Cabbage is a cool-season vegetable suited to both spring and fall. It belongs to the cole crop family (Brassica oleracea), which includes broccoli, Brussels sprouts, cauliflower, collards, kale, and kohlrabi. The trick to growing cabbage is steady, uninterrupted growth. That means rich soil, plenty of water, and good fertilization.
Soil, Planting, and Care
Set out new spring plants early enough so that they can mature before the heat of summer, about 4 weeks before the last frost. For the best chance at success, be sure to start with strong, vigorous young Bonnie Plants®, which are already well on their way to maturity, giving you a jump-start on your garden . New plants just out of a greenhouse need to be protected from freezing weather. In the spring, consider planting through black plastic to help warm the soil. Plant fall cabbage 6 to 8 weeks before the first frost. Growing plants that have been exposed to cool weather become “hardened” and are tolerant of frost. Cabbage that matures in cool weather is deliciously sweet. Like most vegetables, cabbage needs at least 6 hours of full sun each day; more is better. It also needs fertile, well-drained, moist soil with plenty of rich organic matter. The soil pH should be between 6.5 and 6.8 for optimum growth and to discourage clubroot disease.
To be sure about your soil pH, get the soil tested. You can buy a kit or have a soil test done through your regional Cooperative Extension office. Apply fertilizer and lime if needed, using the results of the soil test as a guide.
In the absence of a soil test, add nitrogen-rich amendments such as blood meal, cottonseed meal, or composted manure to the soil, or amend the soil with Miracle-Gro® Performance Organics™ All Purpose In-Ground Soil to add valuable nutrition and improve texture. Plants grow best with a combination of good soil and just the right plant food, so work a top-quality continuous-release plant food such as Miracle-Gro® Performance Organics™ All Purpose Plant Nutrition Granules into the soil before planting. (As with any product, be sure to follow label directions.) Another option is to skip the in-ground garden in favor of growing your cabbages in containers filled with premium potting mix, such as aged compost-enriched Miracle-Gro® Performance Organics™ All Purpose Container Mix. That’s really the simplest way to know your plant roots have precisely the environment they need to grow.
Cabbage is easy to transplant. Set plants so that 1-2″ of the main stem is buried. Space according to directions on the Bonnie label. Generally, this is 12 to 24 inches apart in a row, depending upon the variety and the size of head it makes. For maximum size, be generous with the spacing. Our O.S. Cross Cabbage (known informally as Bonnie’s “Mega Cabbage”) for example, needs all the room you can give it!
Cabbage demands even moisture to produce good heads. Mulch with compost, finely ground leaves, or finely ground bark to keep the soil cool and moist and to keep down weeds. Water regularly, applying 1 to 1.5 inches of water per week if it doesn’t rain. You
can measure the amount of water with a rain gauge left in the garden.
Fertilize plants again with a liquid fertilizer such as fish emulsion or 20-20-20 after they begin to develop new leaves and when they start forming heads.
The best way to avoid problems is to keep your cabbage healthy and keep your garden clean. The main insect pests include cabbage loopers, slugs, imported cabbageworms, cabbage root maggots, aphids, and flea beetles. Disease problems include black leg, black rot, clubroot, and yellows. To prevent diseases from building up in the soil, avoid planting cabbage or other cole crops in the same spot each year. Rotate with a non-cole crop for 2 years before returning to the same spot.
Harvest and Storage
Cabbage is ready to harvest when the head forms, right? No, sometimes they look ready, but they aren’t. You can test the head’s solidity by squeezing it. A head that looks solid and ready may still be flimsy and loose leafed on the inside. When it feels firm, cut the head from the base of the plant. Some varieties hold well in the garden for weeks, while others need to be cut soon after the heads are firm. Our descriptions of Bonnie cabbage varieties indicate which ones hold best. If a head cracks, cut it right away. If you want to experiment, you can leave the harvested plant in the garden. If the weather is still cooperative, they develop loose little heads below the cut that are fun to serve as mini cabbages. Heads keep for several weeks in the fridge.
Why do butterflies fly around my cabbage plants?
Those butterflies (white or brown) are probably the moths of cabbage worms. They lay eggs on the plants. The eggs hatch into the worms that cause considerable damage unless controlled. Most control strategies are aimed at the developing larvae rather than the mature moths themselves.
Why are there holes in my cabbage leaves?
Your plant is probably being chewed by cabbage loopers or cabbageworms. Treat the cabbages with a product containing Bacillus thuringiensis (Bt) such as Dipel¨, a biological-type insecticide. This must be eaten by the worm and is activated in the worm’s alkaline gut. The worm then dies slowly from terminal constipation. This takes two to three days, which means the worms are not killed immediately.
What causes large, lumpy swellings of my cabbage roots?
Swellings and distorted roots on stunted, wilted plants are symptoms of clubroot, a disease caused by a fungus that remains in the soil for years once it becomes established. It is spread by moving infested soil and by infected transplants. Other cole crops (like broccoli and cauliflower) are susceptible. Destroy infected plants (including the roots) and for at least four years avoid planting any member of the cabbage family there, including radishes, turnips, and ornamental relatives of cabbage. To discourage the disease, add lime to raise the soil pH to 6.8.
What can I do to prevent my cabbage heads from splitting?
Splitting is caused by the pressure of excess water taken up after the heads are solid, or water being taken up quickly after dry weather. Cutting the roots (spading on two sides of the plant) or breaking the roots (lifting and twisting the head to one side) may reduce splitting or bursting, but it also damages the plant and requires that you harvest soon.
What causes cabbage to develop seed stalks rather than solid heads?
All cabbage will either head up or go to seed at some point in time. Cabbage plants “bolt” (form premature seed stalks) when exposed to low temperatures (35 to 45 degrees F) for extended periods if plants are set out too early or if an unseasonable blast of cold assaults the garden. After the plants have stems as large as a pencil, they are vulnerable to this “cold conditioning,” which initiates the flowering.