Growing Guide: September in the Bay Area (USDA Zones 9–10)

Growing Guide: September in the Bay Area (USDA Zones 9–10)

September is the Bay Area hand-off from summer to cool-season veggies. Clear tired beds, refresh soil, and pivot to fast, flavorful greens and roots. You’ll get steady harvests into winter if you start now. Alameda and San Mateo/SF Master Gardeners emphasize planting cool-season crops through September while tidying and mulching beds.

This Free guide keeps it USDA-simple: what to sow, what to transplant, and the few tasks that move the needle most. For microclimate-exact timing, weekly checklists, and pest defense, the Premium Masterclass goes deeper.

What to Plant / Key Actions

• Direct-sow now: lettuce, spinach, arugula, kale, chard, radish, turnip, carrot, beet, cilantro; in many areas, peas late month. Local gardening calendars list these as prime fall crops.

• Transplant now: broccoli, cauliflower, cabbage. Santa Clara MGs back-calculate mid-September broccoli transplants to ~6 weeks of seedling time.

• Prep & refresh: pull non-productive summer crops; add 1–2” compost; restore 2–3” mulch to even moisture and reduce weeds.

Step-By-Step Basics

1. Prep beds — Remove spent plants; compost only disease-free material. Top-dress with compost; check irrigation before you sow.

2. Sow/Transplant — Sow shallow, keep seedbeds evenly moist; set brassicas at the same depth they grew in pots; firm soil to remove air pockets.

3. Watering — Aim for steady moisture to prevent bitter greens and split roots; mulch helps stabilize swings.

4. Pest watch (light) — White butterflies now = cabbageworm later; floating row cover prevents egg-laying. Hand-pick or use Bt/spinosad if needed.

5. Harvest cues — Radishes ~25–35 days; baby greens in 3–4 weeks; carrots/beets when roots size up and tops color well.

GrowBot did some digging… Sow little, weekly. A handful of lettuce/radish rows each weekend beats one big sowing — fresher salads, fewer gaps.

Peas need cool soil. If your bed stays warm, hold peas until late September and mulch after germination.

Shield brassicas early. A $10 row cover now saves you hours of caterpillar patrol later.

Next Steps

Want microclimate-specific timing (Sunset + USDA), a week-by-week September checklist, a pest watchlist, and heirloom picks that excel here? The September Premium Masterclass has it all.