Growing Broccoli Tips and Considerations
By Kris Wetherbee
Romanesco and purple cauliflowers are members of the same family as broccoli.
When it comes to growing broccoli, fantastic flavor is always the ultimate reward. Here are some tips to help you grow great-tasting broccoli that is heads and shoulders above the rest.
During market days, our customers were amazed at the size and flavor of our broccoli. I attributed some of the credit to the use of rabbit manure and choosing the right variety, but a lot of the credit goes to the vegetable itself. Its culinary versatility, million-dollar taste, and ease of cultivation make broccoli one of the most desirable vegetables to grow. And when grown to maturity in the cool weather of spring or fall, the result is a sweeter-tasting head with truly gourmet flavor. To produce the biggest and tastiest heads, keep these tips in mind.
Be selective with broccoli varieties
Different broccoli varieties are designed for different growing seasons. Some perform best when planted in early spring, while others excel when planted later in summer for a fall crop. For example, Packman is an early-maturing variety best suited for a fall crop; it’s prone to buttoning (producing smaller than normal heads) if planted in early spring.
Some great spring broccoli varieties are Blue Wind, Express, Belstar and Fiesta. Varieties that tolerate summer’s heat include Arcadia, Green Magic and Gypsy. Prime picks for a fall harvest include Premium Crop, Marathon, and the ever-versatile Arcadia and Belstar — and Packman.
Also consider when and how a variety develops its head. There are two types of broccoli: heading and sprouting. Some heading types form usable side shoots once the central head is cut. Sprouting types form lots of small florets within the leaf axils. Some heading types have excellent side shoot production while others mature their heads all at the same time — perfect for freezing.
Other varieties, like romanesco, grow an enormously large plant that takes up a lot of space. If you have limited space, or plant in containers, there are a few varieties that use less than 1 square foot, such as Small Miracle.
Growing broccoli: focus on speed
Broccoli belongs to the Brassica genus and is closely related to other cole crops such as cabbage, cauliflower and brussels sprouts. The real secret to growing a prime head of any cole crop is to grow it fast.
One way to get your broccoli off to a fast start is to know when to use seeds and when to use transplants. Transplants are often best for early plantings, as seeds have a tough time germinating in cold soil. You can grow your own transplants by sowing seeds indoors five to eight weeks before your last spring frost. Set 4- to 6-week-old hardened-off starts into the ground about four weeks before your last spring frost, or up to seven weeks if properly cloched. Young seedlings can withstand a light frost, but cover them if a heavy frost is expected.
Seeds sown directly into the ground often produce more vigorous plants with increased resistance to disease, insects and stress. Direct-seeding works well for fall-harvested crops. Sow seeds 1/4 to 1/2 inch deep, with two to three seeds per hole. For raised-bed or wide-row gardening, space seeds 12 to 15 inches apart for earlier sowings, and 15 to 18 inches apart for fall varieties. Large romanesco types like Minaret should be planted 18 to 24 inches apart. Cover the seeds with loose soil or sifted compost and be sure to keep the seed bed moist.
Another way to get broccoli growing fast is to provide the right conditions of sun, soil and water.
Broccoli grows best in a sunny spot (at least five hours of sunlight daily) in fertile and moist but well-drained soil rich in organic matter, such as aged manure, compost or leaf mold. A soil pH range of 6.0 to 6.8, with a soil temperature range of 55 to 75 degrees, is ideal.
The soil also should have a good moisture-holding capacity and receive 1 to 2 inches of water per week. Mulching helps maintain an even soil moisture and moderate soil temperature.
To produce big and tasty broccoli heads, you will need to keep them well fed. Before planting, work a 2- to 4-inch layer of compost or a thin layer of well-aged manure into the soil. Another option is to fertilize only the planting hole rather than the bed. Work in about a half shovelful of aged manure or compost, or mix in 1/4 cup (per plant) of complete nitrogen-rich organic fertilizer.
The nitrogen boost is crucial in getting early spring varieties off to a fast start when the soil is cool. If your soil fertility is poor, water plants with fish emulsion or a manure or compost tea about two weeks after transplants go into the ground. Depending on your soil fertility, you also may want to lightly side-dress with a nitrogen-rich fertilizer or other organic source, such as fish meal, when the central head is 1 inch across. An additional side-dressing may be needed once the central head has been cut to promote an ample supply of side shoots.
Keep plants calm
Sometimes stressing a plant just a bit can result in better flavor, such as withholding water from tomato plants once their fruit changes color. Not so with broccoli.
Avoid using inferior transplants. Select the best 4- to 6-week-old starts for setting out. Older starts are usually rootbound and therefore stressed, making them more susceptible to buttoning. Another stressor is lack of adequate moisture, which can result in premature, poor-quality heads. Chill also is a stressor. Broccoli grows best in cool temperatures and can tolerate frosts down to 20 degrees F, though extended temperatures below 35 degrees can turn buds purple and sometimes soften heads. Floating row covers can provide additional protection, extending the season by three to four weeks.
Another stress factor is destructive pest insects. Cabbage loppers and cabbage worms present the biggest problem. They are best controlled by introducing parasitic trichogramma wasps, or applying Bacillus thuringiensis — a naturally occurring, nontoxic bacteria also referred to as Bt. Aphids can easily be controlled with a hard spray of water or spraying with insecticidal soap. Better yet, plant nectar flowers to encourage lacewings. Also known as “aphid lions,” their ravenous larvae are avid aphid eaters — one lacewing larva can consume up to 60 aphids in an hour.
Don’t miss the signs as to when to harvest the heads. For best flavor, harvest the central head when the unopened flower buds are just starting to swell, but before they open and reveal the yellow petals. (Broccoli can still be eaten when buds begin to flower, but the taste will be a bit stronger.) Harvest heads in the cool of the morning. Cut the central stalk at a 45-degree angle, 5 to 8 inches below the head to encourage side shoot production and increase yield. Harvesting side shoots regularly will encourage continued production.
The last key to keeping the flavor intact is to not overcook the florets. Cook them only until they are tender-crisp and bright in color. Broccoli is great steamed or tossed into stir-fries.
Broccoli is more than a once-a-year, one-shot affair. By planting early, midseason and fall varieties, you can extend your harvest over most of the year.
A food writer and recipe developer, Kris Wetherbee grows broccoli and more in her Oregon garden, preserving all the bounty nature provides.
Broccoli seed sources
Johnny’s Selected Seeds
955 Benton Ave.
Winslow, ME 04901
Pinetree Garden Seeds
P.O. Box 300
New Gloucester, ME 04260
Territorial Seed Co.
P.O. Box 158
Cottage Grove, OR 97424