Welcome back to Beyond Broccoli, the brassica blog series! You can find previous entries here. In this edition we’re going to explore the plants in the genus Brassica that are grown for edible leaves.
I think the best place to start is on the shores of the Mediterranean. This is likely the home of the wild relatives of what became the domesticated forms of Brassica oleracea. They would have looked something like what we know as kale. The lineage of these wild plants is still fairly obscured, but if you want to read more about it check out this scholarly article.
The kales we grow today are actually not all one species. Most of them are Brassica oleracea var. acephala(or Acephala Group), but the super-hardy kales like Red Russian and Siberian are Brassica napus var. pabularia, related to rutabaga. Even the B. oleracea kales are amazingly varied, having been bred for millennia into forms with curly leaves, flat leaves, small or enormous leaves, leaves with blue and purple tints, the cabbagey-looking ornamental kale that landscapers plant at the corner to carry through the winter, and kale that forms stems taller than people that are made into walking sticks. (I wish we could grow that kind here, but our heat and humidity don’t agree with it. At least you can read about it.) My favorite kind to grow and eat is the blue bumpy type known as Tuscan, Lacinato, or Dinosaur kale.
I’ve never been a kale-massager, so I prefer softer leaves that could be eaten in salad but also cook up quickly. Also, remember kale chips? Still fun, even if less trendy.
Maybe kale is over now and collards are the new cool veg. I posted a couple of years ago about the Heirloom Collard Project, and I’m noticing that these varieties maintained by seed savers are starting to make their way into seed catalogs. I’ve been growing Yellow Cabbage Collards for the last couple of years, and I really like the tender pale leaves with bittersweet flavor that have held well for me in the freezer (after steaming) waiting to be put into a soup or sauteed with a little bacon.
What are collards and how are they different from flat-leafed kale? The distinction is difficult and sometimes more culturally-based than anything else, but collards have been broken out from the Acephala Group into their own Viridis Group. They tend to be both cold-hardy and hold well in the heat, though that varies depending on cultivar.
Similar to both kale and collards is Brassica oleracea var. costata, known as Portuguese kale, tronchuda, Portuguese cabbage, or sea kale (which is also the common name of another plant, Crambe maritima, also in the Brassicaceae family). Tronchuda is a decorative plant with broad white ribs in large green leaves, used for traditional soup recipes, that is not very cold-hardy but can take summer heat (up to a point). I recommend trying it if you’re an adventurous gardener!
Let’s step back for a moment and think about plant evolution. Wild leafy plants developed into the wide range of forms the Brassica genus encompasses today in two ways: natural mutation, and breeding by human farmers. What that probably meant was that people gathering or growing the plants spotted a mutated form, thought it had value, and collected the seeds to grow more of it, gradually refining the new trait. One of those traits must have been the tendency for leaves to curl in on themselves and form a head. Those heads would have been loose to begin with, and only over time and through breeding became what we now call cabbage.
There are two kinds of cabbage that have completely separate origins: the European cabbage, Brassica oleracea var. capitata, and the Asian cabbage, Brassica rapa subsp. pekinensis. Depending on your cultural background, you may regard one of them as cabbage (or choy) and the other as an interesting foreign dish, but they’re really not that different: both leafy vegetables that developed into a heading form. European cabbage tends to be more tightly-formed, with a firm head surrounded by more open leaves that spread out widely. This is a big plant, which we don’t always realize when we buy the head in the market, and needs to be widely-spaced in the garden.
There are a bunch of types (red, savoy, and green/white in various shapes). I suggest concentrating on the modern quicker-growing varieties for spring, especially those with smaller heads, and the hardy storage types for fall. The tight heads mean that caterpillars and other pests don’t penetrate to the center, but they will make a mess of the outer leaves and often the bottom of the head, so row covers are still a good idea. Heavy rains can cause the heads to split, and rollercoaster temperatures can make the plant give up and bolt before heads form. But they are very fun to grow when all goes well!
Asian cabbage, generally known as Chinese or napa cabbage (“napa” is from Japanese for leaf vegetable), is usually somewhat quicker-growing than its European equivalent, but less tolerant of cold early spring temperatures when it’s young. It may be better grown in fall. Even the types that form a strong head are still somewhat open-leafed, and pests seem to love them, so row cover is a real plus. There are a huge number of varieties, but most seed catalogs (except those that focus on Asian crops) only stock one or two. Start with these and then branch out!
Cabbages of all sorts have a vast literature of recipes attached to them, from coleslaw to sauerkraut to kimchi. It’s the ancient storage vegetable, whether you’re talking about cellars or fermentation crocks, but of course it’s also great for a quick salad or stir-fry.
I can barely touch here on the world of Asian leafy greens, from the semi-heading bok choy and tatsoi to the loose-leaf komatsuna, chijimisai, and Tokyo Bekana, a kind of Chinese cabbage that looks like lettuce.
Most of these are Brassica rapa subspecies, but senposai, a loose-leaf green with huge leaves, is a hybrid of B. rapa and B. oleracea. These plants all hybridize very easily, across and between species, so there’s always something new growing out there. I strongly suggest trying a few Asian greens in your garden, even if you didn’t grow up eating them. Most of them grow speedily, which is an advantage in our uncertain weather and changing climate, and they can be used in a wide variety of recipes. The flavors range from spicy to bland and the textures from delicate to crunchy; there’s something for everyone.
Asian “mustards” like komatsuna and mizuna are the spicier end of the B. rapa rainbow, but the term “mustard” more often applies to plants in the Brassica juncea species. There are subgroups in the species with differing origins throughout Asia. I’m most familiar with growing the broad-leafed varieties such as Green Wave and Red Giant, but there are lots of fun ones with fancy feathered leaves and combinations of colors. If you like spice in your life, throw some mustard seed in with your salad mix or grow it to its full size (which is pretty big!). Mustard is tolerant of summer heat longer than a lot of greens (or, um, purples) and it deals with chill well too.
I shouldn’t have left the world of European cabbages without touching on the weird cousin—what’s up with Brussels sprouts? Somehow I always thought this plant with a tall stem and leaves like kale, but which grows tiny cabbages in its leaf axils, must be a modern invention, but in fact it’s been grown in Europe (including but not exclusively in Belgium) since at least the 13th century. It’s just emblematic of the strange ways brassicas develop. Sprouts are not the easiest plant to grow here, because they need a long season of cool weather, but if you can get them going in late summer they will deal fine with the cold and give you a harvest in December. They are terrific roasted; do not boil them to death and they will reward you. Or slice them thin and use them in salads. Oh, and speaking of strange brassica developments: I have not grown Kalettes® but look them up for fun—they are a cross between Brussels sprouts and kale, and look exactly like what you are imagining.
Next month, Beyond Broccoli will literally start with broccoli and go beyond. We’ll be talking about edible flower buds and related structures in the genus Brassica. Back in July for our final chapter. Hope you’re harvesting some brassicas right now as we head into summer!
By Erica Smith, Montgomery County Master Gardener. Read more posts by Erica.