How to Grow Brassicas

Become a fan of the coolest crops in the garden with advice for sowing, growing and harvesting brassicas.

by Samantha Johnson
Cauliflower, cabbage, broccoli
Courtesy iStockphoto/Thinkstock
The brassica family of crops includes cauliflower, broccoli and cabbage.

In the symphony of instruments that make up an orchestra, there are strings, woodwinds, and percussion and brass instruments. In the symphony of vegetables that make up a garden, there are nightshades, legumes, cucurbitsalliums and brassicas. Just as the orchestra would be missing a vital piece of its ensemble if the brass instruments were absent, your vegetable garden would miss brassicas if they weren’t represented.

What are Brassicas?
Simply defined, brassicas are a group of vegetables, including cabbage, broccolicauliflower and kale, that thrive in cool climates, are remarkably hardy and frost-resistant and are noted for their nutritional values. However, to fully understand the dynamics of this extensive family of vegetables, you must explore the larger picture.

Brassicas are species of the Brassicaceae family (the “mustard” family), which is also interchangeably called the Cruciferae family, hence the reference terms “crucifers” or “cruciferous vegetables” for cabbages and similar vegetables. The word Cruciferae is derived from the Greek word meaning “cross-bearing,” and refers to the four-petaled, cross-like appearance characteristic of many plants in this family.

Confusingly enough, several species in the Brassicaceae family are not a part of the Brassica genus. Horseradish, arugula, watercress and radishes are all of members of the Brassicaceae family but belong to the Armoracia, Eruca, Nasturtium and Raphanus genuses, respectively.

The Brassica genus itself is further subdivided, with the Brassica oleracea species being the largest, with seven main cultivars. These include the familiar head-shaped brassicas (broccoli, cabbage and cauliflower), leafy brassicas (kale and collard greens), Brussels sprouts and kohlrabi. A second species, Brassica rapa, includes cultivars like mizuna, Chinese cabbage and turnips. Yet another species, Brassica napus, encompasses rutabaga and Siberian kale.

And if all of that information isn’t enough to make you feel like a cabbage head, toss in the fact that brassicas are sometimes referred to as cole crops and that the entire group is sometimes referred to as the cabbage family. But never fear—one delectable taste of homegrown broccoli or cauliflower and any nomenclature confusion will be quickly forgotten.

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Planting Brassicas
Brassicas are a cold-climate crop, ideally suited to regions with mild summers and moderately cool springs and autumns. Gardeners in regions with hot summers should strive for two crops of brassicas per year: an early spring crop, harvested before the temperatures peak in the summer months, and a late-autumn crop, planted mid-summer for harvest in the fall. With suitable climate conditions and careful scheduling, it’s even possible to harvest three crops of brassicas in one growing season.

“Our early spring transplants get planted the beginning of May, with all varieties of brassica crops seeded or transplanted by mid-May. We have a June 15 frost date,” says Jenny Tuckey, co-owner of EverGood Farm in northern Wisconsin, which produces organically grown vegetables. “Our salad crops are planted every week; Brussels sprouts once per season; broccoli, cauliflower and cabbage are planted every three weeks; and kohlrabi every two weeks. This allows us to continually harvest our brassica crops from early July to mid-October, with salad greens harvestable from early June to mid-October. We generally get about three crops of our broccoli and cabbage plantings.”

Rotate brassicas with other vegetable families, such as alliums or nightshades, to reduce their susceptibility to disease and insect problems.

“Crop rotation is essential for keeping ahead of pests,” Tuckey says. “At the start of the year, we try to put brassicas in their own field, which hasn’t had brassicas the year before. As we replant each week after that, we try not to put brassicas in the same bed twice.”

In terms of soil preparation, most brassicas prefer soil pH between 6 and 7. Soil quality is, of course, a major consideration.

“Like all vegetables, brassicas like good, fertile soil, but I’ve seen brassicas grown successfully in sand as long as they’re given the right amount of nutrients,” Tuckey says. “Add [fertilizer] into the beds [based] on how long the crop will be in the soil. Short-term crops need less [fertilization], and longer-term crops obviously need more. The best advice I have is to write out a plan. Then once planted, observe for insect pressure or signs of slow growth. After a crop has been in the ground for a month, more [fertilization] will likely be needed. For us, this was in the form of compost or compost tea. Brassicas taste best when grown quickly and in cooler climates.”

Keeping Pests Off Brassicas
For all of their glorious attributes, brassicas are plagued by one major problem: a widespread susceptibility to pests and disease.

“Brassicas are heavily hit by pests and are probably [the] most bug-prone vegetables at the farm,” Tuckey says. These pests include a range of cabbage worms (such as cabbage loopers) and aphids. Cutworms, borers, beetles and maggots also occasionally damage brassicas.

Thankfully, there’s a proven method for diminishing the effects of insects: floating row covers. Frequently used to minimize pest damage to brassica plants, floating row covers are an ideal method for deterring insects without the use of pesticides. Another important benefit of row covers is that they often produce plants with larger vegetables than their non-row-covered counterparts; however, row covers tend to slow the plants’ maturity due to lack of sun.

“We cover the longer-term brassica crops with Agribon (a breathable fabric row cover) on the day of planting,” Tuckey says. “The cover is only taken off to weed and to harvest or when the plant gets too big for the hoops. Our goal is not to eliminate pests, but to work around them and hopefully create an environment where natural predators can help us, as well. There is always some loss due to insect pests in organic farming, and we plan for this. We did have cabbage worms on our longer-season brassicas but found they did less damage because they were not able to find the brassicas until we removed the row covers. At this point, the plants were large enough to handle the pest pressure.”

Tuckey also credits proper timing with a reduced incidence of insect damage to her brassica crops.

“Getting the crop in and out quickly to beat the insect life cycle is important. We plant and harvest most of the salad brassica crops within four weeks and only take one cutting off these crops when insect pressure is high. We make sure to remove as much plant residue as possible to help with pests, as well.”

Such a remarkable family of vegetables deserves a prominent place in any garden. Choose a few brassica varieties and get growing. A symphony of garden joy awaits!

Brassica Crop Profiles
With so many brassicas at your fingertips, where’s the best place to begin? Click below to get a quick overview of the most familiar members of Brassica oleracea.

About the Author: Samantha Johnson is the author of several books, including a forthcoming book on gardening for children. She raises purebred Welsh Mountain Ponies in northern Wisconsin.

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