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.
The growth rate of broccoli ranges from moderate to slow. Depending on the variety, the days to maturity range from about 48 days to 115 days. It is typically planted in early spring for a summer harvest, but in some areas a second, late-summer planting can yield a fall harvest. As a biennial plant, broccoli can overwinter in mild climates and provide a spring harvest.
|Botanical Name||Brassica oleracea var. italica|
|Common Name||Broccoli, Sprouting Broccoli, Calabrese|
|Plant Type||Biennial (typically grown as an annual)|
|Mature Size||18 to 30 inches tall, 12 to 24 inches wide|
|Sun Exposure||Full sun|
|Soil Type||Moist, rich, well-drained loam|
|Soil pH||Neutral (7.0)|
|Flower Color||Green to yellow|
|Hardiness Zones||2 to 11|
|Native Area||Mediterranean, Asia|
How to Plant Broccoli
Plant broccoli seedlings 1 to 2 inches deeper than they are in their containers. Give each plant about 18 inches of room in each direction. Water them well and protect them 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.
As with most vegetables, broccoli grows best in a spot with full sun. In very hot climates, partial shade may be necessary to prevent bolting.
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.
Keep broccoli well-watered, especially during dry periods. Typically, the plants need 1 to 1 1/2 inches of water per week.
Temperature and Humidity
Broccoli plants do best in cool spring and fall temperatures between 65 and 70 degrees Fahrenheit. They begin to suffer when the temperature nears 80 degrees Fahrenheit.
Broccoli plants shouldn’t need supplemental feeding if the 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.
- 'Blue wind' f1: Improved 'Packman' type; grows well in most climates; matures in 49 days
- 'Calabrese' and 'de cicco': Popular heirlooms; begin producing early and follow with lots of side shoots; mature in 60 days
- Early purple sprouting broccoli: Sweeter than green broccoli, but much slower-growing; usually grown as a biennial and harvested the following spring; matures in 80 to 115 days
- 'Romanesco': Famous for its lime-green heads with beautiful spiraling pattern; good texture and flavor; matures in 75 days
- Broccoli raab (Brassica campestris): A different species but a close relative to common garden broccoli; also called broccoli di rapa, rappone, or turnip broccoli; never develops a large flower head, and is grown for its leaves; matures in 25 to 35 days
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.
How to Grow Broccoli From Seed
In colder climates, you’ll get a head start by starting seeds indoors six to seven weeks before your last frost date. In about four to five weeks, when the broccoli plants reach about 5 inches tall, harden them off so they are ready for transplanting. Broccoli can handle a slight frost once it’s hardened.
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.
Common Pests and Diseases
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.
Common diseases include blackleg, black rot, and clubroot. Disease control is best achieved by rotating the crop each year. Clubroot is diminished when you raise the soil pH to about 7.0.