Brassicas are an impressive group of vegetables.
Each year the National Garden Bureau, a non-profit organization promoting the pleasures of home gardening, selects one bulb, one annual, one edible plant and one perennial to celebrate in their Year of program. It’s a great way to discover a new plant or to learn a bit more about a plant you may already be growing.
Here is the third of the four plants honored in 2017, the brassica.
What? The word brassica doesn’t ring a bell? Yet, I’m sure you eat brassicas quite often. You see, the genus Brassica includes a host of very common vegetables: cabbage, turnip, broccoli, Brussel sprouts and many more. It’s just the name brassica that’s unfamiliar. They’re also known as cole crops, derived from the Latin word caulis for stem. You may have noticed these terms in cole slaw and cauliflower.
Four-petaled flowers are a rarity in nature, except in the Brassicaceae.
The genus Brassica belongs, not surprisingly, to the Brassicaceae family, formerly known as crucifers because the 4-petaled flowers are shaped like a cross.
Most of the species are biennials: they produce a rosette of leaves in the first year and bloom and produce seeds the second, then, their life’s role completed, they die. However gardeners usually harvest brassicas in their first year, treating them as if they were annuals. We don’t even let them bloom unless we want to harvest their seeds.
The Brassicaceae family has a global distribution, but the genus Brassica comes strictly from the Old World: Europe, North Africa, Western Asia and India. Several species, especially among the mustards, have however escaped from gardens to become weeds on other continents.
There are innumerable ways of preparing brassicas.
Brassicas can be eaten cooked or raw, even marinated or fermented (think of sauerkraut), as leaves, stems, flower buds or seeds, on their own, as condiments or incorporated into mixed salads, stews, soups and so many other recipes.
They are rich in vitamins C and K, carotenoids (precursors of vitamin A), antioxidants (especially anthocyanin), fibers, a whole host of minerals and several nutrients known to have cancer-preventing capacities, such as sulphoraphane, DIM (3,3′-Diindolylmethane) and selenium. Many of these components also stimulate an immune response against viruses and bacteria and can thus help prevent infections. Perhaps we should be saying “a cole a day keeps the doctor away”!
For these reasons, some nutritionists class brassicas among the superfoods, ones we should ideally consume every day.
The Downsides to Brassicas
But everything isn’t so rosy with brassicas. You see, they don’t necessarily smell like roses. The intense and rather disgusting odor given off when you cook many brassicas is caused by sulfur compounds, the same compounds that are so good for your health. So stinky cabbage is actually a good thing: its proves the plant is full of healthy nutrients. So pinch your nose while you cook brassicas and think about good you’ll feel when you reach 100!
There is also another point at which brassicas don’t smell much like roses. You see, humans have great difficulty digesting raffinose, a sugar found in brassicas. The bacteria in our large intestine, though, make great efforts to do so and as a result that they produce a prodigious amount of odoriferous methane, resulting in flatulence. Add any sulfur particles your body didn’t digest and the resulting gas can… well, I think you can figure the rest out!
At least this problem can be solved quite readily by ingesting the enzyme alpha-galactosidase, sold notably under the trademark Beano, that does digest raffinose.
Finally, brassicas often contain glucosinolates, compounds that taste very bitter to some individuals, but seem quite mild to others. That’s why some people have a deep dislike for some brassicas! However, selection of brassicas with a less bitter taste has been going on for millennia, and they become less and less bitter with each generation. If you haven’t tasted a brassica since your childhood, maybe it’s time to try again!
Easy to Grow…
Brassicas are inevitably easy to grow. They are started by seed either indoors or out. They tend to be quite cold-tolerant and many of them do best in cool climates.
Typically, fast-growing varieties are sown indoors for a head start, allowing an early- or mid-summer harvest, while slower-growing varieties are sown outdoors in early summer as a fall crop. Many taste better after they have been lightly touched by frost. Several brassicas store very well in root cellars and were therefore staple foods in northern regions where fresh vegetables weren’t available in winter.
In countries with mild winters, brassicas are often grown as a winter crop, either for local consumption or for export. As a result, coles can be found fresh in supermarkets all year long.
You can produces sprouts or micro-greens from just about any brassica.
And what about microgreens and sprouts? These barely germinated vegetables can be grown year-round in your kitchen and are within just a few days of adding to a soup or sandwich. All brassicas can be used for sprouts and microgreens.
…When You Can Control Their Enemies
Floating row cover to protect brassicas
If wild brassicas have a bitter taste, there’s a reason for it: it evolved as a defense against their enemies. Not many animals, from insects to higher animals, are interested in eating them. However, we humans have messed things up a bit when it comes to the domesticated coles. We keep choosing the sweetest-tasting, least-bitter varieties over multiple generations and are slowly eroding their protection. As a result, modern brassicas have no lack of insect pests, including various caterpillars (especially cabbageworm and cabbage looper), cutworms, aphids and flea beetles. BT (Bacillus thuringiensis) can be a very effective control for butterfly larvae (i.e. caterpillars), but for others, it’s often easier to cover the plants with an insect barrier (floating row cover) at the beginning of the season. That way their enemies can’t even touch them.
The taxonomy of brassicas is complex and always seems to be changing. In researching just this article, I found Wikipedia using two or even three botanical names for the same plant (in different articles, that is). If scientists can’t figure the names out, you can expect it won’t be easy for amateur gardeners! Part of this is due to the fact that many of these plants readily cross with other brassicas: that always makes things more complicated. However, the multiple shapes different brassicas take create even greater confusion.
There are more than 30 species of Brassica, including several natural hybrids, and almost all of these plants are consumed by humans in one country or another. Human beings have however seriously modified the appearance of brassicas and most don’t resemble their original wild species at all.
Here are the species most often grown as vegetables… and the various plants that are derived from them.
Cabbage (Brassica oleracea)
Wild cabbage (Brassica oleracea oleracea)
I know of no plant that has produced as many wildly differing varieties as the wild cabbage (B. oleracea oleracea): cabbage, kale, cauliflower, broccoli, kohlrabi and many others all derive from this one plant. The odd thing is that wild cabbage doesn’t seem very promising as a vegetable to start with, what with its leathery leaves, strong smell, intense taste and very bitter flavor.
Wild cabbage is a biennial and produces in its first year a large rosette of blue-green leaves, a coloring which comes from a thick coating of white wax. The wax serves to protect them from salt mists, as wild cabbage commonly grows on seashores in southern and western Europe. The second year, the plant produces a flower stalk up to 7 feet (2 m) tall and thousands of pale yellow flowers.
When and where wild cabbage was first domesticated is lost in the mists of time. It is quite possible that it was domesticated several times in different regions of Europe, starting about 1000 BCE. There is no doubt that the ancestors of both the Greeks and the Romans grew some sort of cabbage, but it seems to have been unknown to the ancient Egyptians.
Portuguese kale (Brassica oleracea sabellica). Photo: National Garden Bureau
Kale (B. oleracea sabellica), also called leaf cabbage, appears to have been the first cabbage to be domesticated by humans, at least about the fifth century BCE. Early farmers knew nothing about genetics and hybridizing, but they were smart enough to keep the seeds of the very best plants to sow the following year, gradually turning wild cabbage into kale.
Kale has larger, thinner and more digestible leaves than wild cabbage, and produces them on an erect and edible stem rather than a rosette, making harvesting easier. Very quickly, a curly-leaved mutation became popular because it produced a greater leaf surface and therefore more to eat in less space and it remains the norm for kale to this day.
Today’s kale generally remains fairly strongly flavored and is considered the best brassica for human health. Its taste improves if you wait until it gets a good fall frost before you harvest it.
Lacinato or black kale, also known as dinosaur kale.
One very old dark-leaved strain of kale, originally called black kale, Tuscan cabbage or Lacinato kale, has been renamed dinosaur kale by foodies, because its bumpy leaves are said to resemble what dinosaur skin is thought to have looked like. You might want to use that term when you introduce the stronb-flavored vegetable to your kids!
Jersey kale (Brassica oleracea palmifolia). Photo: Rare & Exotic Seeds
The strangest cabbage is undoubtedly Jersey kale or cow cabbage (B. oleracea palmifolia), an extra-tall variety of kale. In climates where winters are very cool but frost free (it will not thrive where it is hot all year), it will grow all year and can reach up to 20 feet (6 m) in height! The lower leaves are typically harvested to feed livestock (hence the name cow cabbage). Then, stripped of all its leaves except those at the top of the plant, this cabbage ends up resembling a palm tree! After it blooms, the stems are cut and dried to make walking sticks. In colder climates, it remains much more compact and you won’t be able to make much of a walking stick out of it.
Collards (Brassica oleacea viridis)
Collards or collard greens (B. oleracea viridis) are another primitive type of cabbage, that is to day, close to wild cabbage. In that way, they are very similar to kale which they closely resemble, except for their smooth, flat leaves. Indeed, collards and kale can be used interchangeably in recipes. As with kale, collards do not form a head, but rather an upright stalk. They’ve been grown for at least 2,000 years and are especially popular in areas with hot climates, as they seem more heat tolerant (and less cold resistant) than kale.
Headed cabbage (Brassica oleracea ‘Hercules’). Photo: National Garden Bureau
Cabbage or headed cabbage (B. oleracea capitata), with its densely-packed, rounded head, is so well known that most people probably assume this is the natural shape for a cabbage plant. In fact, wild cabbage has an open rosette, nothing like a the rounded center of head cabbage. It was gradually selected from wild cabbage by choosing plants with a tighter terminal bud as they took up less space in the garden. This resulted in a plant with a dense head, very close to modern headed cabbage.
Headed cabbage became popular in Rome about the 1st century BCE and the Romans distributed it throughout their empire. It gave rapidly way to variants still cultivated today: white cabbage (B. oleracea capitata alba), with smooth green leaves, red cabbage (B. oleracea capitata rubra) with red to purple leaves and cone cabbage (B. oleracea capitata acuta) with a pointed head. The less densely headed, crinkle-leaved Savoy cabbage (B. oleracea capitata sabauda) came later, in the mid-16th century.
There are green and purple kohlrabis (Brassica oleracea gongylodes).
Kohlrabi (B. oleracea gongylodes) was also gradually developed from kale by choosing plants with less fibrous stems than normal. The form we know today, with a completely rounded stem often mistaken for a bulb, was already known in Germany in the 1st century BCE. The name kohlrabi comes from Swiss German and means cabbage turnip.
Broccoli (Brassica oleracea italica ‘Belstar’). Photo: National Garden Bureau
The first cabbages to be grown as annuals for their edible flowers appeared between the second and sixth centuries, but broccoli (B. oleracea italica) as we know it today was developed in Italy sometime around the 16th century. Green and purple varieties are available, with dense or open heads, the latter called sprouting broccoli.
Modern cauliflower (Brassica oleracea botrytis) comes in all sorts of colors.
Cauliflower (B. oleracea botrytis) is also an annual cabbage cultivated for its dense flower head. The head is called a curd, due to its whitish coloration and its texture, said to ressemble cheese curds. Cauliflower is harvested at an earlier stage than its cousin, broccoli, when its flower buds are still very immature. Plants similar to cauliflower date back to the 6th century. Originally cauliflowers had to be blanched, that is, their leaves were tied over the curd to keep the sun off and this maintain its white coloration, but most modern cauliflowers are self-blanching: they need no special treatment to give white curds.
There are also purple, green and, more recently, orange cauliflowers (the latter was first found as a single plant in a field in Canada in the 1970s).
Romanesco cabbage, with spiral green florets, is also a form of cauliflower.
Brussels sprout (Brassica oleracea gemmifera)
The last well-known cabbage to be introduced was Brussels sprout (B. oleracea gemmifera), which, of course, came from Belgium and was introduced towards the 16th century. This plant produces the tall stems and large leaves of kale, but with rounded buds like tiny headed cabbages emerging from the leaf axils. There are both green and purple forms of Brussels sprouts.
Ornamental cabbage (Brassica oleracea acephala)
The last cabbage I’ll present here is ornamental cabbage (B. oleracea acephala), a non-heading cabbage. Under the influence of cool autumn days, its leaves change color to pink, red, white or multiple colors. It is usually grown in flower gardens as an ornamental plant for fall color. Despite its unusual colors, ornamental cabbage is perfectly edible and chic restaurants often use their surprisingly colored leaves in dips and salads.
But those aren’t the only cabbages around: there are many more types that are less well-known, either old varieties largely abandoned by modern gardeners or ones grown only very regionally. Some others you may hear of, all derived from wild cabbage, are gai-lan (kai-lan or Chinese broccoli), marrow cabbage, perpetual kale and broccolini.
Mustard greens (B. juncea)
‘Black Knight’ mustard greens (Brassica juncea ‘Black Knight’) Photo: National Garden Bureau
Brown mustard is the name for both the wild plant and the condiment derived from the seeds of B. juncea. As a vegetable, it has many other names, including mustard greens, Chinese mustard, leaf mustard, Indian mustard and tatsoi. It’s a biennial grown as an annual and resulted from a spontaneous cross between black mustard (B. nigra), source of the popular condiment we call mustard, and field mustard or rapeseed (B. rapa). Originally from Asia, the various leaf mustards are popular in Oriental cuisine. It can have green leaves, purple lesaves, broad leaves, narrow leaves, frilled leaves or even form a head like cabbage.
Mizuna (B. juncea japonica), with green or purple leaves, is the Japanese form of this vegetable.
Turnip (Brassica rapa rapa ‘White Lady’). Photo: National Garden Bureau.
Turnip (B. rapa)
In spite of its rather inauspiciously thin root, it was field mustard (B. rapa oleifera) that gave birth to the plant we call turnip or white turnip (B. rapa rapa). Turnip is a biennial of European origin and is grown for its bulblike root, although its foliage is also edible. Its flesh is white as is its skin, except for the top part that can be reddish, purplish or green where it is exposed to the sun
Bok chou (Brassica rapa chinensis), left; Chinese cabbage (Brassica rapa pekinensis), right.
While ancient European farmers worked on turning field mustard into a root vegetable, in the East, B. rapa took a very different turn, evolving by human selection into a leaf vegetable. Over the centuries, this gave almost as wide a variety of vegetables as cabbage (B. oleracea) did in Europe. The best-known Oriental vegetables derived from field mustard are are bok choy or pak choy (B. rapa chinensis), with swollen green or white petioles, and Chinese cabbage or napa cabbage (B. rapa pekinensis), with a dense oblong shaped head.
Yet another form is rapini or broccoli raab (B. rapa rapifera), a European vegetable that looks a lot like sprouting broccoli, but with a stronger taste.
Rapeseed (B. napus)
A field of rapeseed (Brassica napus)
It is hard to believe that rapeseed, also called oilseed rape or simply rape, a slim annual oil-producing plant with yellow flowers and scrawny roots, could possibly be derived from the same species as rutabaga, a biennial with an extremely large swollen edible root, yet they are both variants of the same wild mustard plant: B. napus.
This species is a natural hybrid, resulting from a spontaneous cross between cabbage (B. oleracea) and field mustard (B. rapa). The striking difference between the two plants comes from the fact that the second parent of rapeseed was the annual form of the plant, field mustard (B. rapa oleifera), a forage plant also grown for its oil-rich seed, while the second parent of rutabaga was the turnip (B. rapa rapa), the biennial form of field mustard with a distinctly swollen root.
It would appear that, of the two plants, rapeseed was the first to be cultivated, as European farmers have been growing it since at least since the 15th century.
Originally, rapeseed was strictly used as animal fodder and its oil, for industrial purposes, as it was too bitter for human consumption and, in addition, contained a great deal of erucic acid (up to 54%), which can be toxic if consumed in large quantities. However, in the 1970s, Canadian researchers succeeded in developing a non-bitter, low erucic acid (less than 2%) rapeseed, opening the way for its use in human food. Judging the name “rapeseed oil” unappealing and unmarketable, though, they gave this new lineage the name canola, for Canada oil. Canola oil has since become the third-leading source of vegetable oil in the world, after soybean and palm oil.
Note though that nearly all canola produced in North America has been genetically modified to make it resistant to herbicides, a modification considered unacceptable by the organic community.
‘Laurentian’ rutabaga (Brassica rapa rapifera ‘Laurentian’) is the classic rutabaga grown in North American gardens.
Rutabaga (B. rapa rapifera, syn. B. napobrassica) is a biennial resulting from the aforementioned cross between cabbage (B. oleracea) and the biennial root vegetable turnip (B. rapa rapa). Apparently this spontaneous hybridization either took place or first gained notice in 17th century Sweden, as not only does the name rutabaga comes from Swedish (it means, quite logically, “cabbage turnip”), but the other common names, Swedish turnip, swede turnip or simply swede, all link back to that country. In some areas, it is known as neep, from an old word for turnip.
Rutabaga is a vegetable or forage crop with a thick, purple-topped, rounded white or yellow root (although yellow rooted strains are considered superior for human consumption) and edible leaves. It looks very much like an extra-large turnip and many people do confuse the two. To distinguish the two, turnip has a smaller root and white flesh.
Rutabaga is a popular vegetable in Northern Europe and North America, but not so much in southern Europe, where people often consider it a starvation food or grow it mainly as animal fodder.
Give Brassicas a Try!
The renewed interest in kale, which today’s foodies see as a miracle food, plus curiosity about Oriental vegetables, so many of which are brassicas, has stimulated a renewed interest in the various brassicas over the last few years. Try growing a few in this summer’s vegetable garden (You’ll find them in many of the seed catalogs listed here): you just might make some surprising discoveries!