Plant Cilantro in Zone 10b

Zone 10b averages 350 frost-free days, running from a last spring frost around January 15 to a first fall frost around December 31. Cilantro needs roughly 45 days from planting out to first harvest, so it uses about 13 percent of that window. Cilantro is a half-hardy crop, which is what decides where in the window it belongs.

Cilantro handles cold soil, so there is no reason to wait for the frost date. Direct sow around Jan 1, roughly 2 weeks before the Zone 10b last frost, as soon as the ground is workable. Sowing at the last frost instead costs you the coolest and best part of the season. At 45 days to harvest, a 350-day Zone 10b season has room for about 5 sowings, so stagger them rather than planting everything at once.

Yes. Sow cilantro by November 16 in Zone 10b. That is 45 days before the average first frost, which covers the 45 days to maturity plus about two weeks for the slower growth that comes with shortening days, minus the roughly 14 days cilantro keeps going once light frost arrives.

Cilantro bolts within weeks in summer heat and is far more productive as a fall crop, and in mild zones it runs right through winter.