When to plant spinach 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). Spinach needs 37–45 days to mature, which fits comfortably within Idaho's growing season.
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 spinach in Idaho: the short answer
For a spring planting, sow Mar 31 – Apr 19. Seeds germinate in soil from 35 to 75°F.
Succession sow again in Idaho: Apr 17 · Apr 29 · May 11 · May 23 · Jun 4
Spring succession stops before summer heat makes it bolt. Start sowing again in late summer for a fall crop (see the fall window above).
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 spinach in Idaho, step by step
- Prepare the bed. It needs six or more hours of sun for the best growth, though four to six hours in partial shade is enough and loose soil at least 12 inches deep, with a pH between 6.0 and 7.5. Dig in compost before planting.
- Sow outdoors (Mar 31 – Apr 19). Space plants about 4 inches apart in rows 12 inches apart, sowing seed ½ inch deep. It tolerates hard frost, so it is one of the first crops to plant. As a cool-season crop it does best before summer heat arrives in Idaho.
- 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: leaf miner, aphids, flea beetle. Diseases and disorders: downy mildew, white rust, damping off.
- Harvest (from about May 12 – May 20). Spinach takes 37-45 days to reach harvest. Bolts fast in heat and long days - it is really a spring and fall crop. A late-fall sowing under row cover often overwinters for an early-spring cut.
Figures come from our crop data; dates use Idaho’s average frost dates. More in the full spinach growing guide.
Spinach 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 spinach dates shift with them.
When to plant spinach in nearby states
Questions gardeners in Idaho ask
When is the best time to plant spinach in Idaho?
Sow spinach in Idaho between March 31 and April 19. That timing is set by Idaho's average last spring frost of May 10; Idaho spans several climates, so cooler and higher parts of the state run later.
Can I plant spinach in the fall in Idaho?
Yes. For a fall crop, sow between July 28 and August 14, so the crop matures in cool weather before Idaho's first frost around September 25.
When will spinach planted in Idaho be ready to harvest?
Planted on time, spinach is usually ready from about May 12 to May 20, 37-45 days after sowing.
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.