Growing Plants from the Cabbage Family
by Don Janssen, Extension Educator
Cabbage family plants usually grow and yield better when planted for a fall harvest. Transplants can be hard to find in midsummer, but they’re easy to grow from seed in the garden.
Cabbage and kohlrabi grow well during the heat of the summer. But broccoli, cauliflower and Chinese cabbage do best in cool weather, so they can be planted in midsummer. Brussels sprouts have a long growing season, so they’re planted in May but not harvested until after frost.
To grow your own transplants, sow seed directly in the garden in June. Seed will germinate quickly in the warm soil. Mark rows carefully so you don’t accidentally till the seedlings under or mulch over them. Be sure to identify each crop, also -- seedlings of the various crops can be difficult to tell apart.
When seedlings reach the four- or six-leaf stage, they are ready to be transplanted. Space kohlrabi 8 inches apart; broccoli and Chinese cabbage 12 inches apart, and cauliflower 24 inches apart in rows 18 to 24 inches apart for kohlrabi and 24 to 30 inches apart for the others. A high-phosphorus starter fertilizer will help them get established quickly.
The biggest problem in growing these crops is usually insect pests. Cutworms may nip transplants off at or just below soil level and root maggots may attack young plants. By far the most common problem, however, is cabbage worms and other caterpillars. They feed on foliage as well as the plant parts that gardeners hope to harvest. What they don’t chew holes in they contaminate with their droppings. Hand picking is one approach to caterpillar control. Appropriately labeled chemical insecticides can also be used. A non-chemical alternative is sprays of Bacillus thuringiensis, a bacterial disease of caterpillars that’s formulated and sold as a pesticide. It needs to be reapplied after rain or overhead irrigation but can be used right up to harvest.
Regular watering during dry weather and a nitrogen sidedressing four to six weeks after transplanting are basic requirements for all the cole crops. Cauliflower must also be blanched to keep the sun from discoloring the developing curd (the white, edible part) and causing off-flavors. Self-blanching varieties have vertical leaves that shade the head; others must have their leaves tied around the heads as soon as the heads become visible.
To promote even development of Brussels sprouts, pinch out the growing tips of the plants after sprouts have formed along the stems. If you don’t, you usually end up with a few large sprouts toward the bottom of the stem and a lot of little ones toward the top. To give sprouts more room to grow, twist off the lower leaves.
Kohlrabi is ready to harvest when the bulbous stems are 1 ¾ to 2 inches in diameter. Some varieties get woody if they grow much larger than that; others are said to maintain eating quality at larger sizes. When in doubt, harvest early.
Broccoli is ready to harvest when the heads have reached maximum size and before they open to form little yellow flowers. Side shoots will form smaller heads -- you can harvest these, too. Cauliflower is ready to harvest when heads are about 6 inches in diameter. In hot weather, heads will reach this size only three or four days after blanching; in cool weather, it will take a week or two. Heads left covered too long, especially in hot weather, will quickly rot.
Harvest brussels sprouts from the bottom up. They’ll have better flavor if they’re left on the plants until a frost or two has occurred. Cabbage, too, is better if allowed to mature past the first frost.
Chinese cabbage can be harvested anytime. Young leaves make an excellent salad vegetable or stir-fry ingredient. Mature heads should be harvested when they are fairly solid but before the upper leaves turn yellow.
University of Nebraska-Lincoln Extension in Lancaster County is your on-line yard and garden educational resource. The information on this Web site is valid for residents of southeastern Nebraska. It may or may not apply in your area. If you live outside southeastern Nebraska, visit your local Extension office