Idaho Gardening Guide (2026)

High desert and mountain valleys; cold nights, hot days, short season.

USDA hardiness zone
3โ€“7
Region
Mountain
Typical last spring frost
05/10
Typical first fall frost
10/01
Frost-free season
144 days
Lawn grass type
Cool-season

Quick answer (Idaho): Most of the state gardens in USDA zones 3โ€“7 with about a 144-day frost-free window. Plan around the typical last frost of 05/10; start warm-season crops indoors ~6 weeks earlier. Source: USDA Plant Hardiness Zone Map (2023) + state cooperative extension typical freeze dates.

Your Idaho planting calendar

Pre-filled for Idaho. Pick a crop to see indoor start, sow/transplant, and harvest dates you can print.

In Idaho (typical zone 3โ€“7, last frost โ‰ˆ May 10, first frost โ‰ˆ Oct 1, 144-day season), your Tomato plan:

Start seeds indoors
Mar 29
Sow / transplant outdoors
May 24
First harvest
Aug 2
Spacing / depth
24โ€ณ / 0.25โ€ณ

Month-by-month (Idaho, 2026)

MonthAction
Janโ€”
Febโ€”
MarStart indoors
Aprโ€”
MaySow ยท Transplant
Junโ€”
Julโ€”
AugHarvest
Sepโ€”
Octโ€”
Novโ€”
Decโ€”

Start indoors 6 weeks before last frost; transplant after soil warms. Zones 3โ€“13 suitable. Dates are typical; confirm with your county extension and watch the 10-day forecast.

Lawns in Idaho

Best grass types for your climate:

Kentucky BluegrassTall FescuePerennial RyegrassFine Fescue

Open the lawn care scheduler โ†’

Common pests in Idaho

The pests most reported in your region, with organic-first treatments:

CutwormAphidsGrasshopper

Cutworm

Targets
Seedlings of many crops
Signs
Young transplants cut at soil line overnight.
Organic / IPM first
Cardboard collar around stem; diatomaceous earth ring; hand-pick at dusk.
Chemical option (follow label)
Bt or spinosad soil drench at planting.
Prevention
Till in fall; avoid fresh manure; start transplants sturdy.

What grows well in Idaho

Crops suitable for zones 3โ€“7:

CropTypeSpacingDays to harvest
TomatoWarm-season24โ€ณ70
PepperWarm-season18โ€ณ75
LettuceCool-season8โ€ณ45
CarrotCool-season3โ€ณ65
Green BeansWarm-season4โ€ณ55
SpinachCool-season6โ€ณ40
CucumberWarm-season12โ€ณ55
ZucchiniWarm-season36โ€ณ50
KaleCool-season12โ€ณ55
BroccoliCool-season18โ€ณ70

Figures are typical (30-year normals) from USDA and state extension services. Always confirm your local last/first freeze and product labels with your county extension before acting.