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Cauliflower Growing Problems: Troubleshooting

Cauliflower plant1
Cauliflower plant
Cauliflower Problems can be avoided: Summer-planted cauliflower for fall harvest will be both easier to grow and more flavorful–cauliflower prefers to leisurely mature in cool weather.

Cauliflower is grown much like cabbage, but requires more careful treatment. It is best to start cauliflower indoors where it can be protected from both cold and hot temperatures.

Spring-planted cauliflower is likely to face early cold and late heat which will make the effort difficult.

Summer-planted cauliflower for fall harvest will be both easier to grow and more flavorful–cauliflower prefers to leisurely mature in cool weather.

Start the fall cauliflower crop at the same time you plant late cabbage

For cauliflower growing tips see Cauliflower Growing Success Tips at the bottom of this post.

Common cauliflower growing problems with cures and controls:

• Seedlings fail to emerge from soil; seedlings are eaten; roots are tunneled. Cabbage maggot is a small gray-white, legless worm to ⅓-inch long; adult is the cabbage root fly, 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. Companion plant with mint.

• 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 soil is well drained.

• Seedlings are eaten or cut off near 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 base of plants

• Young sprouts fail to grow or die back; bluish-black spot on leaves and stems. Blackleg is a fungal disease which leaves sprouts girdled and rotting 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 planting bed; make sure soil is well-drained. Rotate crops.

• Young plants flower. Cold will cause young plants to 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. Don’t plant too early.

• 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 resistant varieties. Rotate crops. Keep garden free of plant debris.

• Plant wilts; roots are swollen and misshapen, 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 soil pH below 7.2. Rotate crops for at least 2 years. Purchase transplants from disease-free supplier.

• Leaves become dull yellow, curl, and plant may die. Cabbage yellows is 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 resistant varieties: Early Snowball.

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

• Plant stunted; worms tunnel into roots. Plump grayish grub with 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 soil before planting; hand pick 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.

• 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 garden free of crop residue and weeds where bugs breed. Spray plants wit 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.

• Tiny shot-holes in 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 roots of germinating plants. Spread diatomaceous earth around seedling. Handpick off plants, Cultivate often to disrupt life cycle. Keep garden clean. Spade garden soil deeply to destroy larvae in earl 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. 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 garden clean of debris where adult brownish night-flying moth 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. 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; tunnels inside cabbage and cauliflower heads. 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. 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 over-head watering. Rotate crops.

• Scorched leaf margins. Molybdenum deficiency in very acid soil. Test soil. Apply lime to produce a neutral soil, pH 6.0 to 7.0. Add about ½ ounce of ammonium molybdate per 500 square feet. Plant resistant varieties: Snowball X, Snowdrift, or Snowball Y.

• Curds gradually turn brown. Boron deficiency, often found in alkaline soils. Test soil. If deficient, add ½ ounce of borax per 24 square yards.

• Heads are loose and yellowish. Too much sun. Lift and tie leaves over the developing heads. Grow plants so that they mature in the cool, moist weather of autumn.

Cauliflower Growing Success Tips:

Planting. Grow cauliflower in well-drained soil rich in organic matter. Plant cauliflower in full sun in cool regions; where the weather is warm plant cauliflower in afternoon shade. Start cauliflower indoors and transplant it out into the garden about 4 to 5 weeks after seedlings emerge. Seedlings started indoors in early spring should be hardened off before they go into the garden; set seedlings outside for a few hours each day for a week or so before transplanting them out.

Planting time. Cauliflower grows best in cool weather. Transplants can be set in the garden as early as 1 to 2 weeks before the average last frost date in spring; set cauliflower in the garden when the soil temperature has warmed to 55°F and daytime temperatures average in the 50°s and 60°sF. If spring weather warms too quickly, spring planted cauliflower may bolt and flower prematurely. A summer-planted fall crop is a safer bet: sow cauliflower in the garden about 75 days before the average first frost date in autumn. Mulch summer-planted cauliflower to help keep the soil evenly moist and cool. Where winter temperatures stay mild, cauliflower can planted in autumn and grown through the winter for spring harvest.

Care. Keep cauliflower evenly moist; do not let the soil dry out. Side dress cauliflower with compost tea every 2 to 3 weeks during the growing season. Mulch cauliflower beds to keep the soil cool and conserve soil moisture.

Harvest. Cut cauliflower heads before they get too big, when they are about 6 inches across, slightly larger than a softball.

More tips: How to Grow Cauliflower.

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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  1. One of my potted young cauliflower started growing the root ball above the soil line. The stems and leaves grew fine, then the ball split and the stems fell. What happened? I have 3 others and they are fine. Thanks

    • Roots seeking oxygen and water will grow above the soil line if the soil is too compacted. Use commercial potting soil or seed starting mix to prevent the soil from compacting or add vermiculite to the soil you are using.

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