Plant Kale in Zone 6a

Zone 6a averages 176 frost-free days, running from a last spring frost around April 20 to a first fall frost around October 13. Kale needs roughly 60 days from planting out to first harvest, so it uses about 34 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 9, about 6 weeks ahead of the Zone 6a last frost. Transplants go out around Apr 6. Starting earlier than that in Zone 6a usually backfires: plants outgrow their cells and stall when they finally hit cold soil. At 60 days to harvest, a 176-day Zone 6a season has room for about 2 sowings, so stagger them rather than planting everything at once.

Yes. Sow kale by August 28 in Zone 6a. 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.