When to plant zucchini / summer squash in North Dakota
North Dakota’s average last spring frost is May 15, and the first fall frost typically arrives around September 20 — about 128 frost-free days (USDA zones 3a, 3b, 4a, 4b). Zucchini / Summer Squash needs 45–60 days to mature, which fits comfortably within North Dakota's growing season.
When to plant zucchini / summer squash in North Dakota: the short answer
For a spring planting, plant out May 15 – Jun 1, with seeds started indoors Apr 17 – May 1. Wait until the soil is at least 60°F and frost is over.
Succession sow again in North Dakota: Jun 19 · Jul 17
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 zucchini / summer squash in North Dakota, step by step
- Start seeds indoors (Apr 17 – May 1). Sow seeds 1 inch deep in seed-starting mix under bright light. They take 5-10 days to sprout, fastest in soil around 85°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 14 inches deep, with a pH between 5.5 and 7.5. Dig in compost before planting.
- Plant out (May 15 – Jun 1). Space plants about 30 inches apart in rows 42 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: squash vine borer, squash bug, striped cucumber beetle, aphids. Diseases and disorders: powdery mildew, bacterial wilt, blossom-end rot (calcium disorder).
- Harvest (from about Jul 6 – Jul 21). Zucchini / Summer Squash takes 45-60 days to reach harvest. One or two plants feed a household. A second sowing in early-mid summer dodges the first vine borer generation.
Figures come from our crop data; dates use North Dakota’s average frost dates. More in the full zucchini / summer squash growing guide.
Zucchini planting dates by USDA zone in North Dakota
North Dakota spans USDA zones 3a, 3b, 4a, 4b. 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 zucchini / summer squash dates shift with them.
When to plant zucchini / summer squash in nearby states
| State | Last frost | Plant out |
|---|---|---|
| North Dakota (this page) | May 15 | May 15 – Jun 1 |
| South Dakota | May 10 | May 10 – May 27 |
| Nebraska | April 30 | Apr 30 – May 17 |
| Kansas | April 15 | Apr 15 – May 2 |
| Oklahoma | April 1 | Apr 1 – Apr 18 |
Questions gardeners in North Dakota ask
When is the best time to plant zucchini / summer squash in North Dakota?
Plant zucchini / summer squash transplants outdoors in North Dakota between May 15 and June 1. That timing is set by North Dakota's average last spring frost of May 15.
When should I start zucchini / summer squash seeds indoors in North Dakota?
Start seeds indoors between April 17 and May 1, about 3 weeks before the last frost, so the seedlings are ready to plant out from May 15.
Can I plant zucchini / summer squash in the fall in North Dakota?
Yes. For a fall crop, sow between June 18 and July 5, so the crop matures in cool weather before North Dakota's first frost around September 20.
When will zucchini / summer squash planted in North Dakota be ready to harvest?
Planted on time, zucchini / summer squash is usually ready from about July 6 to July 21, 45-60 days after planting.
When is the last frost in North Dakota?
On average around May 15, with the first fall frost around September 20 - about 128 frost-free days. Your town may differ by two weeks or more.