When to plant garlic in Idaho
Idaho’s average last spring frost is May 10, and the first fall frost typically arrives around September 25 — about 138 frost-free days (USDA zones 3b, 4b, 5b, 6a, 6b, 7a). Garlic needs 240–270 days to mature, which is tight for a full-season planting there — see the note below.
Idaho covers a wide range of climates, so your exact frost dates may differ from the state average by two weeks or more. For dates tuned to your town, use the calendar generator.
When to plant garlic in Idaho: the short answer
For a spring planting, sow Oct 6 – Oct 23. Seeds germinate in soil from 32 to 75°F.
Windows are ~1–2 week bands around each date. Frost dates are a statewide average from NOAA/NCEI normals; your town may differ by two weeks or more. Calendar year 2026.
How to grow garlic in Idaho, step by step
- Prepare the bed. It needs at least six to eight hours of direct sun a day and loose soil at least 12 inches deep, with a pH between 5.5 and 7.5. Dig in compost before planting.
- Water and feed. Give it steady, even moisture, about an inch of water a week from rain or the hose.
- Watch for pests and problems. Pests: onion maggot, onion thrips, stem nematode. Diseases and disorders: white rot, rust, basal rot.
- Harvest. Garlic takes 240-270 days to reach harvest. Plant cloves 2-4 weeks after the first fall frost, pointy end up, and mulch. Hardneck types need this cold period; softneck types suit mild-winter regions and braid well. Harvest the following summer when the lower leaves brown.
Figures come from our crop data; dates use Idaho’s average frost dates. More in the full garlic growing guide.
Garlic planting dates by USDA zone in Idaho
Idaho spans USDA zones 3b, 4b, 5b, 6a, 6b, 7a. Colder zones, usually higher or further inland, have a later last spring frost and an earlier first fall frost than the state average, so the garlic dates shift with them.
When to plant garlic in nearby states
Questions gardeners in Idaho ask
When is the best time to plant garlic in Idaho?
Plant garlic in Idaho between October 6 and October 23. That timing is set for fall, after Idaho's first frost (about September 25); Idaho spans several climates, so cooler and higher parts of the state run later.
When will fall-planted garlic be ready in Idaho?
The following June to July. Garlic roots in fall, rests over winter and finishes in early summer - harvest when the lower leaves turn brown.
When is the last frost in Idaho?
On average around May 10, with the first fall frost around September 25 - about 138 frost-free days. Your town may differ by two weeks or more.