The Cool-Season Vegetable Garden: Broccoli
By Vincent Lazaneo
Every cool-season garden should include some broccoli. This tasty and nutritious vegetable is low in calories and high in fiber. Broccoli is a good source of A and B vitamins and a half cup serving contains more vitamin C than an orange. It is also a good source of calcium, phosphorus and iron.
Broccoli and other cole crops (Brussels sprouts, cabbage, cauliflower, Chinese cabbage, collards, kale and kohlrabi) grow best from fall to spring with temperatures 40-65 degrees F. A period of warm weather above 70 degrees and long days cause plants to quickly flower (bolt) and go to seed.
Modern broccoli produces large blue-green heads on plants 24 to 30 inches tall. Dwarf varieties reach a height of 15 to18 inches. Sprouting broccoli produces a small main head about 3 inches across and many lateral shoots.
To Plant and Grow
Plants can be started from seed planted directly in the garden or in containers. A plant can be grown in a pot one foot wide and deep. Plant seed ¼ inch deep. Sow two or three seeds in groups about a foot apart. When seedlings have three or four true leaves, keep the most vigorous plant in each group and remove the others by cutting the stem with scissors.
Local nurseries also sell small plants, mainly in the fall. Set transplants in the soil at the level of the first set of leaves about ½ to one inch deeper than they grew in the container. Roots will form along the stem and help keep the plant erect.
Grow broccoli in well drained soil where it will receive full sun. Prepare soil for planting by digging to a depth of 8to12 inches. Mix in compost and a complete fertilizer. A slow-release fertilizer like Osmocote 14-14-14 is good for containers which require frequent irrigation. Soluble fertilizers cost less and work well in garden beds. Evenly apply one pound 10-10-5, 12-12-12 or similar fertilizer to 32 square feet of garden soil (4 foot by 8 foot garden bed). If you use manure, use a packaged product and apply 5 pounds of steer or one pound of poultry manure evenly to five square feet of soil. Mix manure in at least two weeks before planting and water well to leach excess salts from the surface soil. If you use a soluble pre-plant fertilizer or steer manure, you should apply additional nitrogen during the growing season. Scatter one or two teaspoons of ammonium sulphate (21 percent N) around each plant a few inches away from the stem every three weeks. Water well after application to carry the fertilizer into the soil.
Wet the soil at least 6 inches deep before seeding. When the surface begins to dry, plant the seeds then keep the surface damp with light watering until seeds sprout. Water transplants daily for the first week, then often enough to keep the soil moist but not soggy. Broccoli roots grow mainly in the top 6 inches of soil and established plants should be watered when the top inch begins to dry.
Several insect pests may feed on broccoli. Inspect plants often. A few aphids on young leaves can be gently rubbed off with a finger. Sturdy plants can be washed with a forceful spray of water.
Hand pick caterpillars or treat plants with an organic product containing the bacteria Bt. Also check plants for a new pest, the Bugrada bug and treat apply an insecticide early to protect plants from severe damage.
Harvest broccoli when the head is full but before flower buds start to open. Cut the stem with a sharp knife 4 to 6 inches below the head. Wash heads thoroughly to remove soil and small insects.
The tender stem can be peeled and cooked like the head or sliced and eaten raw. Heads taste best eaten fresh. They can be stored in the refrigerator for 5 to7 days but some vitamins will be lost and the stem will become tough.
Vincent Lazaneo is Urban Horticulture Advisor for UC Cooperative Extension. He helped found the San Diego County Master Gardener Association more than two decades ago and serves as its advisor. He is the author of numerous articles on plants and pests that appeared in the San Diego Union-Tribune, California Garden and other publications.
Broccoli Bowl Quiz
Answer true or false.
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