Successfully Growing Brassicas
Brassicaceae is a plant family with popular spring garden members including broccoli, kale, collards, radish, and cabbage.
By Brigitte Zettl
[This article was first published in The Gateway Gardener April 2016]
Brassicaceae is a plant family with popular spring garden members including broccoli, kale, collards, radish, and cabbage. Brassicas are super foods high in vitamins, minerals, fiber, and the cancer-fighting sulfur compound isothiocyanate.
Avid gardeners must take care to meet the special requirements of brassicas, or risk disappointment at harvest time! Species in this family generally have high nutrient requirements, and are quite susceptible to pests. As with any cool-season crop, timing is important since they languish and bolt under the strain of high mid-summer temperatures. Despite being a bit more challenging to grow, their nutritional value and excellent flavor make brassicas an indispensible addition to a proper vegetable garden!
The spring planting window for this family is from mid-March though late April when daytime temperatures average 50 degrees. Use transplants in the garden where possible, since mature plants have a better chance for survival. Root crop brassicas like turnips are the exception, and seeds are sown directly into the garden. Heading and crowning species like cabbage and broccoli prefer full sun, while the leaf and root cole crops such as kale and turnip develop well in part or full sun. All benefit when shaded from western exposure. To transplant, harden off for several days, then bury stems below the soil line up to just below the bottom of the first leaves. Space appropriately, leaving 12”-24” between plants depending on the species. After transplanting, water well and cover plants immediately with floating row cover.
Compared to many vegetables brassicas are heavy feeders. They require fertile growing medium rich in organic matter, which can be achieved by amending garden soil with compost. Three weeks after planting, top-dress the soil around plants with granular organic fertilizer. Follow up every 3 weeks with a liquid organic fertilizer such as fish emulsion. Broccoli and cauliflower especially are not likely to form crowns without a strict fertilization schedule. 1”–1.5” of water should be applied weekly by drip irrigation.
Row cover goes a long way toward avoiding a pest invasion, especially from flea beetles. Cabbageworms are the most pervasive brassica pest. White moths hatch solid green caterpillars that chew large curved holes in the leaves. Once present these are sprayed weekly with a Bacillus thurgenensis product to control. Aphids tend to be a minimal problem for healthy mature plants. Spraying them with soapy water while brushing them off with your fingers and holding back on fertilizer applications reduces populations. Harlequin beetles are a more serious threat. Watering the soil with neem or spraying the ground with Beauveria bassiana spores early in the season kills beetles in their larval stage. If adults are present the only thing to do, provided you don’t want to slowly kill yourself with synthetic pesticides, is pick them off by hand and drop them into soapy water. Wireworms can ruin brassica root crops, and mustard is interplanted as prevention. If overhead watering is avoided and spacing allows good airflow, diseases are not likely to trouble these plants. If fungal infection does occur, spray plants with baking soda and water, neem, or horticultural oil.
Brigitte Zettl is a horticulturist, farmer & herbalist working to facilitate civic sustainability with botanical medicine and agricultural education. She is the founder and manager of Crown Valley Organics.