When to Plant Brussels Sprouts in California
Published: April 24, 2026
California gardeners in Zone 9b enjoy an extended 50-week growing season for brussels sprout. Cool-season crops like brussels sprout do best in fall, winter, and early spring in California — the hot summers bolt these plants before they can be harvested. This guide gives exact dates for California based on your local frost calendar.
Brussels Sprout Planting Dates for California
| Start seeds indoors | December 11–18 |
| Last frost (average) | January 15 |
| Transplant outdoors | April 9–19 |
| Expect first harvest | June 28 – July 18 |
| Fall crop start | October 1–11 |
| 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.
⚠ Brussels sprouts are planted in midsummer for a fall harvest. Count back 90 days from your first fall frost to find the transplant date. Start seeds indoors 4–6 weeks before that date. Flavor improves after frost.
Growing Brussels Sprouts in California's Climate
California's warm Zone 9b climate makes brussels sprout a fall, winter, and early spring crop rather than a summer one. The cool-season window runs roughly October through April in California — plant outside this window and the brussels sprout will bolt (send up a flower stalk and turn bitter) before it produces a harvestable crop.
Succession planting stretches the brussels sprout harvest window. Sow small amounts every two weeks from October through February — you will have staggered harvests rather than a single wave to process all at once. Bolt-resistant varieties extend the usable window an extra three to four weeks into warming weather.
Common brussels sprout pests to watch for in California include Cabbage Worm and Aphid. The first line of defense is companion planting: Onion and Celery 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.
Brussels Sprout Garden Calendar for California
| Month | Task | Notes |
|---|---|---|
| January | Harden off seedlings | Set seedlings outdoors 1–2 hours daily, increasing gradually |
| February | — | Off-season |
| March | — | Off-season |
| April | Transplant outdoors | Soil temp must be 45°F+; nighttime lows above 50°F |
| May ← | Watch for bolting | Harvest promptly; spring heat arrives quickly |
| June | First harvest window opens | Brussels Sprout begins producing 80–100 days after transplant |
| July | — | Off-season |
| August | — | Off-season |
| September | — | Off-season |
| October | Fall crop planting | Transplant or direct sow for fall harvest before frost |
| November | — | Off-season |
| December | Start seeds indoors | Use grow lights; warm soil to 70–75°F for best germination |
Brussels Sprout Growing Tips for California Gardeners
- •Count back 90 days from first fall frost to find the transplant date — this is the most important Brussels sprout timing rule.
- •Pinch the top of each plant about a month before first frost — this channels energy into sprout formation.
- •California's cool-season brussels sprout plants best in October, November, and December for winter and early spring harvest. Spring plantings bolt before producing a harvestable crop.
- •Harvest sprouts from the bottom up as they reach 1-inch diameter; top sprouts finish last.
Companion Planting for Brussels Sprouts in California
In California's warm climate, planting brussels sprout with Onion and Celery helps deter pests and improve soil. Avoid planting near Tomato and Strawberry, which inhibit brussels sprout growth through root chemistry or shared pest pressure. See the full brussels sprout companion planting guide for the complete list.
Brussels Sprouts 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 brussels sprout in California?
In California (Zone 9b), start brussels sprout seeds indoors around December 11–18 and transplant outdoors around April 9–19 — 12 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 brussels sprout year-round in California?
brussels sprout is a cool-season crop in California, with spring and fall windows. Summer heat bolts the plants before they can produce a harvestable crop. Succession planting every 2–3 weeks stretches the harvest window.
What brussels sprout varieties grow best in California?
For California's Zone 9b, consult a local nursery or extension office for brussels-sprouts variety recommendations.
When do I start brussels sprout seeds indoors in California?
Start brussels sprout seeds indoors in California around December 11–18, which is 5 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.