Brussel Sprouts
(Brassica oleracea, Gemmifera group)

Type: Cool season annual

Hardiness Zones: 4-7, and Zone 8 as a winter vegetable. A cool-season crop, generally unsuited to warmer climates

Varieties: Both open-pollinated and hybrid cultivars are available. Hybrids tend to have stronger root systems making them less prone to leaning (a mature plant can reach 2.5 to 3 feet (1 m) tall) and their sprouts mature more evenly. There are two basic types of Brussel Sprouts: 1) the dwarf (e.g. “Jade Cross”), which matures early and is winter hardy but more difficult to harvest; and 2) the taller (e.g. “Long Island Improved”), which is less hardy but easier to harvest.

Size & Spacing: 24-48” height; 24” breadth; 18-36” root depth. Plant 18 to 24 inches apart; 2 to 3 feet between rows. At least 12” deep and 12” in diameter per plant. Only one plant per pot.

Support Structures: Brussel sprouts have shallow roots, so as they become top heavy, you may need to stake them, particularly if exposed to strong winds.

Temperature: 50-80° F for germination; 60-65° F for growth.

Site: Full sun. Rich, well-drained, fertile soil with good calcium levels; pH 5.5 to 6.8. To avoid disease and pest problems, allow three years between plantings of the cabbage-family (cabbage, kale, cauliflower, and broccoli) in the same area. Sprouts grow really well in soil that previously grew legumes like peas and beans. Brussels sprouts grow well in either flat rows or raised beds, and it is very important that the soil is rich and well-prepared because sprouts have such a long growing season.

Companion Planting: Plant near candytuft, clover (white), cover grass, french beans, shepherd’s purse, weedy ground cover, wormseed mustard, celery, chamomile, dill, garlic, mind, onion family, radish, rosemary, sage, savory, tansy, thyme, wormwood. Also does well with artichoke, beet, peas, potato, spinach. Keep away from Kohlrabi, all pole beans, strawberry, tomato.

Diseases, Pests & Common Problems: To avoid soilborne fungal and viral diseases, rotate with non cabbage-family (cabbage, kale, cauliflower, and broccoli) crops. Use row covers to help deter flea beetles, cabbageworms, and root maggots, and use insecticidal soap if cabbageworms or aphids are a problem.

Planting & Growing: Brussels sprouts require a long growing season and are best when matured in cool weather. For most areas, because this is a cool-loving crop, it's best to plant five-and-a-half months before the first expected fall frost. Where growing seasons are long, you can direct sow fall crops in July; in mild-winter areas, time your crop for winter-to-spring harvest. Gardeners who live in short-season climates can set out transplants in early spring. Soil temperatures must be over 50° F (C) for good germination. Keep weeded or use mulch to hinder weed development. Pinch off top leaves to encourage side growth. Give Brussels sprouts steady moisture, especially when the air temperatures rise over 80° F (C) because hot, dry spells will stunt sprout formation. Mulching will help keep soil temperatures cool and moisture levels steady, while helping keep weeds under control. As sprouts form in the leaf axils (see picture above), snap off the leaves beneath them. This will help channel the plant's energy into forming the sprouts. For the best sprout growth, when a node begins to bulge, remove the leaf below it. 3-4 weeks before harvesting, when the sprouts are 1/2 to 3/4 inch (1.5 to 2 cm) in diameter, you can do one of two things: 1. If you want the sprouts to ripen all at once, pinch off the growing point (the cluster of leaves at the very tops of the main stem). This will help the plant concentrate on sprout formation. 2. You can allow the plant to grow naturally and your sprouts will mature over a longer period of time, extending your harvest.

Watering & Fertilizing: Need steady, even moisture. Hot, dry spells will stunt sprout formation. If using transplants, lightly feed at planting time. Lightly broadcast some 10-10-10 over the area, till in, and then plant transplants or sow seeds. When the plants start to form sprouts that are marble sized, side-dress with 1 tablespoon (15 ml) per plant of 5-10-10, or one large handful of good compost which generally equals the same. Sprinkle around the base of the plant, but not up against the stem, and water in.

Days to Maturity: 90 to 120 days

Propagating: All members of Brassica oleracea will cross with each other. Isolation distances of ½ mile are necessary for purity, unless alternate day caging is used. Barriers such as tree lines, woods or buildings in between varieties can allow for shorter distances. Transplant in early spring and allow plants to flower after forming a compact head. Seed can take a very long time to mature and may require some season extension. Gather seed stalks when seed pods are dry being careful to prevent losses due to shattering. Use a 1/8" screen to help with cleaning.

Harvesting: Harvest sprouts, starting from the bottom of the stem, when they reach 1 to 2 inches (2.5 to 5 cm) in diameter. If you haven't already done so, break off the leaf below the sprout and then snap off the sprout. Sprouts higher up along the stem will continue to grow. Entire stalks can be harvested, it's up to you. In cold-weather areas, complete your harvest before the ground freezes. Some say never to harvest unless you’ve had at least two frosts, because frost improves flavor. It has also been reported that sprouts can be harvested throughout the summer and still be tender if continuously picked when they reach the size of marbles.

Storage: Brussels sprouts are best eaten fresh, but you can store them up to three weeks in a plastic bag in the refrigerator. They can also be blanched and frozen.

Resources:

Recipes:

Customizing Your Gardening Calendar:

First Seed-Starting Date: Count back 45-80 days from your average last freeze date and start seeds indoors. Allow 3-10 days for germination and 28-49 days for growth before transplanting outdoors. Transplant 14-21 days before your average last freeze date.

Last Seed-Starting Date: Count back 118-145 days from your average first freeze date and start seeds indoors or sow direct in the garden. Allow 3-10 days for germination and 21 days for growth before transplanting outdoors. Then allow 80-100 days for maturity and 14 days allowance for short, cool days.

Sample Gardening Journals for Zone 4 (LFD May 20; FFD Sept 20):

2012

4/6 started 24 Long Island Improved Brussel Sprouts indoors in homemade potting soil; APS24, 1 per cell
5/13 Transplanted 6/24 Brussel Sprout (very low germination rate)