Broccoli Growing Problems and Solutions -- Harvest to Table

Grow broccoli as you would cabbage. Grow broccoli as rapidly as possible. Give broccoli plenty of moisture and be sure to feed it through the season–a planting bed amended with aged compost is an important start. While broccoli is hardy at maturity, young plants should not be subjected to frost.

Here are common broccoli-growing problems with cures and controls:

Table of Contents

Seeds and seedlings

Seedlings fail to emerge from soil; seedlings are eaten; roots are tunneled

A cabbage maggot is a small gray-white, legless worm to ⅓-inch long; an adult is the cabbage root fly, which looks like a housefly. Flies lay eggs in the soil near the seedling or plant. Maggots will tunnel into roots leaving brown scars; some plants may be honeycombed with slimy tunnels. Exclude flies with floating row covers. Remove and dispose of damaged plants. Apply lime or wood ashes around the base of plants; time planting to avoid insect growth cycle. Plant a bit later when the weather is drier.

Seeds rot or seedlings collapse with dark water-soaked stems as soon as they appear

Damping off is a fungus that lives in the soil, particularly where humidity is high. Do not plant in cold, moist soil. Make sure the soil is well drained.

Seedlings are eaten or cut off near the soil level

Cutworms are gray grubs ½- to ¾-inch long that can be found curled under the soil. They chew stems, roots, and leaves. Place a 3-inch paper collar around the stem of the plant. Keep the garden free of weeds; sprinkle wood ash around the base of plants.

Young sprouts fail to grow or die back; bluish-black spot on leaves and stems.

Blackleg is a fungal disease that causes sprouts to girdle and rot at soil level–“blacklegs.” Blackleg is spread by cutworms and cabbage maggots. Remove and destroy infected plants; keep the garden free of plant debris. Add organic matter to the planting bed; make sure the soil is well-drained. Rotate crops.

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Irregular yellowish to brownish spots on upper leaf surfaces; grayish powder or mold on undersides

Downy mildew is caused by a fungus. Improve air circulation. Plant disease-resistant varieties. Rotate crops. Keep the garden free of plant debris.

Leaves become dull yellow, curl, and plants may die

Cabbage yellows are caused by the Fusarium soil fungus that infects plants usually where the soil is warm. The disease is spread by leafhoppers. Remove infected plants. Control leafhopper. Keep the garden free of weeds which can harbor disease. Keep soil evenly moist, but not wet. Rotate crops. Plant disease-resistant varieties such as Early Snowball.

Leaves yellow; plant stunted; small glistening white specks on roots

A root cyst nematode is a microscopic worm-like animal that lives in the film of water that coats soil particles. Rotate cabbage family crops. Solarize the soil with clear plastic in mid-summer.

Leaves are yellowish and slightly curled with small shiny specks

Aphids are tiny, oval, whitish-green, pink, or black pear-shaped insects that colonize on leaves. They leave behind sticky excrement called honeydew which can turn into a black sooty mold. Remove with a blast of water. Use insecticidal soap solution. Mulch with aluminum foil to disorient aphids.

Leaves have whitish or yellowish spots; leaves are deformed; plant wilts

Harlequin bugs or stink bugs. Harlequin bugs are black with bright red yellow or orange markings. They suck fluids from plant tissue causing white and yellow blotches. Handpick and destroy bugs and egg masses. Keep the garden free of crop residue and weeds where bugs breed. Spray plants with Sevin, pyrethrum, and rotenone. Stink bugs are gray or green shield-shaped bugs about ¼-inch long; they feed on fruits. Remove garden debris and weeds where bugs can overwinter. Hand-pick egg masses and bugs and destroy them.

Tiny shot holes in the leaves of seedlings

Flea beetles are tiny bronze or black beetles a sixteenth of an inch long. They eat small holes in the leaves of seedlings and small transplants. The larvae feed on the roots of germinating plants. Spread diatomaceous earth around seedlings. Handpick off plants, Cultivate around plants often to disrupt the beetles’ life cycle. Keep the garden clean. Spade garden soil deeply to destroy larvae in early spring. Treat plants with Sevin, pyrethrum, or rotenone.

Leaves partially eaten; leaves webbed together; eggs in rows on undersides of leaves

Cabbage webworms are green with a light stripe to ¾ inches long; the webworm is the larvae of a brownish-yellow moth with gray markings. Larvae spin light webs. Clip off and destroy webbed leaves. Destroy caterpillars. Keep garden weed free.

Leaves are eaten and plants are partially defoliated

Blister beetles are slender gray or metallic black beetles to ¾-inch long; they may have striped spots on their wings. Handpick beetles and destroy them. Keep the garden weeds and debris. Cultivate in spring to kill larvae and interrupt the life cycle. Spray or dust with Sevin or use a pyrethrum or rotenone spray.

Large holes in leaves; leaves skeletonized. Cabbage loopers or armyworms. (1) Cabbage looper is a light green caterpillar with yellow stripes running down the back; it loops as it walks. Keep the garden clean of debris where adult brownish night-flying moths can lay eggs. Cover plants with spun polyester to exclude moths. Pick loppers off by hand. Use Bacillus thuringiensis. Dust with Sevin or rotenone. (2) Armyworms are dark green caterpillars the larvae of a mottled gray moth with a wingspan of 1½ inches. Armyworms mass and eat leaves stems, and roots of many crops. Armyworms will live inside webs on leaves. Handpick caterpillars and destroy them. Cultivate after harvest to expose the pupae. Use commercial traps with floral lures.

Leaves are chewed and slimed

Snails and slugs eat leaves. Collect these pests at night. Set beer traps at soil level to attract and drown snails and slugs.

Leaves chewed

Imported cabbage worm is a pale green caterpillar with yellow stripes to about 1¼ inches long; the adult is a white moth with two or three black spots on the forewing. Use Bacillus thuringiensis. Destroy all remains and weeds after harvest. Companion plant with mint. Encourage the predatory Trichogramma wasp.

Leaves and head become pale green; leaves wilt; slimy rot develops in stem, leaves, and head.

Bacterial soft rot is caused by Erwinia bacteria. Water-soaked spots appear on leaves and roots; spots enlarge and turn dark and mushy. Black ooze develops in cracks in roots and stems. Rot can not be cured. Collect and burn infected plants Promote good drainage by adding aged compost and organic materials to planting beds. Avoid overhead watering. Rotate crops.

Whole plant problems

Plant wilts; roots are swollen and misshapen, and roots rot

Clubroot is a soilborne fungal disease. Fungus interferes with water and nutrient uptake of roots. Keep the garden clean of plant debris and weeds that can harbor the fungus. Remove and destroy infected plants including soil around roots. Clubroot is found in acid soils; add lime if the soil pH is below 7.2. Rotate crops for at least 2 years. Purchase transplants from disease-free suppliers.

Plant stunted; worms tunnel into roots

Plump grayish grub with a brown head is the larva of the June beetle, a reddish brown or black hard-shelled beetle to 1 inch long. Wireworms are the soil-dwelling larvae of click beetles; they look like wiry-jointed worms. Check the soil before planting; handpick and destroy pests; flood the soil if wireworms are present. Remove infested plants and surrounding soil. Keep the garden free of refuse that could shelter beetle eggs.

Plant stops producing heads or buds; older buds flower

Harvest heads regularly, at least every 3 days. If buds are allowed to flower, the plant will stop producing new heads.

Plant suddenly flowers

Warm temperatures over 85°F will trigger flowering, and small yellow flowers bloom. Plant earlier so that the plant matures before the heat of summer arrives. Plant mid-summer for a fall crop; plant matures in cool weather. Plant early-maturing varieties: Green Comet Hybrid, Spartan Early, Premium Early.

Small scattered heads form; mature heads do not

Young plants will form small heads prematurely if temperatures fall below 40°F shortly after planting. Protect young plants with hot kaps or floating row covers.

Young plants flower

Cold will cause young plants to prematurely flower and produce seed without forming a head. Protect young plants from cold weather with floating row covers; set transplants into the garden no sooner than 1 to 3 weeks before the last average frost date in spring.

Broccoli growing success tips

Planting

Broccoli is a cool-season crop. Plant broccoli in full sun where temperatures do not exceed 80°F. Where temperatures are warmer, grow broccoli in partial shade. Grow broccoli in well-drained soil rich in organic matter. Add aged compost to the planting bed before planting. Broccoli can be sown directly in the garden but is best started indoors where it can be protected from early temperature fluctuations and pests.

Planting time

Sow broccoli indoors as early as 6 to 8 weeks before the average last frost date in spring. Set plants in the garden as early as 2 weeks before the expected last frost. Plant early: warm weather in late spring will cause plants to bolt and flower. As well, weather too chilly in spring–just three or four days below 50°F–will cause broccoli to form button-like flower heads that will never develop. Do not plant out broccoli until the weather is settled. For a fall crop, sow broccoli in the garden 10 to 12 weeks before the average first frost in fall. Protect mid-summer planted broccoli from the heat by planting taller crops such as tomatoes or corn. In late fall, use floating row covers to protect maturing broccoli from temperatures in the 20°sF.

Care

Keep broccoli evenly moist; do not allow the soil to dry out. Side-dress broccoli with compost tea about 2 weeks after transplanting into the garden. Later, side dress plants with aged compost when the main flowerhead begins to form.

Harvest

Broccoli will be ready for harvest soon after flower heads are 1 inch in diameter. Once the main flower head is harvested, broccoli will produce side shoots for up to 3 months. (For a sustained harvest, space broccoli plants at least 24 inches apart at planting time.)

Broccoli articles at Harvest to Table:

How to Plant and Grow Broccoli

Broccoli Seed Starting Tips

How to Harvest and Store Broccoli

Broccoli Growing Problems: Troubleshooting

Seven Ways to Cook and Serve Broccoli

How to Grow Broccoli Raab

Four Ways to Cook and Serve Broccoli Raab

More problem solving tips at:

Common Vegetable Garden Pests

Vegetable Garden Diseases Problem Solver

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