how to grow kale, with sarah kleeger of adaptive seeds
‘ANYONE CAN GROW KALE,’ the seed farmers at Adaptive Seeds—who have collected kales from around the world and made them a specialty—said recently, seeming to beg me to ask, “How?” Do I start indoors, or direct sow? What about spacing, timing, soil prep, aftercare? From the masters, then: How to grow kale.
If you want to coax the best character from your kale-growing efforts, timing is everything, says Sarah Kleeger (half of the Adaptive Seeds team, with Andrew Still).
“First off, unless you live in a place where summers are cool, kale is not a summer vegetable,” she says. “Its flavor and texture improve tremendously in cold, even frosty, weather. In summer it is prone to aphids, the leaves get tough, and taste is markedly less sweet. After a few good frosts kale can taste like it is dipped in honey.”
how to grow kale, the adaptive seeds way
Q. I know you are Oregon, in Zone 7, and you have told me your last frost is maybe mid-May—so people will have to adjust a bit from your timeline, of course. But let’s talk timing first: when, and where, you sow your seeds.
A. We sow kale in two rotations: early spring for a spring/summer rotation, and mid-July for a fall rotation.
Though you can direct sow, we prefer to sow in flats in the greenhouse so plants get a head start on weeds. For us, with our last frost mid-May, planting the spring/summer rotation out the first week of April works well. The soil has warmed and day length is long enough for rapid growth. This means we usually sow at the beginning of March, as plants usually need about 5 weeks from seed to transplant size.
Q. At transplant time, what’s the routine of soil prep and spacing?
A. We plant out with 12-inch spacing in all directions in the garden, and give them plenty of fertility. We use a 4-4-4 organic blend or chicken-manure compost. But if you have a lot of plants and a small amount of space you can squeeze them in and thin as they grow.
Q. Speaking of thinning and such: With all that kale to draw upon in your collection, I suspect you eat a lot of it, yes?
A. Young, tender leaves are great in salads, or wilted greens (I like to put them under the hot food in my bowl to wilt a bit). Larger leaves can also be eaten raw but are best cooked.
Brassica napus kale varieties—the so-called Russo-Siberian kales that mostly have come out of Northern Europe and Northern Asia–tend to be the most tender. ‘Red Russian’ and ‘Siberian’ are the two most well-known napus varieties in the United States.
We prefer Brassica napus kales to Brassica oleracea kales (also called European kale), because the napus are very winter-hardy, with more tender leaves, better flavor, and more general vigor and yield. [An article by Adaptive’s Andrew Still on Russian and Siberian kale.]
Lots of recipes say to throw the kale stems out, but I think they’re a delicious, crunchy snack when raw, and add a nice texture when cooked (just throw them in the pan a few minutes ahead of the leaves). The stems are where the sweetness is.
Q. So at harvest time, do you pull the spring kale? (I know you keep the ones you’re growing for seed going—since you’re seed farmers!—but I mean in the edible garden.)
A. The spring kale rotation can make it through to the next spring if you give it some love mid-summer. Keep it watered, cultivate it, strip off the old leaves, and top-dress it with some fertilizer in the beginning of August.
We don’t tend to eat kale in the summer because there are so many other good things, but we don’t tend to pull it out, either. Larger plants have a lower survival rate through the winter, though, which is one reason we plant again early July for the overwintering crop.
Q. When do we do the next rotation? Here in Zone 5B, in New York State, I usually do it around July sometime.
A. At our 44˚N latitude in Oregon, it is crucial to have the fall rotation of plants in the ground by the second week of August, so the plants can size up before the day length decreases and the growth slows dramatically. Cloud cover also increases dramatically here in the winter—another factor for us.
Usually our kale overwinters just fine, with our lows rarely below 15˚F, but if it gets colder we cover with a frost blanket (row cover). This year we had one week of 5˚F lows, and two of our 12 ‘Kale Coalition’ plants survived uncovered.
Q. I know I’d overwinter my kale if I intended to save seed—so it had time to flower, etc.—but is it edible then?
A. If your kale does make it through the winter, one of the best things about kale is the raab–or flower shoots–that form in the spring. They are almost like a cross between broccoli and asparagus, very sweet and tender when young, and abundant! You can also eat the flowers, and if you don’t, the pollinators will love you for it.
A. True Siberian seems to be the most winter-hardy.
Russian Frills is nice and frilly when large, and makes attractive bunches.
Russian Hunger Gap holds on three weeks later than other kales before bolting (sending up raab), which gives more food later into the “hunger gap,” when your storage veggies are all out and the spring plantings haven’t yet come on.
Madeley is a standout oleracea variety, hugely productive of tender, somewhat smaller leaves, but we’ve sold out and I don’t know anyone else currently offering it.
The Kale Coalition (14 varieties of Brassica oleracea kales that all crossed; photo below and also above) is full of diversity and resilience.
- My recent story on Adaptive’s overall seed-farming operation, including work in winter squash and more
- Browse the Adaptive Seeds catalog online
- Browse all the kales at Adaptive Seeds
- Andrew Weil’s recipe for Tuscan Kale Salad
- My recipe for kale in soupy polenta, a.k.a., Farinata
(Photos from Adaptive Seeds, except kales on shed wall from Nick Routledge; top one of purple kale, Margaret Roach.)