Broccoli is the flowerhead of a member of the cabbage family.
As a brassica, broccoli is cousin to kale, collard greens, rutabagas, watercress, Brussels sprouts, Romanesco broccoli, and cauliflower. Native to the northern Mediterranean region, modern broccoli is the result of centuries of careful breeding that started in the 6th century BC.
Broccoli (Brassica oleracea) has been dreaded by children for decades. This is often due to overcooking and freezing.
“Eat your trees!” Mothers have cajoled for generations. The truth is, broccoli contains bitter compounds and some people are more sensitive to it than others. There is no sense fighting over genetics. What you can do, for those family members on the broccoli fence, is to offer fresh, tender broccoli shoots, steam broccoli lightly, and there is always the cheddar cheese trick. [Cheese makes everything taste better, right?]
How to grow broccoli
Broccoli is a slow grower. It can 3 months or more, from seed to harvest. In the Bay Area, broccoli can be started from seed twice a year. For a summer harvest, plant in February, March, and April. For a late winter, early spring harvest, you can plant broccoli in August and September. Some years, you can plant as late as October. Broccoli loves cold temperatures and will bolt in hot weather. Also, heat stress can cause bitterness. Broccoli prefers full sun, but your spring crop can be grown in partial shade, to avoid heat stress, but it will benefit from strong morning sun. Broccoli prefers slightly acidic soil, so your plants will thank you if you perform a little acidification before planting. Seeds should be planted 1/2 inch deep. It is best to start plants in small containers and then transplanting when they have three or four true leaves. Plants can be placed in the ground slightly deeper than the soil level when transplanting. These plants get large, so be sure to provide plenty of growing room. They usually need a 2-foot square space, or more, per plant. Broccoli roots are shallow, so avoid digging around plants. To reduce weeds, mulch heavily. Broccoli needs a lot of water, so irrigate consistently, without getting the heads wet.
There are three basic types of broccoli. The common grocery store variety is Calabrese broccoli. Sprouting broccoli has many small heads on thin stalks. Purple broccoli looks more like its cousin, cauliflower, with an occasional purple tint to flower buds. Not exactly a true broccoli, broccolini is a cross between standard broccoli and Chinese kale, or gai lan.
According to Santa Clara County Master Gardeners, the following varieties of broccoli perform best in our area:
Broccoli pests and diseases
Downy mildews, bacterial leafspot, clubroot, damping off, powdery mildew, phytophthora root rot, and ringspot are common diseases of broccoli plants. Most of these are caused by poor irrigation practices. As for pests, well, we’re looking at all the usual suspects: aphids, whiteflies, bagrada bugs, crickets, earwigs, armyworms, leafminers, slugs and snails, thrips, and wireworms. You will also have to watch for cabbage loopers, cabbage maggots, cabbage aphids, and imported cabbageworms. Bacillus thuringiensis (Bt) sprays can help protect against some of theses. Imported cabbageworms will probably cause the most damage. The larva of an erratically flying white moth match the color of leaves and often are not seen until significant damage occurs. Row covers can protect against this particular pest. Since the moths fly, they can always come back to lay more eggs. Personally, I have trained my dogs to chase them away. Once in a while, they actually catch one! Braconid wasps will also help fight off some of these pests, so avoid using broad spectrum pesticides. Environmental conditions can also interfere with a successful broccoli crop. Early stress can cause plants to flower too soon, creating tiny heads. This is called buttoning. Too much heat can cause brown bud - it’s not pretty. Heat (and insufficient boron) can also cause hollow stem. Too much nitrogen in the soil can cause broccoli plants to produce plants of (edible) leaves, but no flowers. [Have I mentioned getting your soil tested?]
As flower heads develop, use a sharp knife to cut the stem an inch or two below the head. Delicious fresh, broccoli can be stored in the refrigerator for a short time, or frozen for longer storage. Broccoli is especially susceptible to the ripening effects of ethylene gas, so keep your broccoli away from foods such as apples and bananas.
After you have harvested your broccoli, cut plants off at ground level and chop up the remainder, spreading it out over any areas in the garden prone to Verticillium wilt. There are chemicals in broccoli that harm the fungi.
Young broccoli sprouts, cauliflower, and mustard greens all contain a chemical called glucoraphanin, which is converted into substances that fight infection, arthritis, and cancer. They can also ‘retune’ metabolism. So, eat your trees! And start planting!
Romanesco broccoli (Jon Sullivan)
Sicilian purple broccoli (Phytism)
Imported cabbageworms are an insidious garden pest.
Cannageworms start out as tiny yellow or white, rocket-shaped eggs that are laid singly on the undersides of leaves. Then, slightly fuzzy green caterpillars emerge and start feeding, and feed they do!
According to the UC IMP (Integrated Pest Management) page: biological controls include natural enemies such as the pupal parasite Pteromalus puparum; the larval parasites Apanteles glomeratus, Microplitis plutella, and several tachinid flies; and egg parasites in the Trichogramma genus. Biological control and sprays of Bacillus thuringiensis (Bt) and the Entrust formulation of spinosad are organically acceptable management tools.
In addition to regularly monitoring plants for the presence of cabbageworms, I have trained my dog to chase cabbage butterflies out of my yard.
I hope this information inspires you to grow more of your own food. You can ask your garden questions on my Home page.