Plant Broccoli in Zone 9b

Zone 9b averages 298 frost-free days, running from a last spring frost around February 15 to a first fall frost around December 10. Broccoli needs roughly 65 days from planting out to first harvest, so it uses about 22 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 Jan 4, about 6 weeks ahead of the Zone 9b last frost. Transplants go out around Feb 1. Starting earlier than that in Zone 9b usually backfires: plants outgrow their cells and stall when they finally hit cold soil. At 65 days to harvest, a 298-day Zone 9b season has room for about 3 sowings, so stagger them rather than planting everything at once.

Yes. Sow broccoli by October 13 in Zone 9b. 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.