Beyond Broccoli Part Two: What’s Up with Brassicas?

Welcome back to Beyond Broccoli! Last month I posted about how the genus Brassica is classified and grouped, and where the plants come from in the world. Now let’s talk about what characteristics the brassicas have in common. Here’s some of what they share as a group:

  • An origin in temperate regions. These species originated in Europe and Asia, and most of them prefer to grow in cooler weather.
  • Thousands of years of cultivation and breeding. They’ve been part of humanity’s diet for a long time, and have great cultural significance in many regions.
  • Some physical similarities. I mentioned the cross-shaped (cruciferous) flower in the last post. Brassica seed leaves (cotyledons) have a characteristic heart shape, and seeds are generally small and round. We’ll explore leaf pigments and other commonalities in later posts.
Seed leaves of mustard
  • Life cycle. Many brassicas are biennials (producing seed in their second year), though some are also annuals or perennials.
  • Ease of cross-pollination. These plants mix it up! If they go to flower and insect pollinators have access to them, the resulting seed may produce hybrids within species or even across species.
  • Many edible parts. Brassicas have been bred to emphasize particular plant parts (leaf, stem, root, flower bud, etc.) but that doesn’t mean that other parts can’t be eaten. Go ahead and nibble on kale flower buds or cook your broccoli leaves.

Brassicas also attract the same insect pests (which we’ll talk about next time) and they share chemistry and nutrient content. These two facts are not unrelated, of course—you might not think you have the same taste in food as caterpillars, but the glucosinolates that give brassicas that characteristic bitterness appeal to us both. Or rather, the plants evolved those compounds to scare us off eating them, but the caterpillars then evolved to like them after all, and humans… well, maybe we’re just weird and stubborn.

The degree of bitterness varies a lot between brassica species and subspecies, and some people are more sensitive to bitter flavors than others. But nearly everyone can find a brassica they like to eat—and you should, because as well as being tasty, they are very good for you. Research indicates that these plants have anti-cancer properties, derived from those same glucosinolates. Brassicas also provide good doses of vitamin C, vitamin A precursors, vitamin K, folate, fiber, vitamin E, and antioxidants. Raw or minimally cooked vegetables provide more nutrients than those that have been cooked a long time, though any brassica is a healthy one. But there will be some variance in benefits depending on your own genetics and the conditions under which the plants were grown.

And yes, before you ask—they do cause gas. Blame those glucosinolates again for the flatulence and the unpleasant sulfurous odor. Remember they’re good for you, I guess? And that normal amounts of windiness may mean you have a healthy gut microbiome. To cut down on effects, cook the vegetables longer, don’t eat too much at once, and don’t combine with other gas-producing foods such as beans. (Or go out to weed the garden after dinner!)

Growing brassicas is not difficult, as long as you follow some basic guidelines. First of all, remember that temperate origin, and don’t plant your cabbage in May with your tomatoes! A few brassicas will keep chugging along even in summer heat, but most of them dislike high temperatures and humidity, so they are best grown in the spring or fall. Consult our resources for more information on growing schedules.  It’s also possible to put your plants into the garden too early; temperatures under 40 degrees F can adversely affect how a plant forms and matures even if it doesn’t actually freeze. And while mature brassica plants often tolerate cold temperatures just fine, seedlings can be killed by cold snaps. You can protect them with a heavier-weight floating row cover.

Should you grow brassicas in spring or in fall? It really depends on the particular plant—some do better in one season or the other—and on weather factors. In this region, temperature swings are more common in spring, which is hard on young plants, but rainfall is more consistent (so less watering). The gradually cooling temperatures of fall can be great for keeping plants growing and producing for a long time (and frost often makes the harvest taste sweeter), but it can be difficult to get them started in the heat of late summer.

Since climate change is making our spring weather more variable and the chill of autumn hit later, you’ll make it easier on yourself if you choose brassica varieties that mature faster. Look for a “days to maturity” number that’s lower than the average for that crop—40 days rather than 60, for example. “Days to maturity” is usually the number of days from seeding to harvest, but for some brassica crops (broccoli, cauliflower, Brussels sprouts, cabbage, and Chinese cabbage) it means transplant to harvest. (I know, it’s confusing, but it’s one of those growing conventions.) If you’re not into indoor seed-starting, you might want to buy transplants for this list of plants, since they need a head start. But take a look at the shorter growing period for a lot of Asian greens and most kales, and consider direct-sowing those right in your garden.

If you are starting from seed, I have a helpful post about getting the timing right. It’s specific to fall growing, but you can adapt for spring (and the math is simpler).

And if you do get caught out by a hot spell and the crop bolts, remember that you can eat the whole plant, not just the part it’s marketed for.

Next time we’ll talk more about growing brassicas, including how to deal with pest issues. In the meanwhile (hint) you might want to invest in some floating row cover and put up a fence against rabbits. (Read Part Three.)

By Erica Smith, Montgomery County Master Gardener. Read more posts by Erica.

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