When to plant spinach in Colorado
Colorado’s average last spring frost is May 5, and the first fall frost typically arrives around October 1 — about 149 frost-free days (USDA zones 3b, 4b, 5a, 5b, 6a, 7a). Spinach needs 37–45 days to mature, which fits comfortably within Colorado's growing season.
Colorado 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 Colorado: the short answer
For a spring planting, sow Mar 26 – Apr 14. Seeds germinate in soil from 35 to 75°F.
Succession sow again in Colorado: Apr 12 · Apr 24 · May 6 · May 18 · May 30
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 Colorado, 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 26 – Apr 14). 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 Colorado.
- 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 7 – May 15). 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 Colorado’s average frost dates. More in the full spinach growing guide.
Spinach planting dates by USDA zone in Colorado
Colorado spans USDA zones 3b, 4b, 5a, 5b, 6a, 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 Colorado ask
When is the best time to plant spinach in Colorado?
Sow spinach in Colorado between March 26 and April 14. That timing is set by Colorado's average last spring frost of May 5; Colorado spans several climates, so cooler and higher parts of the state run later.
Can I plant spinach in the fall in Colorado?
Yes. For a fall crop, sow between August 3 and August 20, so the crop matures in cool weather before Colorado's first frost around October 1.
When will spinach planted in Colorado be ready to harvest?
Planted on time, spinach is usually ready from about May 7 to May 15, 37-45 days after sowing.
When is the last frost in Colorado?
On average around May 5, with the first fall frost around October 1 - about 149 frost-free days. Your town may differ by two weeks or more.