Radishes, kale, arugula, and broccolini from the garden are spicing up our salads this spring. These ‘Brassicas’ share a plant family (family Brassicaceae) with other nutrient-packed veggies, including broccoli, cauliflower, bok choy, turnips, collards, cabbage, cress, mustard (seed and greens), and many more. Originally named ‘cruciferous vegetables’ for their flowers’ four-petaled, cross-like shape, these plants have long been nurtured by gardeners around the world. Foods ranging from sauerkraut to Asian stir-fries to stewed collard greens reflect the widespread popularity of Brassicas.
While Brassicas continue to influence our cuisine, gardeners and farmers historically altered the very evolution of these prized edibles. A sub-group of the Brassicas, the cole crops, have all been traced back to the same ancestor species, a wild cabbage from the Mediterranean. Gardeners saved and replanted the seeds from their favorite cabbage plants, resulting (over many generations and in many locations) in plants never seen before in nature: enlarged, edible leaves in cabbage, kale, and Brussels sprouts; swollen stems in kohlrabi; and delicious flowering stems in cauliflower and broccoli.
Ancient gardeners had discerning taste: every part of Brassicas are packed with nutrients. Their distinct, mustardy flavor is due to the presence of compounds called glucosinolates, which fight cancer. Various studies have found lower rates of cancers in groups of people that eat more Brassicas, and there are several biological pathways resulting from glucosinolate digestion that prevent or interrupt cancer. Brassicas are also rich in vitamins, minerals, and antioxidants that promote cardiovascular health and lower blood pressure.
But while they are one of the most nutritious foods, Brassicas are unfortunately not everyone’s favorite vegetable. In North America, approximately 70% of white adults are sensitive to the bitter taste of even low concentrations of glucosinolates. In India, this sensitivity affects approximately 60% of the population, while in western Africa around 97% of the population is affected. Glucosinolate sensitivity is genetically determined and fades with age; preschoolers with this sensitivity are generally repulsed by broccoli, while those without enjoy the flavor. My preschool-aged children and I adore Brassicas, making it highly likely that we are genetically programmed to only taste glucosinolates at very high concentrations.
Why do the majority of people carry genes that, at least in youth, make a highly nutritious food taste disgusting? One hypothesis links glucosinolates, iodine deficiency, and thyroid disease. When people don’t eat enough iodine (available in seafood, dairy, and iodized salt), excess glucosinolates may increase the likelihood of thyroid disease and goiters. Sensitivity to the taste of Brassicas may have improved survival rates in areas where iodine in the food supply was low, giving an evolutionary advantage to pickier eaters. However, assuming you’re not iodine deficient, the consensus is that eating one to two servings of Brassicas daily is a healthy choice and not at all a risk to your health.
Boiling Brassicas removes many of their nutrients, but stir-frying for 3-5 minutes or steaming for 2 minutes are effective cooking methods that retain the majority of nutrients. Freshly picked, raw Brassicas likely provide the highest levels of cancer-fighting glucosinolates, as these compounds begin to degrade in storage. Grow them in your garden for a fresh supply.
Unfortunately, Brassicas often make trouble for gardeners. They attract aphids and flea beetles like magnets, wilt at the first sign of dehydration, bolt as soon as the temperatures rise, and can even prevent following crops from germinating.
To minimize insect damage, rotate where you plant Brassicas each year, and grow them in the spring, fall, and winter (they tolerate colder temperatures than insects). Usually, I plant arugula and radishes in March and harvest them before the aphids are abundant. Kale, broccolini, and collards stay healthy here until July or early August, when heat stress and aphid damage conspire to end their season. Floating row covers may provide some protection from cabbage worms and flea beetles.
I’ve given up on cauliflower and broccoli after disappointing, aphid-ridden harvests in our hot, dry summers, but there are plenty of other delicious options. Broccolini, which provides a continuous harvest of small, broccoli-like florets and stems, gives me a more predictable supply of florets than broccoli. Kale withstands some heat as well as cold and provides a several-months to multiple-year (depending on the climate), as-needed harvest. Radishes and arugula are the sprinters of the garden, ready to eat within a month of planting in ideal growing conditions, although neither tolerates heat well.
Brassicas love cool, moist weather and become delightfully sweet after a few freezes. Kale, arugula, collards, and bok choy survive our Idaho winters buried in straw or sheltered in an unheated hoop house. I plant a spring crop of Brassicas 6-8 weeks before the last frost date and a fall crop in early September, some of which I overwinter.
If you missed the spring planting season this year, try planting a fall crop and overwintering Brassicas for some nutritious and possibly (depending on your genes and your age) delicious eating.
Singh, J., Upadhyay, A. K., Prasad, K., Bahadur, A., & Rai, M. (2007). Variability of carotenes, vitamin C, E and phenolics in Brassica vegetables. Journal of Food Composition and Analysis, 20(2), 106-112.