When to Plant Zucchini in California
Published: April 21, 2026
California gardeners in Zone 9b enjoy an extended 50-week growing season for zucchini. Warm-climate gardeners can grow two zucchini crops — a spring planting and a fall planting — with summer heat as the main challenge to work around. This guide gives exact dates for California based on your local frost calendar.
Zucchini Planting Dates for California
| Start seeds indoors | December 25–January 1 |
| Last frost (average) | January 15 |
| Transplant outdoors | January 22–February 1 |
| Direct sow outdoors | January 22–February 1 |
| Expect first harvest | March 8 – March 18 |
| Fall crop start | November 5–15 |
| Fall harvest | December 20 |
| First fall frost (average) | December 31 |
Dates above assume Zone 9b, the most common zone in California. Gardeners in cooler Santa Rosa (Zone 6b) plant 1–2 weeks later; warmer San Francisco (Zone 10b) can plant 1–2 weeks earlier.
Growing Zucchini in California's Climate
California's warm Zone 9b climate gives zucchini more than enough heat — in fact, peak summer heat (95°F+) can shut down fruit set entirely. The solution most California gardeners use is a two-season approach: a spring crop planted early, a harvest break during peak summer, and a fall crop planted July through August for October and November harvest.
Variety selection matters more in warm climates than most gardeners realize. Choose heat-tolerant varieties bred for California-like conditions — local extension offices and nurseries stock these specifically. Afternoon shade cloth during July and August can be the difference between a working fall crop and total flower drop.
Common zucchini pests to watch for in California include Squash Vine Borer and Squash Bug. The first line of defense is companion planting: Corn and Bush Beans planted nearby discourage several of these pests by confusing host-plant identification or repelling adults before they can lay eggs. Weekly garden walks in the early morning catch problems when they're still manageable.
Zucchini Garden Calendar for California
| Month | Task | Notes |
|---|---|---|
| January | Transplant outdoors | Soil temp must be 65°F+; nighttime lows above 50°F |
| February | — | Off-season |
| March | First harvest window opens | Zucchini begins producing 45–55 days after transplant |
| April | — | Off-season |
| May ← | — | Off-season |
| June | Peak growth; water 1 inch/week | Monitor for pests daily; stake or support as needed |
| July | Start fall crop seeds | Fall transplants go in 8 weeks before first frost |
| August | — | Off-season |
| September | — | Off-season |
| October | — | Off-season |
| November | Fall crop planting | Transplant or direct sow for fall harvest before frost |
| December | Start seeds indoors | Use grow lights; warm soil to 70–75°F for best germination |
Zucchini Growing Tips for California Gardeners
- •Start with just 1–2 plants — zucchini are so productive that more is rarely needed.
- •Harvest at 6–8 inches for peak flavor; zucchini left on the plant signals it to stop producing.
- •California's summer heat shuts down zucchini flowering at 95°F+. Choose heat-tolerant varieties and use shade cloth from mid-June through August to preserve fruit set.
- •California's fall crop is often more productive than spring — plant transplants in July after the worst heat, for October and November harvest as temperatures cool.
- •Plant a backup crop in early July to replace any vine borer losses in the eastern US.
Companion Planting for Zucchini in California
In California's warm climate, planting zucchini with Corn and Bush Beans helps deter pests and improve soil. Avoid planting near Potato and Fennel, which inhibit zucchini growth through root chemistry or shared pest pressure. See the full zucchini companion planting guide for the complete list.
Zucchini Planting Dates by City in California
Top cities in California — select for city-level frost dates and planting calendars.
Frequently Asked Questions
When should I plant zucchini in California?
In California (Zone 9b), start zucchini seeds indoors around December 25–January 1 and transplant outdoors around January 22–February 1 — 1 weeks after the state's average last frost of January 15.
What is the last frost date in California?
California's average last frost date is January 15 in the state's most common Zone 9b. Frost dates vary by city — higher elevations and northern counties run 1 to 3 weeks later than the state average. See the city list below for city-level frost dates.
Can I grow zucchini year-round in California?
Not year-round — California's cold season stops zucchini production. The zucchini season runs January 15 to December 31, roughly 50 weeks. A fall crop extends harvest into late autumn.
What zucchini varieties grow best in California?
For California's Zone 9b, Costata Romanesco and Tromboncino tolerate heat while producing high-quality fruit.
When do I start zucchini seeds indoors in California?
Start zucchini seeds indoors in California around December 25–January 1, which is 3 weeks before the state's average last frost of January 15. Use grow lights and keep soil temperatures at 70–75°F for fastest germination.