Planting Calendar
Quick answer
Plant around your local last spring frost: across the 280 Idaho ZIP codes where frost comes in most years, the median is May 15 and the median first fall frost is Sep 28 (nearest NOAA station, 1991–2020). Transplant tomatoes 1–2 weeks after your last frost: Zone 5 areas: May 30 – Jun 6; Zone 6 areas: May 22 – May 29; Zone 7 areas: May 6 – May 13.
Idaho spans USDA hardiness zones 4a–7b on the 2023 USDA map (by ZIP code, via PRISM). For the 280 of its 280 ZIP codes where frost comes in most years, the nearest NOAA station’s median last spring frost (32°F, 1991–2020) is May 15 (middle 80% of ZIP codes: Apr 24 – Jun 12) and the median first fall frost is Sep 28 (Sep 9 – Oct 17). 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).
Idaho 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 (78 ZIP codes) | Bern, ID, Aberdeen Exp Stn, ID, Lifton Pumping Stn, ID | May 23middle 80%: May 9 – Jun 16 | Sep 20middle 80%: Sep 6 – Oct 2 |
| Zone 6 (132 ZIP codes) | Potlatch 3 Nne, ID, Coeur D'Alene, ID, Bayview Model Basin, ID | May 15middle 80%: Apr 30 – Jun 3 | Sep 28middle 80%: Sep 11 – Oct 13 |
| Zone 7 (63 ZIP codes) | Boise Air Terminal, ID, Dworshak Fish Hatchery, ID, Nampa Sugar Factory, ID | Apr 29middle 80%: Apr 20 – May 23 | Oct 13middle 80%: Sep 28 – Oct 21 |
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 Idaho 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 (4 ZIP codes) are left out of the columns. Some nearest stations are across the state line (Afton, WY, Alta 1 Nnw, WY, Bear Lake Sp, UT, Hebgen Dam, MT, Lima, MT, Malheur Branch Exp Stn, OR…). For your own ZIP, use the planner.
Idaho vegetable planting calendar
Planting dates for each zone area of Idaho, 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 23 · First frost Sep 20 | Zone 6 areasLast frost May 15 · First frost Sep 28 | Zone 7 areasLast frost Apr 29 · First frost Oct 13 |
|---|---|---|---|
| Broccoli · Start indoors8–10 weeks before last frost | Mar 14 – Mar 28 | Mar 6 – Mar 20 | Feb 18 – Mar 4 |
| Cabbage · Start indoors8–10 weeks before last frost | Mar 14 – Mar 28 | Mar 6 – Mar 20 | Feb 18 – Mar 4 |
| Kale · Start indoors8–10 weeks before last frost | Mar 14 – Mar 28 | Mar 6 – Mar 20 | Feb 18 – Mar 4 |
| Tomatoes · Start indoors6–8 weeks before last frost | Mar 28 – Apr 11 | Mar 20 – Apr 3 | Mar 4 – Mar 18 |
| Peppers · Start indoors6–8 weeks before last frost | Mar 28 – Apr 11 | Mar 20 – Apr 3 | Mar 4 – Mar 18 |
| Eggplant · Start indoors6–8 weeks before last frost | Mar 28 – Apr 11 | Mar 20 – Apr 3 | Mar 4 – Mar 18 |
| Peas · Direct sow4–6 weeks before last frost | Apr 11 – Apr 25Harvest (est.) Jun 10 – Jul 14 | Apr 3 – Apr 17Harvest (est.) Jun 2 – Jul 6 | Mar 18 – Apr 1Harvest (est.) May 17 – Jun 20 |
| Spinach · Direct sow4–6 weeks before last frost | Apr 11 – Apr 25Harvest (est.) May 26 – Jun 24 | Apr 3 – Apr 17Harvest (est.) May 18 – Jun 16 | Mar 18 – Apr 1Harvest (est.) May 2 – May 31 |
| Basil · Start indoors4–6 weeks before last frost | Apr 11 – Apr 25 | Apr 3 – Apr 17 | Mar 18 – Apr 1 |
| Radishes · Direct sow2–5 weeks before last frost | Apr 18 – May 9Harvest (est.) May 8 – Jun 8 | Apr 10 – May 1Harvest (est.) Apr 30 – May 31 | Mar 25 – Apr 15Harvest (est.) Apr 14 – May 15 |
| Lettuce · Direct sow2–4 weeks before last frost | Apr 25 – May 9Harvest (est.) Jun 24 – Jul 28 | Apr 17 – May 1Harvest (est.) Jun 16 – Jul 20 | Apr 1 – Apr 15Harvest (est.) May 31 – Jul 4 |
| Onions (sets/transplants) · Plant sets/transplants2–4 weeks before last frost | Apr 25 – May 9Harvest (est.) Jul 19 – Sep 6 | Apr 17 – May 1Harvest (est.) Jul 11 – Aug 29 | Apr 1 – Apr 15Harvest (est.) Jun 25 – Aug 13 |
| Broccoli · Transplant2–4 weeks before last frost | Apr 25 – May 9Harvest (est.) Jun 14 – Jul 18 | Apr 17 – May 1Harvest (est.) Jun 6 – Jul 10 | Apr 1 – Apr 15Harvest (est.) May 21 – Jun 24 |
| Cabbage · Transplant2–4 weeks before last frost | Apr 25 – May 9Harvest (est.) Jul 4 – Aug 7 | Apr 17 – May 1Harvest (est.) Jun 26 – Jul 30 | Apr 1 – Apr 15Harvest (est.) Jun 10 – Jul 14 |
| Kale · Transplant2–4 weeks before last frost | Apr 25 – May 9 | Apr 17 – May 1 | Apr 1 – Apr 15 |
| Marigolds · Start indoors0–3 weeks before last frost (3–4 weeks before setting out; Univ. of Idaho) | May 2 – May 23 | Apr 24 – May 15 | Apr 8 – Apr 29 |
| Zinnias · Start indoors0–3 weeks before last frost (3–4 weeks before setting out; Univ. of Idaho) | May 2 – May 23 | Apr 24 – May 15 | Apr 8 – Apr 29 |
| Potatoes · Plant seed potatoes1–2 weeks before last frost | May 9 – May 16Harvest (est.) Aug 2 – Sep 3 | May 1 – May 8Harvest (est.) Jul 25 – Aug 26 | Apr 15 – Apr 22Harvest (est.) Jul 9 – Aug 10 |
| Marigolds · Direct sow / transplantfrom the last frost to 2 weeks after (Univ. of Idaho) | May 23 – Jun 6 | May 15 – May 29 | Apr 29 – May 13 |
| Zinnias · Direct sow / transplantfrom the last frost to 2 weeks after (Univ. of Idaho) | May 23 – Jun 6 | May 15 – May 29 | Apr 29 – May 13 |
| Tomatoes · Transplant1–2 weeks after last frost | May 30 – Jun 6Harvest (est.) Aug 8 – Sep 4 | May 22 – May 29Harvest (est.) Jul 31 – Aug 27 | May 6 – May 13Harvest (est.) Jul 15 – Aug 11 |
| Beans (bush & pole) · Direct sow1–2 weeks after last frost | May 30 – Jun 6Harvest (est.) Jul 14 – Aug 15 | May 22 – May 29Harvest (est.) Jul 6 – Aug 7 | May 6 – May 13Harvest (est.) Jun 20 – Jul 22 |
| Sweet corn · Direct sow1–2 weeks after last frost | May 30 – Jun 6Harvest (est.) Aug 3 – Sep 4 | May 22 – May 29Harvest (est.) Jul 26 – Aug 27 | May 6 – May 13Harvest (est.) Jul 10 – Aug 11 |
| Cucumbers · Direct sow1–2 weeks after last frost | May 30 – Jun 6Harvest (est.) Jul 9 – Aug 10 | May 22 – May 29Harvest (est.) Jul 1 – Aug 2 | May 6 – May 13Harvest (est.) Jun 15 – Jul 17 |
| Squash · Direct sow1–2 weeks after last frost | May 30 – Jun 6Harvest (est.) Jul 9 – Jul 26 | May 22 – May 29Harvest (est.) Jul 1 – Jul 18 | May 6 – May 13Harvest (est.) Jun 15 – Jul 2 |
| Pumpkins · Direct sow1–3 weeks after last frost | May 30 – Jun 13Harvest (est.) Aug 18 – Sep 20 (first fall frost) | May 22 – Jun 5Harvest (est.) Aug 10 – Sep 13 | May 6 – May 20Harvest (est.) Jul 25 – Aug 28 |
| Basil · Transplant1–2 weeks after last frost | May 30 – Jun 6Harvest (est.) Jul 11 – Jul 18 | May 22 – May 29Harvest (est.) Jul 3 – Jul 10 | May 6 – May 13Harvest (est.) Jun 17 – Jun 24 |
| Peppers · Transplant2–3 weeks after last frost | Jun 6 – Jun 13Harvest (est.) Aug 10 – Aug 27 | May 29 – Jun 5Harvest (est.) Aug 2 – Aug 19 | May 13 – May 20Harvest (est.) Jul 17 – Aug 3 |
| Eggplant · Transplant2–3 weeks after last frost | Jun 6 – Jun 13Harvest (est.) Aug 15 – Sep 11 | May 29 – Jun 5Harvest (est.) Aug 7 – Sep 3 | May 13 – May 20Harvest (est.) Jul 22 – Aug 18 |
| Broccoli · Fall transplant10–12 weeks before first fall frost | Jun 28 – Jul 12Harvest (est.) Aug 17 – Sep 20 | Jul 6 – Jul 20Harvest (est.) Aug 25 – Sep 28 | Jul 21 – Aug 4Harvest (est.) Sep 9 – Oct 13 |
| Cabbage · Fall transplant10–12 weeks before first fall frost | Jun 28 – Jul 12Harvest (est.) Sep 6 – Oct 10 | Jul 6 – Jul 20Harvest (est.) Sep 14 – Oct 18 | Jul 21 – Aug 4Harvest (est.) Sep 29 – Nov 2 |
| Kale · Fall sow8–10 weeks before first fall frost | Jul 12 – Jul 26Harvest (est.) Aug 31 – Oct 4 | Jul 20 – Aug 3Harvest (est.) Sep 8 – Oct 12 | Aug 4 – Aug 18Harvest (est.) Sep 23 – Oct 27 |
| Lettuce · Fall sow6–8 weeks before first fall frost | Jul 26 – Aug 9Harvest (est.) Sep 24 – Oct 28 | Aug 3 – Aug 17Harvest (est.) Oct 2 – Nov 5 | Aug 18 – Sep 1Harvest (est.) Oct 17 – Nov 20 |
| Spinach · Fall sow4–7 weeks before first fall frost (Virginia Tech) | Aug 2 – Aug 23Harvest (est.) Sep 16 – Oct 22 | Aug 10 – Aug 31Harvest (est.) Sep 24 – Oct 30 | Aug 25 – Sep 15Harvest (est.) Oct 9 – Nov 14 |
| Radishes · Fall sow4–6 weeks before first fall frost | Aug 9 – Aug 23Harvest (est.) Aug 29 – Sep 22 | Aug 17 – Aug 31Harvest (est.) Sep 6 – Sep 30 | Sep 1 – Sep 15Harvest (est.) Sep 21 – Oct 15 |
| Daffodils · Fall plant bulbs4 weeks before to 2 weeks after first fall frost (our approximation of when soil falls below 60°F; Rutgers) | Aug 23 – Oct 4 | Aug 31 – Oct 12 | Sep 15 – Oct 27 |
| Tulips · Fall plant bulbs2 weeks before to 4 weeks after first fall frost (our approximation of when soil falls below 60°F; Rutgers) | Sep 6 – Oct 18 | Sep 14 – Oct 26 | Sep 29 – Nov 10 |
| Garlic · Fall plant cloves2 weeks before to 3 weeks after first fall frost, while the soil is still workable (SDSU, Illinois, Virginia Tech) | Sep 6 – Oct 11Harvest (est.) May 14, 2027 – Jul 8, 2027 | Sep 14 – Oct 19Harvest (est.) May 22, 2027 – Jul 16, 2027 | Sep 29 – Nov 3Harvest (est.) Jun 6, 2027 – Jul 31, 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
Idaho 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 Idaho 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 Idaho?
Across the 280 Idaho ZIP codes where frost comes in most years, the median last spring frost (32°F, NOAA 1991–2020) at the nearest station is May 15, and the middle 80% of ZIP codes range from Apr 24 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 Idaho?
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 30 – Jun 6; Zone 6 areas: May 22 – May 29; Zone 7 areas: May 6 – May 13.
What USDA zone is Idaho?
Idaho spans roughly USDA hardiness zones 4a–7b 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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