Plant Broccoli in Zone 3a

Zone 3a averages 123 frost-free days, running from a last spring frost around May 15 to a first fall frost around September 15. Broccoli needs roughly 65 days from planting out to first harvest, so it uses about 53 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 Apr 3, about 6 weeks ahead of the Zone 3a last frost. Transplants go out around May 1. Starting earlier than that in Zone 3a usually backfires: plants outgrow their cells and stall when they finally hit cold soil.

Yes. Sow broccoli by July 19 in Zone 3a. 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.