Broccoli is a stout, thick-stemmed plant in the Brassicaceae family, which also includes cabbage, kale, Brussels sprouts, and several Asian greens, like bok choy. The part we eat is actually the buds of the broccoli flower. If left unharvested, the broccoli head will open into small greenish-yellow flowers. Although most broccoli is green, there are also some delicious and beautiful purple varieties.
Broccoli is so rewarding to grow because it gets your garden started early and continues to send up side shoots for weeks, after you harvest the main head, giving you a long harvest season. Broccoli varieties that are prolific at sending up these side shoots are often listed as sprouting broccoli. If you’re a broccoli lover, having even a few plants in the garden will give you a steady supply.
Brassica oleracea var. italica
Broccoli, Sprouting Broccoli, Calabreseitalica
Broccoli is a biennial, but it can go to seed the first year if planted in early spring. Because it is not a perennial plant, it has no USDA Hardiness Zone.
As with most vegetables, broccoli grows best in a spot with full sun. However, in very hot climates, partial shade should help prevent bolting.
Most broccoli varieties will grow about 2 1/2 feet/76 centimeters (h) x 8 to 12 inches/20 to 30 centimeters (w). Plant size varies greatly with growing conditions and variety of broccoli.
Days to Harvest
Days to maturity will depend on the variety you are growing, but there are broccoli varieties that can begin being harvested about 48 days from transplant.
How to Harvest Broccoli
Don't wait until your broccoli produces a large head as you see in the grocery store. There are some large head broccoli varieties, but most are ready to start harvesting once they’ve reached the size of a large fist. If you wait too long to harvest, the buds will open. You can still eat the stalks at this point, but they’re a bit tougher and the cooked flowers turn from yellow to beige.
Cut the head with about 4 inches of stalk attached. New flower heads will soon form in the leaf axils and all around the lower stalk. These will be much smaller than the initial head, but still delicious. Keep harvesting and they will keep producing.
Suggested Varieties to Grow
- 'Blue wind' f1 (49 days): Improved 'Packman' type. Grows well in most climates.
- 'Calabrese' and 'de cicco' (60 days): Popular heirlooms. They start producing early and follow with lots of side shoots.
- Early purple sprouting broccoli (80 to 115 days): Sweeter than green broccoli, but it takes forever. Usually grown as a biennial and harvested the following spring.
- 'Romanesco' (75 days): Heads are spirals of lime green and the texture and flavor are great.
- Broccoli raab (Brassica campestris): A close relative, aka di rapa, rappone or turnip broccoli, never develops a large flower head. It's grown for the leaves.
- Soil: Broccoli prefers a neutral soil pH, right around 7.0. A rich soil, with lots of organic matter, will keep it growing strong throughout the season.
- When to plant: In colder climates, you’ll get a head start by starting seeds indoors 6 to 7 weeks before your last frost date. In about 4 to 5 weeks, the broccoli plants should have reached about 5 inches tall and they can be put outdoors to begin to harden off. Broccoli can handle a slight frost, once it’s hardened. Follow the same procedure for purchased broccoli seedlings. In warmer climates, you can direct seed broccoli in very early spring. In hot climates, you can get a second seeding done in late spring/early summer and possibly a late summer planting (July/August) for a fall crop. In areas with mild winters, broccoli will over-winter and be ready for harvest in the spring. Cool climate gardeners can direct seed, too, but you’ll need to wait until about 1 month before your last expected frost date.
- Transplanting: Broccoli can be planted an inch or two deeper than it was in its container. Water it well and protect it with a row cover or some other covering, if a hard freeze is expected. Cutworms can attack young broccoli plants, so wrapping a collar around them at transplant time is a good precaution.
- Spacing: Give each broccoli plant about 18 inches of room in each direction.
Broccoli doesn’t require a lot of attention until it’s time to harvest. Keep it well watered and it will grow.
Broccoli plants shouldn’t need supplemental feeding if your soil is rich. If they look like they need a boost or you want to hasten maturity, hit them with some nitrogen. Fish emulsion is good for this.
Pests and Problems
Broccoli is susceptible to the same pests as cabbage. The most common pests are cabbage looper, imported cabbageworm, cabbage root maggot, and aphids. These pests are more troublesome in the early part of the season.
Diseases include blackleg, black rot, and clubroot. Disease control is best obtained by rotating the crop each year. Clubroot is diminished when you raise the soil pH to about 7.0.