For many gardeners, growing a good crop of Brussels sprouts doesn't come easy. My first crops grew to lopsided nubs, and indeed several seasons passed before I began harvesting crisp, sweet sprouts. The truth be told, Brussels sprouts have exacting cultural needs unlike those of any other vegetable. But when those needs are met, you get a two-month (or longer) supply of this gourmet vegetable, which are especially welcome in early winter.
I've sorted the special needs of Brussels sprouts into a seasonal checklist of details that should not be skipped over. Brussels sprouts plants are as tough as any cabbage, but special techniques are needed to make the most of their stalwart nature.
Plant at the right time
Gardeners in the UK set out Brussels sprouts seedlings in April and grow them just like long-season cabbage. This will work in the cool maritime climates of the US, but in most areas it is best to delay planting until early summer. Use multiple sources – your GrowVeg Garden Planner (using the split season option in warm climates), state extension service publications, and the knowledge of local gardeners to find your perfect planting window, which may be only one week in early to midsummer. In my garden, for example, I have learned that I must start seeds indoors between June 3-10. Keep records and make notes until you find the right planting dates for you.
Choose a site with heavy clay soil
Brussels sprouts grow into stiff, topheavy plants with skinny bases that are easily damaged by rocking in the wind. Plants that fall over will continue to grow, but will not produce nearly as well as plants that stay upright. Light, sandy soils cannot adequately anchor Brussels sprouts plants, even when they are propped up with stakes and have soil mounded up around the base. Dense clay loam with a few rocks is essential. A slightly acidic to near neutral pH is ideal. In the UK where the soil-borne disease called clubroot is common, some gardeners have found that lightly dusting the planting hole with lime reduces problems and increases yields.
Provide slow-release fertilizer
Brussels sprouts plants are heavy feeders that must enjoy uninterrupted growth. If you have rotted poultry manure, you will find no better use for it than as a pre-plant fertilizer for Brussels sprouts. Packaged organic fertilizers are fine, too. Thoroughly mix your fertilizer of choice into the planting site several days before you plan to set out your plants.
Use row covers to prevent insect pests
Numerous insects from cabbage worms to grasshoppers will quickly devour unprotected Brussels sprouts seedlings. Lightweight garden fleece or row covers made from tulle will protect plants as they soak up summer's heat – an essential factor in the making of a good crop. If you live where summers are very hot, do not wait until the weather cools down in the fall to set out plants. This I learned the hard way: Brussels sprouts must have a good shot of summer sun to grow into big, robust plants.
Keep roots cool, moist and well fed
I favor a grass clipping mulch for Brussels sprouts, which keeps the soil cool while contributing a little nitrogen. Brussels sprouts should never be allowed to dry out completely, and I like to feed them with a high nitrogen liquid fertilizer every two to three weeks, just in case they need it. Ideally, you want Brussels sprouts to grow into stocky, knee high plants before they elongate and start popping out sprouts. Once production begins, each plant produces about five sprouts weekly. By the time the harvest finishes (December at my house), each plant should have produced 30 or more sprouts on a 4-foot long stalk.
Things seldom go perfectly in the garden, so I always plant two or three more plants than I need. Plants that fall over get pulled out, because in addition to not producing well, I have found that they become aphid magnets. Healthy upright plants have fewer problems with this chronic pest of fall, which can be managed to some extent with weekly harvesting followed by spritzing with insecticidal soap. Survivors can be rinsed off with cool water when the sprouts are cleaned before cooking.
Harvested Brussels sprouts will keep in the fridge for a couple of months, but of course they will never last that long. I favor braising sprouts cut into halves, quarters or thin slices in hot butter or olive oil, which brings out the beauty and flavor of this challenging yet supremely rewarding vegetable.
By Barbara Pleasant