Plant Carrots 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. Carrots needs roughly 70 days from planting out to first harvest, so it uses about 48 percent of that window. Carrots is a hardy crop, which is what decides where in the window it belongs.

Carrots 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.

Yes. Sow carrots by August 3 in Zone 4b. That is 56 days before the average first frost, which covers the 70 days to maturity plus about two weeks for the slower growth that comes with shortening days, minus the roughly 28 days carrots keeps going once light frost arrives.

Carrots convert starch to sugar in cold soil, so fall carrots taste noticeably sweeter. Under a straw mulch they hold in the ground well past the first hard freeze.