how to grow kale, with sarah kleeger of adaptive seeds

dark purple kale‘ANYONE CAN GROW KALE,’ the seed farmers at Adaptive Seeds—who have collected kales from around the world and made them a specialty—said to me, 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.”

Here’s what else I learned in Sarah’s and my Q&A (that’s her with Andrew and some of their other specialty crops, winter squash, below):

ndrew Still and Sarah Kleeger of Adaptive Seeds

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.

Kale diversity photo, Nick RoutledgeQ. Of the kales you offer at Adaptive, can you give me a tour of which one is “best” for what? [Photo above, by Nick Routledge, shows some of the great diversity of kale.]

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.

tomato-cages-upmore from adaptive seeds, and about kale

(Photos from Adaptive Seeds, except kales on shed wall from Nick Routledge; top one of purple kale, Margaret Roach.)

  1. Margaret, I’m in zone 5B too. Is it the baking sun that toughens the kale, or the ambient air temperature? I’m wondering, if i planted the kale in big box on a dolly, I could roll it into a shady spot when it gets too hot…would this help? Am I cracked to think I could lug the thing? Can you tell I love kale?

  2. lou desena says:

    I’m confused( doesn’t take too much to “confuse me)–I want to grow Tuscan kale here in ct.

    I want to grow it in the garden from “seed”.–“when” should I plant it for “best picking??”.


  3. Joan Lindquist says:

    I have grown kale and loved it. However, I’ve had a problem controlling white fly. Any suggestions? I was told that if white fly is a problem, plants should not be overwintered.

    1. Alan Gorkin says:

      we have the same problem. it doesn’t seem to die in the cold either, so we feed whats left to the hens and pull the rest out. the stuff we eat we just presoak in warm water and they float to the top. then take a season off from fall kale to break the cycle.

  4. Mathew G says:

    I bought far more kale seeds than I’ll ever need after seeing Adaptive seeds featured on this site a few months back. They have some of the fanciest and interesting varieties I’ve ever seen. My plan is to do all my kale as a fall crop; in previous years when I’ve grown it as spring crop, the grey aphids get so bad that there’s no way I can even stomach the possibility of eating the kale, so it gets wasted. I’m hoping that a late summer planting will provide lots of aphid-free kale in October and November.

  5. Cindy says:

    After giving up on summer-harvested kale in western Mass, one spring I grew it under row cover on someone’s advice and avoided bugs until August, freezing the harvest, until finally the cover was breached enough that the bugs got in. While we had a great harvest that year, I went back to strictly fall kale because in succeeding years bugs got it (emerged from the soil, I think?) regardless of the row cover.

    But I have a place for buggy kale: the chickens can eat it.

    1. margaret says:

      Hi, Cindy. Yes, they are devils, right? Up from the soil. I try to move the brassicas around as best as I can, skipping two years in between planting in the same spot (so a 3-year rotation).

  6. Eleanor says:

    I’m trying “flower sprouts” this year. Have you tried them Margaret? It seems they were developed in Lincolnshire UK and I bought and ate some when I was there visiting family a month ago. They’re amazing! Here’s the description:
    Flower Sprouts® is a novel class of vegetables bred by crossing Brussels sprouts and kale. They resemble colorful flowers or rosettes that grow on stalks of tall, upright plants just like Brussels sprouts.
    The tender, mildly flavored spouts have a taste and texture similar to Red Russian kale. Flower Sprouts® are suited to diverse cooking methods such as lightly steaming, sautéing, stir frying, and roasting. When lightly cooked they will hold their color.

  7. shiner says:

    I start my kale in Winter Sown jugs and they actually started to come up a month ago! The sweeds are out from Jan on the deck and have snow and ice on top at times, live through temps of 0 degrees and come up each year. I wait til they are about 2 inches tall before transplanting them. That ususally is about mid April. I live in 6B in the mountains of NC.
    (I also start some squash and tomatos this way)

  8. Colleen says:

    WOW…I didn’t know you could/should start kale inside. I will try this soon as living in zone 4b…my “outside” time is later …and this year who knows. The garden is still covered by a foot or more of snow.

  9. Will Scruggs says:

    I live at lower elevations in Hawaii. I have had some success with Kale in the winter. Do you have suggestions for warm weather types?

  10. Jae says:

    OK, I live in zone 10b. I know I am out of luck for summer growing but can I grow good tasting kale in the winter? I love kale so much!

    1. margaret says:

      Hi, Jae. It’s a winter crop for you, yes. I have just been reading articles on growing kale from Sonoma County Master Gardeners and even Master Gardeners of San Diego etc. Fall planting (September or October — not sure where you live) for winter into early spring harvest. You can get a longer harvest if you sow some seeds indoors a few weeks ahead to transplant, and also self-sow in fall at the same time you transplant the indoor ones.

  11. Bronte says:

    Great article! This may have just inspired me to grow my own kale! Except in Perth, Australia we rarely get frost… Would it still taste like it’s been dipped in honey? Because that sounds amazing! I’ve never had the raab before but they sound delicious – a cross between a couple of my favourite vegetables! I would love to be able to cook a whole meal with everything home grown but I think I will first have to work on my patience…

    1. LP says:

      I know this is a bit late but anyone can grow kale or any other leafy vegetable in an aquaponics system, not to mention growing year round without care of the weather and providing fresh edible fish too (we use tilapia in ours)..

  12. Kelsey says:

    Great post, kale is becoming a very popular ‘super food’ and knowing how to grow it yourself would be great. Love the question and answer format.

  13. Chris Baswell says:

    I love kale and try to grow it often, but it attracts cabbages worms more than anything else in my garden. I’ve tried floating row cover, but the little white butterflies seem to find their ways inside, and I’ve produced a nice protected environment for the larvae. Any thoughts? Thanks! Chris

  14. Don Shull says:

    As a southerner in the 50s, I had parents who something in the kohl family at least five nights a week, regardless of what other vegetables were on the table. We had to take a serving spoon of everything. My parents would say, “You might like this. It’s not turnip greens; it’ mustard” or “it’s not mustard; it’s kale.” My sister and I hated it all. Broccoli and Brussels sprouts were a respite. My older sister gave me the following epistemology problem, “Mother and Daddy say they love greens. We’ve tasted greens and know this is impossible: they’re horrible. Yet Mpther and Daddy NEVER deceive us for our own good. How to judge?” Luckily, after about ten years of this, I learned to enjoy and even crave greens.

  15. Judy says:

    I always had trouble transplanting July-started kale seedlings, because here it’s hot and dry in July/August, bad timing for transplanting. Then I started planting a pinch of seed every foot and thinning to the strongest one. The thinnings go in salad and no transplanting is needed. This has also worked for fall broccoli.

  16. Julie Martin says:

    Confused, does she start her summer planting in the greenhouse also? I want to try summer planting. Thanks!

  17. Katherine Tremblay says:

    Growing kale under a hoop row covered with fine nylon tulle solved our cabbage moth problem. The fabric is cheap and easy to work with, lets in plenty of light and water. It’s available in 108″ width and the black is almost invisible.

  18. Linda Bridges says:

    Loved the article on Kale! I tell people that I can’t not grow Kale…. It grows here in Scarborough Maine like I’ve never seen. Furthermore, perhaps a benefit of global warming, my Kale( and tomatoes) have begun reseeding themselves and I frequently have a two year old row or cluster of Kale! It never would have happened 10 years ago…. I do very little to help it. A little compost, bit of manure!

  19. Ray Hassard says:

    I’ve been growing kale from my own seeds for years but the last 2 years have been terrible for blue-grey aphids. This past summer they got nearly all the kale, broccoli and hide inside the brussel sprouts. I noticed they have made it through the winter and pulled up the remains of all those crops. I spent far too long cleaning off the bugs and trying to salvage what I could from my crops (NOT going to let those bugs get it all!). I tried all the conventional means to rid plants of aphids and nothing worked. Does anyone have any ideas? I’m reluctant to plant any brassicas this summer at this point.

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