Plant Broccoli in Zone 10a

Zone 10a averages 323 frost-free days, running from a last spring frost around January 31 to a first fall frost around December 20. Broccoli needs roughly 65 days from planting out to first harvest, so it uses about 20 percent of that window. Broccoli is a half-hardy crop, which is what decides where in the window it belongs.

Because broccoli needs a head start, sow seed indoors around Dec 20, about 6 weeks ahead of the Zone 10a last frost. Transplants go out around Jan 17. Starting earlier than that in Zone 10a usually backfires: plants outgrow their cells and stall when they finally hit cold soil. At 65 days to harvest, a 323-day Zone 10a season has room for about 4 sowings, so stagger them rather than planting everything at once.

Yes. Sow broccoli by October 23 in Zone 10a. That is 58 days before the average first frost, which covers the 65 days to maturity plus about two weeks for the slower growth that comes with shortening days, minus the roughly 21 days broccoli keeps going once light frost arrives.

Fall broccoli avoids the spring problem of heads buttoning up when temperatures spike. Start transplants indoors in midsummer rather than direct sowing into hot soil.