Plant Cilantro in Zone 4b

Zone 4b averages 146 frost-free days, running from a last spring frost around May 5 to a first fall frost around September 28. Cilantro needs roughly 45 days from planting out to first harvest, so it uses about 31 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 Apr 21, roughly 2 weeks before the Zone 4b 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 146-day Zone 4b season has room for about 2 sowings, so stagger them rather than planting everything at once.

Yes. Sow cilantro by August 14 in Zone 4b. 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.