Welcome to “Beyond Broccoli”! In my next several monthly posts, I’m taking a deep dive into the genus Brassica and its place in our vegetable gardens. In this first installment, I’ll be exploring the classification of these plants and where they fit into the plant world.
Brassica is (logically enough) part of the family Brassicaceae, which is pretty huge, containing approximately 372 genera and 4060 species. Most of these are not common garden plants, though plenty are; examples include sweet alyssum (Lobularia maritima), honesty (Lunaria annua), and stock or gillyflower (Matthiola incana). Other notable plants in this family include Arabidopsis thaliana or thale cress, used as a model organism in many scientific studies, and Allilaria petiolata or garlic mustard, a persistent weed many of us fight back for years. One way to get rid of your garlic mustard is to eat it—it’s strong-tasting but great to mix with other greens. Many Brassicaceae plants are edible, though of course not all; always investigate before ingesting.
Strong bitter or spicy flavors are a characteristic of plants in this family, including some that aren’t in the Brassica genus but might still end up in your vegetable garden. I would discuss these in detail as well, but that would make my long series even longer! Here are some of the Brassicaceae plants commonly grown as vegetables or seasonings:
- Radish (Raphanus sativus). From the small round red ones to the long white ones and everything in between, root vegetables that add pungency to dishes.
- Horseradish (Armoracia rusticana). Another root with an even stronger flavor, used as a seasoning.
- Wasabi (Eutrema japonicum). Doesn’t grow outdoors in our climate. Expensive, so most of the “wasabi” you’ve eaten is likely horseradish dyed green.
- Arugula (Eruca vesicaria or Diplotaxis tenuifolia). Both the cultivated and wild versions of this leafy green are a great salad accent.
- Watercress (Nasturtium officinale). Another spicy green that likes its roots damp. (Garden nasturtiums, Tropaeolum majus, are part of the Brassicales order but not the Brassicaceae family. Common names are sometimes confusing!)
- Land cresses (Lepidium sativum, Barbarea verna). I discussed these in a previous post.
- White mustard (Sinapsis alba). I’ll talk about the Brassica mustards later, but this is the one whose seeds are commonly used to make condiment mustard. It’s also used as a cover crop.
Now let’s leave those other genera behind and start exploring Brassica itself. Within the genus, you’ll find several species dominating in our vegetable gardens. These include:
- Brassica juncea. The mustards, with an origin in Asia.
- Brassica napus. This species includes rutabaga, Siberian kale, and rapeseed or canola. It originated in the eastern Mediterranean and western Asia.
- Brassica oleracea. Originating in southern Europe, this species includes many common garden plants such as kale, collards, cabbage, kohlrabi, broccoli, gai lan or Chinese broccoli, cauliflower and Brussels sprouts.
- Brassica rapa. Includes Asian species such as bok choy, tatsoi, komatsuna and napa cabbage, as well as turnips and rapini.
You may have noticed two things about this list. First, some plants you may have thought of as different species actually belong together in one. That’s because Brassica oleracea, for example, began as a wild leafy plant with an edible flower bud, which was then bred by humans into lots of variable cultivated plants each featuring different edible parts. This happened with different wild Brassica species throughout Asia, Europe, and northern Africa. These plants are now described by terminology that divides species into groups, varieties, and/or subspecies, which I’ll mention when talking about each plant (for example, bok choy is Brassica rapa subspecies chinensis; kale is Brassica oleracea, Acephala group). You can look them up yourself if you want, but I thought yet another bulleted list would be kind of boring.
Another thing you may have noticed is that I listed the geographic origin of these species. I think it’s interesting to know where plants come from and how they have traveled with people around the world. It’s also fascinating to explore the genetics of these plants, which has illuminated some facts about their origins. You don’t need to know this information in detail to grow brassicas, but it does help to know who’s related to who if you’re going to save seeds, since these plants are famous for cross-pollination. Otherwise, just appreciate that scientists have looked into this and discovered things like the Triangle of U:
The plants in the corners seem to be the original Brassica species, which then crossed to create the ones on the sides. Brassica nigra, black mustard, and Brassica carinata, Ethiopian kale, are less commonly grown in our vegetable gardens today, though I have tried carinata and found it really tasty and a good variation on the European leafy greens.
The last thought I’ll leave you with, which could be explored deeply on its own, is about etymology. (That’s words; entomology with insects we’ll get to later.) The brassicas are also known as cole crops, and “cole” is a syllable that occurs over and over in the European languages naming these plants. It begins with a Latin word, caulis, meaning stalk or cabbage, and you’ll see it in the German Kohl for cabbage, as well as in kale, collard, cauliflower, and the obscure “colewort.” On the Brassica rapa side of things, you start with Latin rapum for turnip, and pick up “rabe” as in broccoli rabe, which is also known as rapini. Kohlrabi is a great word that combines both these roots and literally means “cabbage turnip.” Broccoli is Italian for “sprouts,” and “brassica” comes from a Celtic word bresic meaning cabbage.
If you speak Cantonese (which I don’t), then you know choy, which simply means “vegetable,” and shows up in the common names of many Brassica rapa plants (bok choy, choy sum, yu choy, etc.).
And the last bit of etymology is a prelude to next month’s post. Those of you who’ve been following plant classification for a while know that Brassicaceae used to be known as Cruciferae, and the plants in the Brassica genus as crucifers. This is from the Latin for “cross-bearing,” and it refers to the four-petaled shape of the flowers, which is in fact common to many plants in the family.
Next month we’ll find out more about what the brassicas have in common and how that affects how we treat them in the kitchen and in the garden. (Read Part Two.)
By Erica Smith, Montgomery County Master Gardener. Read more posts by Erica.