When to plant zucchini / summer squash in California
California’s average last spring frost is February 20, and the first fall frost typically arrives around December 1 — about 284 frost-free days (USDA zones 5a, 6b, 7b, 8b, 9b, 10a, 10b). Zucchini / Summer Squash needs 45–60 days to mature, which fits comfortably within California's growing season.
California 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 zucchini / summer squash in California: the short answer
For a spring planting, plant out Feb 20 – Mar 9, with seeds started indoors Jan 23 – Feb 6. Wait until the soil is at least 60°F and frost is over.
Succession sow again in California: Mar 27 · Apr 24 · May 22 · Jun 19 · Jul 17 · Aug 14 · Sep 11
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 California, step by step
- Start seeds indoors (Jan 23 – Feb 6). 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 (Feb 20 – Mar 9). 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 Apr 13 – Apr 28). 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 California’s average frost dates. More in the full zucchini / summer squash growing guide.
Zucchini planting dates by USDA zone in California
California spans USDA zones 5a, 6b, 7b, 8b, 9b, 10a, 10b. 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.
| Zone | Last frost | First frost | Season | Start indoors | Plant zucchini / summer squash |
|---|---|---|---|---|---|
| Zone 5 | Apr 30 | Oct 5 | 160 days | Apr 2 – Apr 16 | Apr 30 – May 17 |
| Zone 6 | Apr 15 | Oct 15 | 185 days | Mar 18 – Apr 1 | Apr 15 – May 2 |
| Zone 7 | Apr 5 | Oct 25 | 200 days | Mar 8 – Mar 22 | Apr 5 – Apr 22 |
| Zone 8 | Mar 20 | Nov 5 | 230 days | Feb 20 – Mar 6 | Mar 20 – Apr 6 |
| Zone 9 | Feb 20 | Nov 30 | 280 days | Jan 23 – Feb 6 | Feb 20 – Mar 9 |
| Zone 10 | Jan 30 | Dec 15 | 330 days | Jan 2 – Jan 16 | Jan 30 – Feb 16 |
Questions gardeners in California ask
When is the best time to plant zucchini / summer squash in California?
Plant zucchini / summer squash transplants outdoors in California between February 20 and March 9. That timing is set by California's average last spring frost of February 20; California spans several climates, so cooler and higher parts of the state run later.
When should I start zucchini / summer squash seeds indoors in California?
Start seeds indoors between January 23 and February 6, about 3 weeks before the last frost, so the seedlings are ready to plant out from February 20.
Can I plant zucchini / summer squash in the fall in California?
Yes. For a fall crop, sow between August 29 and September 15, so the crop matures in cool weather before California's first frost around December 1.
When will zucchini / summer squash planted in California be ready to harvest?
Planted on time, zucchini / summer squash is usually ready from about April 13 to April 28, 45-60 days after planting.
When is the last frost in California?
On average around February 20, with the first fall frost around December 1 - about 284 frost-free days. Your town may differ by two weeks or more.