Plant Kale in Zone 5a

Zone 5a averages 156 frost-free days, running from a last spring frost around April 30 to a first fall frost around October 3. Kale needs roughly 60 days from planting out to first harvest, so it uses about 38 percent of that window. Kale is a hardy crop, which is what decides where in the window it belongs.

Because kale needs a head start, sow seed indoors around Mar 19, about 6 weeks ahead of the Zone 5a last frost. Transplants go out around Apr 16. Starting earlier than that in Zone 5a usually backfires: plants outgrow their cells and stall when they finally hit cold soil. At 60 days to harvest, a 156-day Zone 5a season has room for about 2 sowings, so stagger them rather than planting everything at once.

Yes. Sow kale by August 18 in Zone 5a. That is 46 days before the average first frost, which covers the 60 days to maturity plus about two weeks for the slower growth that comes with shortening days, minus the roughly 28 days kale keeps going once light frost arrives.

Kale is usually the last thing standing in the garden. Frost converts its starch to sugar, so the flavour improves after the first freeze.