Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu
Consumer trends show an increase in consumption of Brussels sprouts offering potential market opportunities for Delaware growers. Brussels sprouts have been grown successfully on a commercial level in Delaware in past years. Most East Coast production currently is centered on Long Island in New York.
Brussels sprouts are in the cole crop group (Brassica olearacea var. gemmifer) and are closely related to cabbage, cauliflower, broccoli, kohlrabi, collards and kale. Brussels sprouts require a long growing season and are best grown as a summer planted and fall harvested crop in Delaware. Sprouts that are produced during hot periods will be bitter, therefore spring planting is not recommended.
Recommended varieties for our region include Dimitri (105 days) and Jade Cross E (85-97 days, our standard). Varieties for trial include Royal Marvel (85 days), Churchill (90 days), and Franklin (100 days). Nautic (120 days) and Diablo (110 days) are late varieties for extended fall harvest.
Brussels sprouts can be grown as transplants in 72-128 cell flats or can be field seeded in transplant beds for bare root transplants. Transplants should be started in May or early June and then field transplanted from the third week in June to the second week in July. Long season varieties should be planted by the end of June. Use shorter maturing varieties for later plantings. Brussels sprouts are transplanted in the field at a spacing of 36″ between rows and 15-24″ in the row. Double rows on white plastic mulch with drip irrigation is an option.
Brussels sprouts require 100-150 lbs/A of nitrogen split with 50-75 lbs/A at planting and the remainder as sidedressings. Apply 25-40 lbs/A of sulfur with nitrogen preplant applications and include 1.5-3.0 lbs/A of boron per acre and 0.2 lbs/A of molybdenum per acre as micronutrients.
Irrigation is required, with particular attention needed in summer months to achieve the equivalent of 1 inch of water per week during July, August, and September.
Herbicides for weed control in Brussels sprouts are limited compared to other cole crops – trifluralin, bensulide, DCPA, and napropamide are available for use. Broadleaf weed control will be limited and cultivation or hand hoeing may be necessary. Insect pests are similar to other cole crops and include caterpillars (imported cabbage worm, diamondback moth, cabbage looper, armyworms), aphids, thrips, and harlequin bug. Diseases include black rot, Alternaria leaf spot, and downy mildew.
The sprouts that are harvested are buds that grow to resemble miniature cabbage heads. They are produced in leaf axils along the main stem, which can grow up to 4 feet in height. To encourage sprout development, cut off the terminal bud of the plant (top the plant) when sprouts begin forming, which will be in September on Delmarva. Sprouts will take about 30 days from topping to harvest. Plants that are not topped will develop sprouts more slowly but will also produce over a longer season. Remove leaves on the lower part of the stem as the sprouts enlarge.
Brussels sprouts plants in the field with enlarging sprouts and lower leaves removed.
Sprouts for local sales can be harvested at a diameter of ¾ inch; whereas sprouts for wholesale markets should be allowed to get about 1½ inch in diameter before harvesting. Sprouts are cut or snapped off of the stem and are often directly harvested into pint or quart containers or bags. Potential harvest period for our region is the end of September through November or a heavy freeze. Sales into December are possible, especially with supplemental row covers. Brussels sprouts are very cold tolerant (hardy down to 20°F) and flavor will improve (they will be less bitter) in the colder part of the harvest season. Yields will be 2-3 lbs/plant.
An alternative method of harvest is to cut entire stems once the majority of sprouts have sized, remove the leaves, and sell as sprouts on the stalk. This is a popular method for roadside stands and other direct markets and requires much less labor.
Brussels sprouts can be room cooled, forced air cooled, hydrocooled, vacuum cooled, or top iced. They should be brought to a temperature of 32-34°F and kept at high humidity (90-95%) for storage or transportation and benefit from top icing. Brussels sprouts have a relatively long shelf of 3-5 weeks if properly stored.
Brussels sprouts for sale on the stalk