Growing Guide: Swiss Chard — Bay Area (USDA Zones 9–10)

Swiss chard is a cool‑season, cut‑and‑come‑again staple that tolerates light heat and mild frost. Aim for quick, steady growth: fertile soil, even moisture, and regular harvests. Chard is a biennial typically grown as an annual here.

When to plant (USDA 9–10)

• Prime windows: early spring and early fall; shoulder months are workable with light protection.

Site & soil

• Full sun near the coast; light afternoon shade inland during warm spells.

• Loamy, well‑drained soil rich in compost; pH roughly 6.0–6.8 for best uptake.

Sowing & spacing

• Direct sow ½” deep; thin to 12–18” between plants (rows ~18–24”).

• For baby chard, sow thick, then harvest at 3–5” tall.

Water & feeding

• Keep soil consistently moist; mulch 2–3” to buffer heat and conserve water.

• If growth slows, side‑dress with compost or a light, balanced feed.

Harvest

• Baby leaves: ~25–35 days; full leaves: ~45–60+ days.

• Harvest outer leaves; keep the crown active for months of regrowth.

Pest & disease watch

• Leafminers: serpentine mines; remove mined leaves, protect seedlings with row cover; treatment rarely needed in home gardens.

• Powdery mildew (late season): choose good airflow, water mornings, avoid excess N; fungicides typically unnecessary for home gardens.

Sources:

• UC ANR Marin — Chard (soil pH and growth notes) (https://ucanr.edu/site/uc-marin-master-gardeners/documents/chard-swiss-chard).

• UC IPM — Vegetable leafminers (https://ipm.ucanr.edu/PMG/GARDEN/VEGES/PESTS/vegleafminers.html)

“GrowBot did some digging: thin early and water evenly—fast growth means sweeter, less miner‑scarred leaves.”