How to Grow Broccoli

If you enjoy vegetable gardening or are thinking of giving it a try, consider broccoli (Brassica oleracea var. botrytis) as a possible crop. A tough, easy-to-grow plant, broccoli is grown as an annual in all parts of the United States, although it might survive winter in U.S. Department of Agriculture plant hardiness zones 7 through 11. It only needs a sunny spot and basic care to thrive, but produces the best heads when grown in cool weather.

You can plant broccoli whenever weather is likely to stay cool for a couple of months, either in spring or fall. For spring planting, sow seeds indoors about six weeks before you plan to move them outdoors, or purchase seedlings from a garden center in early spring. Hot weather stresses plants and can cause bitter-tasting or loose heads, so if spring in your area tends to be short, you can also plant broccoli for a fall harvest. Sow seeds directly in the garden in mid-summer, about three months before you want to pick heads, or purchase transplants and set them into the ground in late summer. For large heads, give young plants lots of room, spacing seedlings or thinning sprouts to allow 18 to 24 inches between plants, with 3 feet between rows.

Growing in a spot that gets full sun helps speed broccoli plants to maturity. But if your area tends to have warm periods in spring or fall, giving the plants some light afternoon shade helps prevent bolting, or going to seed before strong heads form. Broccoli plants need soil that's high in organic matter for best growth. When you're ready to plant, you can improve your soil's organic content by covering your planting area with 2 or 3 inches of compost and turning it into the soil with a garden fork. Broccoli also needs well-drained soil and does poorly in soil that tends to stay soggy after rain or watering. If your soil contains clay and drains slowly, add some coarse sand before planting to improve its drainage.

Broccoli plants are heavy feeders that thrive when given fertilizer at intervals during their growth. Add about 3 pounds of a low-nitrogen, 5-10-10 formula for each 100 square feet of area at planting or seeding, then side-dress about 3 weeks later or when sprouts are at least 6 inches tall, using a 33-0-0 fertilizer at a rate of 1 pound per 100 feet of row. To side-dress, mix fertilizer gently into a shallow trench about 8 inches away from the stems of your plants, taking care not to disturb their roots. Broccoli plants also need uniform moisture to produce a good crop. During dry spells, provide extra water, aiming for 1 inch weekly including rain, but water in the morning to allow foliage to dry before night arrives and ensure that soil is moist to a depth of at least 6 inches after you water.

Broccoli plants are susceptible to a number of pests that can damage plants and interfere with production of good heads. Several types of cabbageworms can cause problems by chewing holes in leaves and developing heads. Hand-pick these pests, which are soft-bodied and can be green or brown, whenever you see them. Using floating row covers on a small planting can also help keep these and other pests, such as flea beetles and aphids, from infesting broccoli plants. Washing plants with a strong stream of water every few days can also remove small pests, but do this early on a sunny day so plants dry quickly. Few diseases cause significant damage to broccoli plants, but black rot can occasionally cause wilting and blackening of leaves. It's best prevented by planting in an area with good air circulation, keeping foliage dry and regularly clearing away debris from under the plants.