When to plant broccoli in Montana
Montana’s average last spring frost is May 15, and the first fall frost typically arrives around September 15 — about 123 frost-free days (USDA zones 3a, 3b, 4a, 4b, 5a, 5b, 6a). Broccoli needs 60–85 days to mature, which fits comfortably within Montana's growing season.
Montana 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 broccoli in Montana: the short answer
For a spring planting, plant out Apr 24 – May 11, with seeds started indoors Mar 27 – Apr 10. Seeds germinate in soil from 45 to 85°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 broccoli in Montana, step by step
- Start seeds indoors (Mar 27 – Apr 10). Sow seeds ½ inch deep in seed-starting mix under bright light. They take 5-10 days to sprout, fastest in soil around 75°F. Harden seedlings off for a week before they go outside.
- Prepare the bed. It needs at least six to eight hours of direct sun a day and loose soil at least 18 inches deep, with a pH between 6.0 and 7.0. Dig in compost before planting.
- Plant out (Apr 24 – May 11). Space plants about 18 inches apart in rows 30 inches apart. It tolerates a light frost but not a hard freeze. As a cool-season crop it does best before summer heat arrives in Montana.
- 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: cabbage worm, cabbage looper, aphids, flea beetle, cabbage root maggot. Diseases and disorders: clubroot, black rot, downy mildew.
- Harvest (from about Jun 30 – Jul 25). Broccoli takes 60-85 days to reach harvest. Days to maturity counted from transplant. Keep cutting side shoots after the main head for weeks. Spring crop must size up before heat or it buttons.
Figures come from our crop data; dates use Montana’s average frost dates. More in the full broccoli growing guide.
Broccoli planting dates by USDA zone in Montana
Montana spans USDA zones 3a, 3b, 4a, 4b, 5a, 5b, 6a. 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 broccoli dates shift with them.
When to plant broccoli in nearby states
Questions gardeners in Montana ask
When is the best time to plant broccoli in Montana?
Plant broccoli transplants outdoors in Montana between April 24 and May 11. That timing is set by Montana's average last spring frost of May 15; Montana spans several climates, so cooler and higher parts of the state run later.
When should I start broccoli seeds indoors in Montana?
Start seeds indoors between March 27 and April 10, about 6 weeks before the last frost, so the seedlings are ready to plant out from April 24.
Can I plant broccoli in the fall in Montana?
Yes. For a fall crop, start transplants between June 6 and June 23, so the crop matures in cool weather before Montana's first frost around September 15.
When will broccoli planted in Montana be ready to harvest?
Planted on time, broccoli is usually ready from about June 30 to July 25, 60-85 days after transplanting.
When is the last frost in Montana?
On average around May 15, with the first fall frost around September 15 - about 123 frost-free days. Your town may differ by two weeks or more.