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Broccoli for Cool Weather Harvest

Broccoli central flower head
Broccoli head florets are tight
Harvest broccoli heads when florets are still beaded and tight.

Broccoli is best—bigger and most flavorfully sweet—when it reaches maturity in cool weather.

Mid- to late-summer is a good time to plant broccoli—the cool days and nights of autumn will arrive in the weeks before the tight florets of broccoli are ready for cutting. Broccoli is frost tolerant—so even if it turns unexpectedly cold, you will have a tasty crop.

Spring planted broccoli must come to harvest in cool weather as well. If you plant broccoli in spring, be sure to allow enough time for the variety you grow to reach harvest before days grow long and warm. Spring planted broccoli can be bitter if very warm temperatures arrive too soon.

Start fall broccoli 10 to 12 weeks before your average first frost date in fall; protect plants with row covers if the weather turns frosty. Spring broccoli should reach harvest before daytime temperatures reach the mid-60s°F consistently; protect young seedlings from frost with row covers to get them started in the garden early.

Broccoli can be direct seeded, but for fall planting start plants in peat pots and then transplant seedlings into the garden filling spaces vacated by warm-weather crops as they finish their season.

For a sustained harvest choose broccoli varieties with good sideshoot production—they will keep producing after the main stalk or shoot has been harvested–or plant several varieties with differing days to maturity. (Broccoli has a branching habit. It grows 2 to 3 feet tall and forms a central stalk on which will grow its main edible  flower or head; when the central flower is cut away, side branches, called sideshoots, lengthen and produce small flower heads, which are also edible.) Hybrid varieties are a good choice if you want an all-at-once harvest; they are more uniform than open-pollinated varieties that have less-uniform maturity rates.

Choose between heading-type broccoli which forms one large head of flower buds on a central stock (some heading varieties will produce sideshoots once the central head is cut), or sprouting-type varieties which form a lot of button-sized small florets in leaf axils. A dozen plants will feed a large family.

Whichever type broccoli you choose, keep in mind that one cup of cooked broccoli has more vitamin C than an orange and as much calcium as ¼ cup of milk; broccoli is also a good source of vitamin A, potassium, folate, iron, and fiber.

More tips at How to Grow Broccoli.

Broccoli Growing Tips:

Fall-harvest planting time. Sow broccoli 85 to 100 days before the average first fall frost—that will be in mid- to late-summer in most regions. If you are growing broccoli from starts or transplants just count backwards from the average first fall frost the number of days to maturity that you see on the plant label.

Site and soil. Plant broccoli in full sun in slightly acidic soil (pH between 6.0 and 6.8). Turn 2 to 4 inches of well-aged compost and a thin layer of aged manure into the planting bed before planting.

Spacing. Space plants 15 to 18 inches apart in intensively planted beds, 18 to 24 inches apart in rows with rows 24 to 36 inches apart. Set transplants slightly deeper in the ground than they were in the pot.

Feeding and watering. Feed seedlings with liquid fish-and-seaweed fertilizer. When broccoli forms heads feed plants compost tea to help maximize production. Add ½- to 1-inch of compost to the garden bed once plants are established. Give broccoli regular watering for best growth.

Harvest. Harvest broccoli when heads or sideshoots begin to swell and are firm, green, and beaded up—meaning the florets are still close and tight and yellow flower petals have not begun to show. When the head start to separate, buds will quickly begin to flower. Harvest the central head first; encourage extended side-shoot production by adding a sidedressing of fish meal or aged manure around the base of the plant. Florets will quickly flower in warm weather; quickly remove opening flowers so that the plant will grow more sideshoots. Harvest the central head by cutting the stalk at a slant about 5 to 8 inches below the head. This encourages side shoots. Cut heads in the morning when plants are cool for best flavor.

Protect against cold. Freezing weather will cause broccoli buds to turn purple and can soften the heads—but the flavor will not be adversely affected. Protect against freezing temperatures by placing a floating row cover over plants; this will keep heads 4° to 8°F warmer and extend the harvest by three or four weeks. A plastic tunnel or coldframe can add 10° to 30°F to daytime temperatures.

Pests. Broccoli can be attacked by a host of pests: Cabbage loopers will eat broccoli from the undersides of leaves. Handpick loopers as soon as you spot them or spray with Bacillus thuringiensis, a biological insecticide. Flea beetles can attack early plantings; exclude them with row covers. Cabbage-root maggots attack at ground level; use paper collars thrust into the soil around the base of plants. Aphids can be sprayed away with water or use insecticidal soap for large infestations.

Preparation. Soak harvested florets in salted water to remove insects hidden in heads.

Cooking. Serve broccoli raw in salads or dips or as a snack. Steam or blanch broccoli until it is tender crisp and still bright colored (just 5 to 10 minutes); for best flavor do not overcook broccoli. Serve broccoli with a squeeze of lemon or vinaigrette.

Broccoli Varieties to Grow:

  • Arcadia: hybrid; 63 days to maturity; frosty blue-green heads about 8 inches across followed by numerous side shoots; disease resistant and heat and cold tolerant.
  • Calabresse: open-pollinated; 58 to 80 days to maturity; great tasting Italian heirloom produces tight, dark-green heads 3 to 6 inches across followed by numerous sideshoots; disease resistant; likes cool weather.
  • DeCicco: open-pollinated; 48 to 65 days to maturity; tasty Italian heirloom with small central heads 3- to 4- inches across; compact plant produces big harvest.
  • Early Purple Sprouting: open-pollinated; 220 to 250 days to harvest; sprouting type English heirloom with numerous sideshoots; overwinters well in mild regions; plant in summer for harvest next spring; hardy to below 10°F.
  • Flash: hybrid; 50 days to maturity; sweet tasty flavor, early to harvest with deep green, 6-inch heads of tight beads; good sideshoot production following central head; disease and heat resistant.
  • Green Goliath: open-pollinated; 55 days to maturity; large blue-green, domed heads with tight beads, very flavorful; very good sideshoot production.
  • Gypsy: hybrid; 58 days to maturity; medium green, well-domed heads; great flavor, uniform yield; heat- and disease-tolerant.
  • Marathon: hybrid; 62 to 68 days to harvest; large, blue-green heads with fine beads; good sideshoot production; widely adapted; very good cold tolerance; disease- and heat-tolerant.
  • Packman: hybrid; 55 days to maturity; tightly set beads on 8-inch domed head; yields smaller heads after main head is cut; heat tolerant.
  • Premium Crop: hybrid; 58 to 62 days to maturity; delicate flavor; deep blue-green heads 9- to 10-inches across, well-domed with fine beads; good sideshoot production in fall; disease- and heat-tolerant.
  • Rosalind: open-pollinated; 60 to 65 days to maturity; violet-purple heads 6- to 8-inches across; emerald green when cooked; heat-tolerant, best production in cool weather.
  • Umpqua: open-pollinated; 55 to 60 days to maturity; sweet, tender flavor; large central, well-domed head with fine beads followed by numerous sideshoots.
  • Waltham 29: hybrid; 60-95 days to maturity; large, 4- to 6-inch, blue-green heads; very good sideshoot production; good for fall growing, withstands very cold temperatures.

More tips at How to Grow Broccoli.

Written by Stephen Albert

Stephen Albert is a horticulturist, master gardener, and certified nurseryman who has taught at the University of California for more than 25 years. He holds graduate degrees from the University of California and the University of Iowa. His books include Vegetable Garden Grower’s Guide, Vegetable Garden Almanac & Planner, Tomato Grower’s Answer Book, and Kitchen Garden Grower’s Guide. His Vegetable Garden Grower’s Masterclass is available online. Harvesttotable.com has more than 10 million visitors each year.

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