All About the Brassicas

I started my blog months ago and I’m well on my way to winning the Pulitzer Prize for Blogging. Okay, not really. I’ve had a tremendous case of writer’s block. I even asked my friends what they would like for me to write about. “How about soup?” or “What about cheese?” Those are fine ideas, but the spark simply wasn’t there for those topics at that moment. I have some good news, though. There has been a spark! What is the topic that has finally ended my months-long hiatus from this forum? Brassicas.


What is a Brassica?

Let’s begin by talking a little bit about taxonomy. Remember kingdom, phylum, class, order, family, genus, and species? This may not be something you’ve thought about since 10th grade biology class, so consider this a quick review. We’ll start at the family level. Brassicaceae (formerly known as Cruciferae) is commonly known as the “mustard family.” People also refer to this group as the “cruciferous vegetables.” It’s made up of 340 genera (plural for genus), which collectively include 340 species. Brassica is the genus of interest for this discussion.

There are three species within this genus that are of great significance to humans because they account for a tremendous amount of food that is eaten all over the world. Brassica oleracea, whose common name is wild cabbage, is the European variety. Brassica rapa includes a number of Asian cultivars. Brassica napus resulted when B. oleracea and B. rapa hybridized naturally. This plant is believed to have originated in Mediterranean Europe, but it’s now grown worldwide.

Before we move on, it’s important we address some additional terminology. A cultivar is a plant that is the result of artificial selection. I’ll use a non-plant example to explain. Domestic dogs are from the species Canus lupus. The breeds that we’re familiar with are the result of artificial selection because we chose the characteristics that we found appealing. In the plant world, rather than refer to these plants as breeds, we call them cultivars. Varieties, on the other hand, are species or subspecies that have arisen in nature when two closely related species reproduce and form viable seeds. That’s what happened in the case of B. napus.


Some of your favorite foods may be cultivars or varieties of B. olercacea. Kale may have been one of the first brassicas to be cultivated, going all the way back to ancient Greece. White and red-headed cabbage, savoy cabbage, cauliflower, broccoli, and kohlrabi are also members of this group. Some research has suggested that the white head present in cauliflower is actually a genetic mutation!

While B. rapa likely grew alongside B. olercacea within the Fertile Crescent, it was this B. rapa that took hold in Asia. Pak choi is thought to be the most ancient cultivar, going back to the 5th century. Korean gardeners likely cultivated the first Chinese cabbage. This plant spread to Southeast Asia by the 15th century, but it wasn’t until the 19th century that this popular food made its way to the gardens of Japan.

The other important member of the genus Brassica is B. napus. One cultivar of this group may show up on your dinner plate - rutabaga. However you are more likely to cook with this plant as its primarily grown as a source of vegetable oil. That oil is not only designated for cooking, but it’s also used to produce biodiesel.

The Beauty of Brassicas

Aside from endless culinary possibilities, which we will touch on later, there are many reasons to incorporate these plants into your diet. Brassicas are rich in fiber, minerals, and folate. They are also a good source of vitamins C, E, and K. Those vitamins, along with the carotenoids, are antioxidants. Through both natural and environmental processes, molecules referred to as “free radicals” are present in our body. These substances can cause cell damage. Research has shown that antioxidants can offset the activity of those free radicals.

Brassicas also contain a group of chemicals known as glucosinolates. These sulfur-containing compounds are a source of brassica’s bitter flavor and distinctive odor. More importantly, when we digest these substances, they break down into other compounds which have gotten quite a bit of attention from scientists. One substance in particular, isothiocynate, has been studied extensively for its anticancer effects. Studies have also suggested that this compound may reduce inflammation and help prevent diabetes. As if that weren’t enough, brassicas also possess antibacterial properties that have been shown to help patients dealing with H. pylori, the bacterium responsible for stomach ulcers.

Of course no food can be without some sort of controversy. A quick web search will reveal articles warning you about the dangers of eating too much kale. What’s that all about? First, as stated earlier, brassicas are a great source of vitamin K. One of its functions is to assist in clotting. For individuals on blood thinners, this could be problematic... if they consume exorbitant amount. So while it’s unlikely that someone could eat enough kale to interfere with their medicine, someone who is taking blood thinners may want to ask their doctor or a registered dietician for advice. The other problem is associated with a group of compounds known as goitrogens. These chemicals can affect the uptake of iodine by the thyroid gland, which is responsible for producing hormones that regulate our metabolism. Individuals with hypothyroidism are at greatest risk, but again, this would require someone to eat a ridiculous amount of raw kale (or other brassica). The good news for anyone who is worried about this is that cooking will deactivate the enzyme that causes goitrogen to interfere with iodine.

Grow Your Own Brassicas

urban gardening
Early Summer, 2020

Gardening season is just around the corner and that was the real spark for this entire blog. I pulled out my box of seeds and as I was taking inventory, I realized just how many things I plant belong within the Brassicaceae family. In addition to the plants I mentioned above, turnip, radish, watercress, arugula, and mustard greens are also close cousins. I have been growing a number of these wonderful vegetables and leafy greens over the years. I would like to share some things I’ve learned along the way. I’ve had greatest success sowing my seeds directly in the ground, rather than starting them in trays or pots. The seeds prefer a soil temperature between 65-75 degrees F. On the cooler side, it may take 7-10 days for the seeds to sprout. Under ideal conditions, I’ve seen them pop up in as little as 3 days! The seedlings tend to be fairly hearty compared to other types of vegetables that I grow. They need partial to full sun and enough water to avoid drying out.

For leafy varieties, such as kale and pak choi, the wait for edible leaves is around 2 months. While it’s not necessarily instant gratification, this relatively quick turnaround time is one of the things I love about growing them. Broccoli, cauliflower, and Brussels sprouts are a different story, however. Growing your own is tasty and rewarding, but you’ll be waiting almost twice as long before you can claim the prize. Those plants also take up a lot more space, which can be problematic for those of us with limited gardening space.

While brassicas are often labeled as “cool season crops,” it’s possible to have brassicas throughout the entire growing season. One of the keys to success is to get them established early so that you are guaranteed a spring / early summer crop. With careful seed selection, you can plant cultivars that are slow to bolt (or go to flower) when it starts to warm up. If it’s an especially hot summer or you live in a very warm climate, even your best efforts may not guarantee an uninterrupted supply of brassicas. Fortunately, you can start your second crop in early August and enjoy these delicious plants well into late fall.


backyard gardening
Fun Jen has a special place in my heart

I have a few favorite sources that I turn to when purchasing brassica seeds. Kitazawa Seed Company is my go-to for Asian varieties. They have a tremendous selection and their seeds are of great quality. I had one packet from 2014 that produced beautiful plants until I finally used up the rest of the seeds last season. When I want to grow something a bit more unusual, I turn to Botanical Interests. They specialize in heirloom and interesting varieties that I have not seen in other catalogs. For everything else, I turn to Johnny’s. I have had so much success with all of their seeds, no matter what plant group they are from.