Broccoli
Most varieties of broccoli grow as annuals, producing a large head at the end of the season and that’s that. But perennial broccoli, also known as sprouting broccoli, produces many small, tender florets. Broccoli can be grown as a perennial even in areas where temperatures hit minus 20 degrees. The fact that it loves cool temperatures makes it an especially good fit for cool-weather gardeners.
VarietiEs
The most popular perennial variety is Broccoli Raab, which can be a little bitter. Also popular is Nine Star, which produces an abundance of white florets. Gailan, or Chinese broccoli, yields many small and tender florets with smooth stems that are delicious. Leaf broccoli varieties have leaves with a sweet kale-like flavor.
WHERE BROCCOLI THRIVES
Regional compatibility
Broccoli can grow all across the United States but it does best in cool areas where summer temperatures do not exceed 80 degrees. When heat-stressed, broccoli tends to bolt, or flower, which means it won't produce a head. You can slow the process of bolting in hot climates by cooling the soil with mulch as the summer heats up.
Optimal shade & sun
Plant broccoli in full sun. This vegetable thrives in about six hours of sunlight a day. In hotter climates, this perennial will benefit from afternoon shade.
RESILIENCE
ADAPTABILITY TO CLIMATE EXTREMES. Broccoli is adaptable to cold temperatures and mild frost. And dry conditions aren't a problem for broccoli if the soil is kept rich, well-nourished, and cooled with compost and mulch material. Prolonged heat, on the other hand, can be bad for broccoli because the stress can lead it to flower prematurely and turn the plant bitter. Broccoli is also sensitive to salty soils so it's not a great candidate for coastal plantings.
DROUGHT RESISTANCE. Dry conditions aren't a problem for broccoli if the soil is kept rich, well-nourished and cool with compost and mulch material. Prolonged heat, on the other hand, can be bad for broccoli.
PREP YOUR SOIL
Broccoli does best in well-drained, heavily composted sandy soil. It has a shallow root structure compared to other perennials so it can be grown in shallow soils.
PLANTING
PLANTING INDOORS. Plant two to three broccoli seeds in about a half-inch of soil in four-inch pots, either in the spring or the fall. Thin your plants to one seedling per pot after they've sprouted three leaves. No heat mat is needed for starting broccoli seeds. This hearty vegetable is frost-tolerant and can germinate in soil temperatures as low as 40 degrees. Your concern should be getting them in the ground before they become root bound. Broccoli plants left in a small pot for too long will bolt, or flower too early, as soon as they are transplanted. If you're planting a fall crop, make sure seedlings are kept cool and shaded prior to putting them in the garden in late summer. Excessive heat will produce spindly and unproductive plants. For that reason, you'll get the best results if you plant in the spring or fall, rather than in the summer.
PLANTING OUTDOORS. If you wish to plant directly in your garden sow three to four broccoli seeds per foot about a half-inch deep. Thin each planting to one plant per foot once the seeds have sprouted. If you started seeds indoors and have seedlings, plant them about 1.5 to 2 feet apart once the danger of a hard spring frost has passed. The farther apart you plant your broccoli the more likely its head will grow.
Growing
Broccoli grows fairly straight on sturdy stems. You'll know it's ready to harvest when it develops its head in the center of the plant. Plants can become top heavy in shallow soil. To stabilize your broccoli, tie it to bamboo stakes when its head starts to develop. Broccoli plants do not need to be pruned but remove the bottom leaves once they begin to wilt to prevent mildew. If you want your brocoli to sprout continuously take care to prevent any heads from flowering and producing seeds. Once plants have started seeding they'll stop producing shoots. Weeds tend to be a concern only when broccoli first sprouts. Since broccoli has a shallow root system, weed your site well before planting it so the weeding process doesn't uproot it. Mulching with shredded leaves or straw can help limit weed growth, particularly at the beginning of the growing season. After the heads grow it's generally harder for weeds to grow underneath broccoli because the leaf canopy is so large. Broccoli loves nutrient-rich soil so apply a layer of compost each spring.
WaterinG
Give your broccoli plenty of water but make sure you let the soil dry out between waterings so the roots don't rot. A lack of water can prevent broccoli from developing its signature head so try to give your plants roughly one- to-two inches of water each week.
Mulching
Mulching with shredded leaves or straw can help limit weed growth, particularly at the beginning of the growing season
CHALLENGES
PESTS. Cutworms, cabbage worms, and flea beetles are all broccoli pests. Placing a paper towel or toilet paper cardboard tube over the broccoli stalk while it's young and thin eliminates cutworms. You can also put a ring of diatomaceous earth (DE) around the stem of your brassicas to stop cutworms and slugs. DE is made from pulverized marine phytoplankton and is very sharp. When pest crawl over it, the shards cut their soft flesh or absorb into their joints, eventually killing them. The DE needs to be reapplied after heavy rains and should not be directly watered on. Flea beetles are much more difficult to control. They are fast moving and have a hard shell that protects them from many organic treatments. They do not like wet leaves so misting your plants can keep the number down. The best defense is to place yellow sticky traps every five feet around your plants. The beetles are attracted to the yellow tape and their small bodies are no match for the adhesive. Cabbage worms can be hand picked off or controlled using an insecticidal soap.
DISEASES. Club root fungus and various types of rot can attack broccoli. To prevent this from happening keep the soil well-drained. If your plant is hit by club root, increasing the soil pH by adding some lime can slow the infection. Ultimately the plant will have to be removed and you'll need to avoid planting broccoli in that location next season. Yellow patches on leaves, a symptom of downy mildew, are usually caused by moist weather. Keep leaves as dry as possible and don't crowd them so they benefit from good air circulation.
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