Kale and Kin

Young kale plants companion with leeks. Will Bonsall photo

By Will Bonsall

Some years ago I commented to a friend in the seed business about how few kale varieties were available in the marketplace. He hastened to object that there were more kales around than ever, and spouted off a bunch of names, like Red Russian, Hungry Gap, Ragged Jack, Lacinato and so on. I in turn replied that those varieties, while wonderful to grow and eat, are not “true kales” but rather “mustard kales” (Brassica napus). Searching online reveals a lot of confusion and downright errors, much of that propagated by the commercial seed catalogs. Again, I never met a brassica I didn’t like, but they are decidedly different from one another in flavor and uses, so it makes sense to bring some clarity to the matter.

What I call “true kales” are Brassica oleracea var. acephela, all descended from the wild weed “colewort,” a native of the seacoasts of Europe. Examples include Vates, Squire and Konserva. Also derived from colewort (and thus the same species) are cabbage, broccoli, cauliflower, brussels sprouts, collards and kohlrabi. We treat these as distinct foods, but they treat each others as bed partners; that is, they cross readily, in most cases giving us something that is practically useless.

Those are all one species, and related species include turnips, rutabagas (see my article “Rutabagas – They’re Not Really Turnips!” in the summer 2011 MOF&G), mustard greens, Chinese cabbage, Ethiopian cabbage, rape/canola and other lesser-known vegetables.

The taxonomy of Brassicas is confusing and controversial, since some types that are designated as separate species can occasionally cross pollinate, something true species should be unable to do. This is not merely academic, especially if we wish to save our own seed from some of those crops.

A name is whatever we choose to call something, so who’s to say who’s wrong? For example, the locals call one of the wild mustards (the smooth kind, not the prickly kind) that grows as a weed around my place “wild kale,” even though it is nothing of the kind. Again, who are we to gainsay them? Just as rutabagas are often called turnips, and numerous plant species are called “pigweed” or “groundnuts,” etc., common names can confuse, which of course is why Linnaeus came up with the binomial taxonomy system, which, by using “species,” is, well, more specific. So if I say I’m talking about Brassica oleracea (group acephela, or “non-heading”) instead of just calling that vegetable “kale,” maybe we can keep ourselves untangled.

Wikipedia says that kale has been cultivated for many centuries, which is true, but it says the same about collards, which is false. Some sources even claim that kale and collards are the same, which is technically inaccurate. True kale originated directly from colewort. Just as the various B. oleracea types evolved (under human selection) in different regions – cabbage throughout Europe, kohlrabi in Central and Eastern Europe, broccoli in Italy, and brussels sprouts in the Low Countries – collards originated in the American South, as recently as the 18th century, probably as a reverting cabbage. That helps explain the main difference between collards and kales: flat versus crinkly leaves. So when “they” tell us that collards have been used since prehistoric times, they’re misusing their terms.

Likewise when we’re told that kale or collards are used in Ethiopian cuisine, that’s misleading. Ethiopian restaurants in the United States use kale or collards because it’s what they can buy here. In Africa the traditional leafy green is Ethiopian cabbage (B. carinata), a hybrid species that arose along caravan routes where B. oleracea crossed with a wild mustard (much like rutabaga arose from a cross of colewort with “true” turnip, B. rapa). Incidentally, both rutabaga and Ethiopian cabbage exist only under human cultivation and are found nowhere in the wild.

Does clarifying the real meaning behind those names matter? These vegetables are all delicious and nutritious and generally easy to grow, but they do not taste the same. All of the non-colewort descendants have a more pungent taste – “mustardy” or “turnipy” – whereas true kale, like its siblings, has a milder, sweeter taste. A such, true kale is more appropriate for mixing with other vegetables when you don’t want it to overwhelm their flavor; conversely, mixing other veggies (say, carrots) with the mustard kales can tone them down a bit.

Like all the brassicas, kale does best in cool weather. Summer heat and dry soil cause lots of stress-related problems, such as flea beetles and aphids. We’re advised to plant brassicas for early spring and late fall harvest, but for kale in particular, autumn harvest is much preferred. Kale maturing in hot weather tends to be bitter and pungent, whereas fall-grown leaves are milder and sweeter. I have sometimes sown early kale in my eagerness to get some early fresh greens, but generally I prefer rape greens for a quick, early crop and wait for July to seed kale.

For brassicas in general, I often control flea beetles by spraying a homemade extract of rhubarb leaves, or sometimes a fine dusting of sifted wood ash, but with kale I usually have no problem at all. The later I plant (and the sooner I mulch), the more flea beetle populations will have been knocked down by starvation (unless I have a lot of early brassicas nearby). Ample and regular watering is critical in the early weeks, much less so later.

I always plant kale with leeks as a companion, not so much to deter pests as to use space (and water and fertility and every other input) efficiently. The plant forms and root zones are so compatible that they hardly notice each other, allowing me to get more total food per square foot than if I’d planted each crop by itself. Like all my crops, I plant them in intensive beds 4-1/2 feet wide (not counting an 18-inch path). I plant one row of kale down the center and another row 2 feet to either side of that. Alternating with those three rows, I plant two rows of leeks so that each row is 12 inches from its dissimilar neighbor. I set the leek plants out as early as possible – say, early May – whereas I don’t sow kale until July, so the leeks would have all that space to themselves for those months if I let them, but I don’t tolerate such waste. Instead I interplant an early crop such as lettuce, but usually as transplants rather than direct seed, to be sure that crop is all removed in plenty of time for the kale to replace it.

Another trick allows me to leave that intercrop in place even longer. I often start my kale seedlings in a small nursery block (about 4-1/2 feet x 4-1/2 feet) at the end of another bed at the usual time – say, July 10. These rows are 8 inches apart, with seedlings thinned to about 2 to 3 inches within rows. It’s a lot easier to care for that dense cluster of little plants, especially if I need to use a row cover or rhubarb spray. Meanwhile that space in the main bed is still maturing another crop, such as lettuce, since it will be at least a few weeks before I have to transplant the kale.

A common problem with young kale transplants, like most crops, is their tendency to wilt a bit from transplanting shock (unless started in Speedling trays, which in this case takes too much space). My simple remedy is to pinch off the bottom leaf or two while transplanting so that the seedling does not transpire faster than the disturbed roots will allow. The tiny pruned plants look a bit naked, but they rebound much sooner from the disturbance.

Although kale is a robust and resilient plant – which I attribute to its nearness to its wild ancestor – it is nevertheless vulnerable to certain problems. As I mentioned, it prefers cold to heat and wet to dry (all within reason); moreover, when stressed by either of those factors, it is doubly susceptible to insect pests and diseases. Most of those can be reduced or avoided by careful rotation, diligent cleanup of all kale (and other) crop pant residues, high humus, good soil drainage, and mulch. I have plenty of cabbage moths, but they prefer to lay their eggs in my cabbage or broccoli, where the worms are more concealed, than in kale or kohlrabi, where the looser foliage leaves them more exposed to predators.

Some people claim that when plants grow in rich humus-y soil with no nutrient stress, they are basically immune to pests. Kale both confirms and refutes that theory. Regarding diseases, it’s spot-on; regarding insect pests, it’s more right than wrong. But what about large animal pests, including humans? (You may not see yourself as a pest, but be sure the kale does.) I am not attracted to the weak, stressed plants, but rather to the robust, well-nourished ones – as are my neighbors, the deer; they’ll walk right past my more delicate broccoli and kohlrabi, but when they come to my kale, they stop right there. They start nipping at the larger, lower leaves, leaving the delicate upper leaves to size up, just like I do. Hey, they’re not stupid; only electric wire will keep them away, and that only with attentive maintenance; leave the power off for a couple of nights, and they’ll notice and respond.

Although the younger leaves are more tender, I generally prefer the mature lower leaves for greater yield and nutrition Since the coarse stems are tougher and less nutritious than the leaf blade, I strip off most of the latter, discarding the thicker parts of the stem and center vein. There is a downside to letting kale get overgrown: At some point the senescent foliage not only becomes yellow and inedible, but it harbors fungal diseases that can spread to the younger leaves. Therefore, as fast as the lower leaves mature, I either harvest them to eat or compost them to remove them from the area.

Fresh kale (of any “kale” species) doesn’t store very well after harvest. I used to dehydrate the chopped leaves, but now I mostly blanch and freeze it. Fortunately, thanks to its rapid growth and cold-hardiness, I can enjoy it fresh out of the garden for a few months of the year, even if I have to kick away some snow to get at it.

About the author: Will Bonsall lives in Industry, Maine, where he directs Scatterseed Project, a seed-saving enterprise. He is the author of “Will Bonsall’s Essential Guide to Radical Self-Reliant Gardening” (Chelsea Green, 2015). You can contact Will at [email protected].

Scroll to Top