Broccoli (Brassica oleracea) has long been a favorite homegrown vegetable, dating back thousands of years to the Mediterranean region. It tops the list of nutrition-packed vegetables—it’s high in vitamins A and C, riboflavin, iron, folate, niacin, and calcium. Broccoli is praised for its high content of sulforaphane, a natural chemical that induces enzymes to detoxify cancer-causing agents. This tasty vegetable also contains indoles—nitrogen compounds that appear to protect our cells’ DNA from carcinogens. No wonder broccoli is considered the number one cancer-fighting vegetable.
The best news for home gardeners is that broccoli is not only healthy and delicious, but also easy to grow. With careful planning, you can get months of nonstop broccoli production.
Plant for seasonal harvests
For the best broccoli production, plant early, midseason, and late varieties. This way, you can scatter the harvest across the entire season.
Plant early varieties as early as possible in your region. Plant midseason varieties around the same time as early varieties. They require an extra week or so to mature, so they’ll extend production into early summer.
For late varieties, sow seeds directly in the garden in late June, July, or August (depending on your region and the variety’s days to maturity) for harvest after a light autumn frost.
Like all cole crops, broccoli needs a rich, loamy, well-drained soil chock-full of organic matter. The plants are heavy feeders and have a high demand for nitrogen, phosphorus, and potassium. About two or three weeks before planting seedlings, work generous amounts of compost and well-rotted manure into the broccoli bed. If your soil is acidic, use ground limestone to sweeten the soil to a pH of about 6.7 to 7.0.
The sweetest, most tender broccoli is harvested in cool weather. Broccoli produces best when the nights are 60°F to 70°F and daytime temperatures stay below 80°F. Hot weather can turn broccoli bitter and cause the plants to “bolt” into seed production, so plan ahead to make sure your plantings mature while the weather is still cool. To further beat the heat, plant broccoli in a bed that receives partial shade in the afternoon.
Sowing and growing
When buying broccoli plants from garden centers, you usually have no idea how old the seedlings are, what stress they’ve encountered, or what diseases they may be carrying. If you start your own plants from seed, on the other hand, you have better control of the variables and can choose from a wider selection.
Start your plants indoors five to seven weeks before the expected last frost date in your area. For example, if your region’s last expected frost is on May 15, you’ll need to start broccoli seeds in late March or early April. (Keep in mind that the “days to maturity” indicated on a broccoli seed packet refers to the time after you plant seedlings in the garden.)
The seeds germinate quickly. When the plants are two weeks old, move them to a cold frame to harden off, or harden them off gradually by placing them outdoors for increasing amounts of time each day. Transplant them two to three weeks before the last frost date. Small, month-old plants make the best transplants; older plants are usually stressed and often doomed to failure. If a hard frost is expected, protect your transplants with cloches, plastic cones, or other covers.
For late summer or fall crops, sow seeds directly in the garden. Your fall broccoli should mature around the first expected frost date in your area, so plant most varieties two to three months prior to that date. Studies have shown that direct-seeded broccoli produces higher yields than transplants.
Spacing is critical for broccoli. Its shallow root system needs room to spread to obtain enough water and nutrients, and it doesn’t compete well with other deep-rooted heavy feeders. Studies have shown that generous spacing between plants produces larger heads and increases yields significantly. If the plants are spaced too tightly, you’re likely to get “button” heads and few side shoots. Space your plants at least 18 inches apart; 24 inches is ideal for most varieties.
Mulch will keep weeds at bay and will help keep soil cool and moist. Spring crops, in particular, will appreciate several inches of clean straw, leaves, and compost when warmer weather arrives. You can also plant a “living mulch” of lettuce, spinach, and other leafy greens around the broccoli plants. These shallow-rooted plants shade the soil and make efficient use of valuable garden space.
Water moderately throughout the season. The critical time for watering is early in the season, to prevent “buttoning” (minuscule heads), and during head maturation. Do not water from overhead with a hose or sprinkler when the heads are maturing, because water pooling on the heads can lead to disease problems. Instead, use soaker hoses or a drip-irrigation system, or water by hand at the base of the plant.
Broccoli heads are actually immature flower clusters and must be harvested at their prime. Check the broccoli every morning as it nears maturity. Gently rub the heads with your thumb—if the buds are tight and firm, let the plants grow another day. If the buds feel loose, it’s time to harvest. If the buds begin to show yellow and are about to blossom, you’ve waited too long.
For varieties that produce side shoots, cut the central head about five inches down the stalk, removing some of the developing nodes. This helps the plants produce large side shoots at the lower nodes. Cut the stalk at an angle to prevent rainwater from pooling in the cut stem.
Controlling pests and diseases
Here are the most common broccoli pests and what to do about them:
Cutworms: A plastic cup with its bottom removed makes a simple cutworm collar. Push the cup, wide end down, about 1 inch into the soil around each plant. Cutworms won’t climb over or dig under the collar. When the broccoli stem is large enough, remove the cup.
Cabbage loopers, root maggots, and cabbageworms: To keep moths from laying eggs on your plants, grow plants under a floating row cover. Row covers also protect plants from the flies that produce root maggots. Cover plants immediately after planting and leave the cover on throughout the season. Even when the weather gets warm, the lightweight covers don’t overheat the plants.
As a second precaution against ravenous caterpillars, use Bacillus thuringiensis, better known as Bt and sold under the trade names Bactur, Dipel, and Thuricide. A natural pesticide, Bt kills only butterfly and moth larvae and is nontoxic to humans and animals. Spray broccoli weekly as soon as you see tiny cabbageworms on the undersides of the leaves.
Disease problems: Plant disease-resistant varieties, and make sure at least three years pass before you plant a cole crop in the same garden space (especially if clubroot, a soil-borne fungus, is a problem in your garden).
14 favorite broccoli varieties
‘Early Dividend’ (43 days) One of the largest broccoli varieties. Produces a central head up to 12 inches across as well as side shoots 3 to 4 inches across.
‘Green Goliath’ (53 days) Bred for early and extended harvest. Large blue-green heads have many side shoots.
‘Packman’ (50 days) Widely adapted to various garden conditions, and can be grown early, midseason, or late; extra-early spring plantings may “button,” however.
‘Small Miracle’ (54 days) Small, compact plants with large 7-inch heads; tolerates closer spacing than other varieties.
‘Southern Comet’ (55 days) All America Winner with large central head and rapid growth of side shoots.
‘Belstar’ (60 days) Holds its mature central head for over a week; some side shoots.
‘Coronado Crown’ (58 days) Highly heat-tolerant. Produces an 8-inch head and plenty of side shoots.
‘Gypsy’ (58 days) Produces uniform, medium-sized heads on large plants; heads hold well in warm weather.
‘Nutribud’ (58 days) Open-pollinated variety with large amounts of glutamine (an important healing nutrient).
‘Premium Crop’ (62 days) Produces large heads with superior flavor, but few side shoots—basically a one-head crop.
‘Diplomat’ (68 days) Produces uniform, medium to large heads. Performs especially well in the Northwest and Northeast.
‘Marathon’ (68 days) Highly tolerant to cold; a popular variety in California.
‘Minaret’ (95 days) An open-pollinated Romanesco type (Italian broccoli with a conical head and distinct taste) that produces light-green clusters of spiral buds.
‘Waltham 29’ (80 days) The traditional late broccoli, popular since the late 1950s (when it was introduced); open-pollinated; compact plant with many side shoots.
Weldon Burge is a garden writer in Newark, Delaware.