Since our Bay Area winters are so mild, spinach seeds can be grown anytime, especially as a fall, winter, and early spring crop.
Sow spinach seeds in a single layer and cover with 1/2 inch of Sloat Organic Compost. Thin established seedlings to 3-4 inches apart. Use Harvest Guard to protect from leaf miner, and Sluggo to keep slugs and snails away from plants.
When seedlings emerge, the first pair of leaves to show are the cotyledons which can look very different from the larger spinach leaves that follow, called “true” leaves. Spinach baby greens are ready to harvest 25 to 30 days after sowing, when they have true leaves, at 2″–4″. Harvest mature plants (when they are 6-12” high) by cutting entire clump at ground level. Cool temperatures may slow germination and growth.