When to Plant Vegetables in Idaho

Last updated September 6, 2026

Last spring frost (median)

May 15

First fall frost (median)

Sep 26

Growing season

~134 days

Across Idaho, the median last frost falls around May 15 and the median first fall frost around Sep 26, from NOAA's 1991-2020 climate normals for the weather station nearest each of the state's ZIP codes. Half of years have a later last frost; 1 year in 10 is later than about Jun 3. Every date in the table below is calculated directly from those two dates using standard, extension-verified planting-offset rules, and the ZIP box recalculates it for your own station.

Idaho Planting Calendar

Crop	Method	Spring window	Fall window
Tomatoes (Frost-sensitive)	Start Indoors	Start indoors: Mar 20 - Apr 3 Transplant outdoors: May 22 - May 29 Transplant once nighttime lows are reliably above 50°F, not just after the calendar frost date.	None
Peppers (Frost-sensitive)	Start Indoors	Start indoors: Mar 6 - Mar 20 Transplant outdoors: May 29 and later Peppers want warmer soil than tomatoes -- when in doubt, wait the extra week.	None
Cucumbers (Frost-sensitive)	Direct SowTransplant	May 22 - May 29 The real trigger is soil temperature (70°F+ at 1 inch deep), not the calendar -- this window is a practical estimate of when that soil temperature typically arrives after the last frost.	None
Beans (Frost-sensitive)	Direct Sow	May 15 - May 22 Bean seed rots in cold, wet soil -- wait until the soil has warmed to at least 60°F.	None
Lettuce (Frost-tolerant)	Direct Sow	Apr 17 - May 1 Cold-tolerant -- a good candidate for succession sowing every 2-3 weeks through spring.	Sow by Jul 24 - Aug 3
Carrots (Frost-tolerant)	Direct Sow	Apr 10 - May 1	None
Squash / zucchini (Frost-sensitive)	Direct SowTransplant	May 15 - May 22 Squash doesn’t tolerate cold -- wait for soil to reach about 70°F.	None
Broccoli (Frost-tolerant)	Start Indoors	Mar 20 - Apr 3	Sow by Jun 24 - Jul 4
Spinach (Frost-tolerant)	Direct Sow	Apr 3 - Apr 17 Sow as soon as the soil can be worked -- extension sources cite anywhere from 2-8 weeks before last frost depending on region; this is a middle estimate.	Sow by Jul 14 - Jul 24
Peas (Frost-tolerant)	Direct Sow	Apr 3 - Apr 17 Cold-tolerant -- sow as soon as the soil can be worked.	None
Onions (sets or transplants) (Frost-tolerant)	Transplant	Apr 17 - May 1 This window is for long-day onion varieties, the standard choice across most of the US. Gardeners in the Deep South growing short-day varieties follow a different fall/winter planting schedule.	None
Radishes (Frost-tolerant)	Direct Sow	Apr 3 - Apr 17 Fast-maturing -- a reliable succession crop every 1-2 weeks through spring.	None
Corn (Frost-sensitive)	Direct Sow	May 15 - May 22 Needs soil temperature of at least 50°F to germinate, with 65-75°F optimal for even germination.	None
Pumpkins (Frost-sensitive)	Direct Sow	May 15 - May 22 Soil should reach about 65-70°F. If timing for a fall harvest target, count backward from your target date using the variety’s days-to-maturity instead of using this spring window.	None
Beets (Frost-tolerant)	Direct Sow	Apr 17 - May 1	None
Cabbage (Frost-tolerant)	Start Indoors	Mar 20 - Apr 3	None
Cauliflower (Frost-tolerant)	Start Indoors	Mar 20 - Apr 3 Extension sources vary more on this crop than most (some cite as few as 4 weeks, others up to 10) -- this range is a defensible middle estimate, usually grown on the same schedule as cabbage.	None
Kale (Frost-tolerant)	Direct Sow	Apr 3 - Apr 17	Sow by Jul 24 - Aug 3
Basil (Frost-sensitive)	Start Indoors	Start indoors: Mar 20 - Apr 3 Transplant outdoors: May 29 and later Frost-sensitive, unlike the cold-tolerant crops above -- transplant only after ALL frost risk has passed and soil has warmed to 60°F or more.	None

Summer vegetable beds full of potatoes, beans, squash and tomatoes in a backyard garden in southern Idaho, with sagebrush hills, poplars and wide skies — The same kind of garden in summer: potatoes, beans, squash and tomatoes. AI-generated image.

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The Spacing & Planting Cheat Sheet

When to start, when to plant, how far apart.

Understanding Your Planting Windows

These windows come from a simple, real calculation: take Idaho's median last-frost and first-frost dates, then apply fixed, extension-verified offset rules for each crop (for example, "start tomato seeds indoors 6-8 weeks before your last frost"). Because the offset rules are the same nationwide but Idaho's actual frost dates are specific to Idaho, the resulting dates are genuinely Idaho's own, not a generic template.

These are statewide medians, though, and your own yard may run warmer or colder depending on elevation, urban heat, or microclimate. Enter your ZIP code in the box at the top of the page for your nearest station's dates. For Idaho's full zone range from coldest to warmest areas, see the Idaho Growing Zone page.

Want exact seed-starting dates for your specific ZIP code, not just the state average? Use the Seed Starting Calculator.

Sources & further reading

Frost dates come from NOAA NCEI's U.S. Climate Normals, 1991-2020: for each of Idaho's ZIP codes, the median last and first 32°F dates at the nearest weather station (an airport station within 15 miles where there is one), with ZIP code points from the U.S. Census Bureau's 2023 ZCTA Gazetteer. The same station data drives our Frost Date Calculator. Planting-offset rules are drawn from US Cooperative Extension sources including UGA, UMN, NC State, Utah State, Iowa State, Penn State, and UConn Extension, cited crop-by-crop in the table above. For more on how we build and verify reference data across this site, see our methodology page.

Planting calendars for nearby states

Frost dates shift gradually across state lines, not sharply:

Or browse all 51 state planting calendars.