When to plant eggplants 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). Eggplant needs 65–85 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 eggplants in Montana: the short answer
For a spring planting, plant out May 29 – Jun 15, with seeds started indoors Mar 6 – Mar 20. Wait until the soil is at least 70°F and frost is over.
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 eggplants in Montana, step by step
- Start seeds indoors (Mar 6 – Mar 20). Sow seeds ¼ inch deep in seed-starting mix under bright light. They take 7-14 days to sprout, fastest in soil around 85°F. Harden seedlings off for a week before they go outside.
- Prepare the bed. They need at least six to eight hours of direct sun a day and loose soil at least 18 inches deep, with a pH between 5.5 and 6.5. Dig in compost before planting.
- Plant out (May 29 – Jun 15). Space plants about 20 inches apart in rows 30 inches apart. It is killed by frost, so nothing goes outside until the danger has passed.
- 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: flea beetle, Colorado potato beetle, aphids, spider mite. Diseases and disorders: verticillium wilt, phomopsis blight, bacterial wilt.
- Harvest (from about Aug 9 – Aug 29). Eggplant takes 65-85 days to reach harvest. The most heat-demanding common vegetable - do not rush it into cold soil. Flea beetles hammer young plants; a row cover until flowering pays off.
Figures come from our crop data; dates use Montana’s average frost dates. More in the full eggplant growing guide.
Eggplant 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 eggplant dates shift with them.
When to plant eggplants in nearby states
Questions gardeners in Montana ask
When is the best time to plant eggplants in Montana?
Plant eggplant transplants outdoors in Montana between May 29 and June 15. 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 eggplant seeds indoors in Montana?
Start seeds indoors between March 6 and March 20, about 9 weeks before the last frost, so the seedlings are ready to plant out from May 29.
What is the latest I can plant eggplants in Montana?
About July 12. Eggplants need at least 65 days to mature after transplanting, and frost around September 15 ends the season, so later plantings risk being cut short.
When will eggplants planted in Montana be ready to harvest?
Planted on time, eggplants are usually ready from about August 9 to August 29, 65-85 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.