Problems Growing Cauliflower – Learn About Diseases Of Cauliflower

Problems Growing Cauliflower – Learn About Diseases Of Cauliflower

By: Amy Grant

Cauliflower is a member of the Brassica family that is grown for its edible head, which is actually a grouping of abortive flowers. Cauliflower can be a little finicky to grow. Problems growing cauliflower may arise due to weather conditions, nutrient deficiencies and cauliflower diseases. Knowing what type of cauliflower diseases may afflict the veggie and troubleshooting these cauliflower problems will aid in the healthy production and yield of the plant.

Diseases of Cauliflower

Knowing diseases of cauliflower can also help with your other cruciferous crops, such as cabbage and rutabaga. Diseases may be caused by viruses, bacteria, and fungi.

  • Alternaria leaf spot, or black spot, is caused by Alternaria brassicae. This fungus presents as brown to black ringed spots on lower leaves of the cauliflower. In its advanced stage, this fungal disease turns the leaves yellow and they drop. While Alternaria leaf spot primarily occurs on leaves, the curd may be infected as well. The disease is spread by spores that are spread by wind, splashing water, people and equipment.
  • Downy mildew is also caused by a fungus, Peronospora parasitica, which attacks both seedlings and mature plants. It is seen on the upper surface of the leaf as small yellow spots that eventually turn brown. On the underside of the leaf, white downy mold appears. Vascular discoloration may also occur. Downy mildew also acts as a vector for bacterial soft rot.
  • Bacterial soft rot is an odiferous condition that presents as small water soaked areas that expand and cause the plant’s tissue to become soft and mushy. It enters through wounds caused by insects or damage caused by machinery. Humid and wet conditions encourage the disease. Space plants to allow for air circulation and avoid sprinkler irrigation. Take care when working around plants with tools or machinery. Seeds may also be treated with hot water to kill black rot and other bacterial infections. Also, use disease resistant seed when possible.
  • Blackleg is caused by Phoma lingam (Leptosphaeria macutans) and is a major scourge in cruciferous vegetables. The fungus remains in cruciferous veggie detritus, weeds and seeds. Again, wet weather is a major factor in the spread of the spores of blackleg. Afflicted seedlings are killed off by this disease, which presents as yellow to brown spots with gray centers on the leaves of the plant. Hot water or fungicide can control blackleg, as can limiting work in the garden during wet periods. If the infection is severe, do not plant any cruciferous crops in the area for at least 4 years.

Additional Cauliflower Diseases

  • Damping off is caused by the soil fungi Pythium and Rhizoctonia. Both seed and seedlings are attacked and rot within a few days. Older plants afflicted with Rhizoctonia end up with wire-stem, a condition where the lower stem becomes constricted and dark brown at the soil surface. Use treated seed, pasteurized soil and sanitized equipment to thwart damping off disease. Don’t overcrowd seedlings or overwater. Sow in well-draining medium.
  • Yet another cauliflower disease is clubroot, which is caused by Plasmodiophora brassicae. This destructive soil borne disease affects many wild and weed members of the cabbage family. Entry of the fungus via the root hairs and damaged roots rapidly accelerates. It causes abnormally large taproots and secondary roots, which then decay and release spores that can live for a decade in the soil.
  • Fusarium yellows or wilt symptoms are akin to those of black rot, although it can be distinguished because leaf dieback progresses from the petiole outwards. Also, afflicted leaves usually curve laterally, leaf margins often have a reddish-purple streak and dark discolored vascular areas are not representative of Fusarium yellows.
  • Sclerotinia blight is caused by Scierotinia sclerotiorum. Not only cruciferous crops are susceptible, but many other crops like tomatoes. Windblown spores attack both seedlings and mature plants. Water soaked lesions appear on the plant and the affected tissue turns grey, often accompanied by a fluffy white mold dotted with hard, black fungus called sclerotia. In the final stages, the plant is dotted with pale grey spots, stem rot, stunting and eventual death.

Troubleshooting Cauliflower Problems

  • If possible, plant disease resistant seeds. If that isn’t possible, pre-treat seeds with hot water to kill bacterial infections.
  • Don’t use old seeds or improperly stored seeds, which will produce weak plants susceptible to disease.
  • Avoid damaging cauliflower plants.
  • Practice crop rotation to prevent the common diseases of cauliflower. This includes avoiding the planting of any of cauliflowers relatives (such as broccoli, cabbage, Brussels sprouts or kale) for at least three years.
  • Lime the soil to prevent fungal infections.
  • Use only new or sterile flats and tools.
  • Allow plenty of space between seedlings to foster good air circulation.
  • Avoid watering from above, which will spread potential spores more easily.
  • Remove and destroy seedlings that show signs of infection.

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Troubleshooting Cauliflower Problems: Tips On Treating Cauliflower Diseases - garden

A lot of problems can happen in the garden that can confuse the average gardener. From germination, wilting, light conditions, diseases, watering, pest and much more! Below is an explanation for some of the most common problems that gardeners and farmers face when planting vegetable seeds.

Identifying and Treating Diseases

Seeds Do Not Germinate

Learning Download: Germination

This is a tricky one. Most of the time it will be an environmental condition and not the seeds. Most professional seed companies will not send seed that has been professionally tested at 85% germination. If it is just one seed variety then it may be the seed but if you have trouble with more than one it is most likely an environmental control.

Replant and make sure soil drains well

Replant and protect seed. Relocate

Seedling Wilt and Die

Learning Download: Wilt

Seedlings can be very fragile. Keeping healthy growing conditions can be a challenge for people who work, have children or just don’t have time.

Keep soil moist but not dry or damp

Usually causes root rot and plant dies where stem meets the soil

Seedlings don’t need fertilizer the first month of growth. Use a soiless mixture to start seeds

Treat with organic insecticide

Spindly and Reaching Plants

Learning Download: Spindly Plants

This is one of the most common occurrences for beginning gardeners. Tomatoes, peppers, and other vegetable stems will get long and skinny as though they are reaching for more light.

Use grow lights or sunny location. Do not burn plants.

Slow watering. Improve drainage.

Thin plants out. Increase spacing.

Do not fertilize seedlings.

Slow Growth

Learning Download: Slow Growth

Slow growth of vegetables plants can be a number of factors. Sometimes it can just be the nature of the plant to grow slow, other times it may be transplant shock.

Most vegetables need full light. Move to new location.

Use row covers or cloths to protect from cold.

Identify insect doing damage and remove pest.

Yellow Leaves

Learning Download: Yellow Leaves

Yellow leaves is a common problem on tomatoes for gardeners. It will affect other vegetables and usually means the same thing.

Most vegetables need full light. Move to new location.

Poor Yields

Learning Download: Poor Yield

Poor yields can be attributed to several things that go wrong in the garden.

Temperature too hot or cold. Grow varieties that are right for your climate.

Test soil, fix as needed. Too much nitrogen

Reader Interactions


that was really nice to read this blog .. that was great..

I have squash and cukes in my florida garden. Both have bloomed well but neither one has developed anything. Help.

Squash and cucumbers plants produce male flowers first, followed by female flowers. The female flowers will have tiny fruits at their base–that’s how you can tell them apart from the males. Insects pollinate the blossoms, but they must visit both the male and female flowers. If the weather is cloudy or cool or rainy, the insects may not be active. If only male flowers have appeared, wait a few days and the females will follow–and the insects can do their job of pollination. If all else fails, you can hand pollinate the female flowers: use a cotton swab to transfer pollen from the male flowers to the female flowers. Or pick a male flower, pull off the petals, and rub the pollen directly on the stigma of the female flower.

I am having problems with my watermelon. It looks like end rot, like you see on a tomato. Will calcium help this problem?

Yes calcium and even watering will help. You can add crushed eggs to a watering can full of water or spread the crushed eggs around the plant stem and water. Or spread a fertilizer rich in calcium around the plant. Keep the soil evenly moist so that the plant cells grow uninterrupted.

My garden plants are not growing well, just not growing taller or developing well. Some tomatoes blooming, but growth very small. Pepper plants still very small. If I add organic compost or peat moss, should I do this right on top of the existing soil and just lightly turn it around the existing plants, or do I wait until this season is over and just start in the fall? I hate to waste the remainder of the season. THanks for any help!

You can either add the compost across the soil surface or turn it lightly under without disturbing plant roots. Irrigation or rain water will then carry the nutrients down to the feeding roots. Small fruit growth on tomatoes and peppers may be the result of cool days or cool nights as well.

I have a vegetable garden as well s many flowers. Last week as I was weeding, I found a huge jelly like substance around one of my celery plants. I dug this out and thought everything was okay. Today I noticed in a windowbox with flowers, the same jelly like substance around each flower and a bunch of flies all over the plants. What is this? And more importantly, how do I get rid of it?

Have you added a commercial potting mix or soil to your window boxes or planting beds that contains a moisture-retentive polymer? These ploymers soak up water and then slowing release back into the soil they have a clear jelly like appearance when hydrated.
Another possibility is slime molds, a single-celled organism, that lives on dead plant material, often in lawns or garden beds. If you suspect slime mold, take a sample to a nearby office of the state agriculture office for identification. You can dig around slime mold organisms and remove them from the garden and dispose of them, but the spores that begin their growth may remain in the garden and form new organisms.

My cucumbers have a mold on the leaves and my beans have shriveled leaves. what can I do to save them?

White patches on cucumber leaves is likely a sign of powdery mildew (white mold on fruits is likely southern blight or white mold). To control and kill fungal spores of powdery mildew get a fungal spray at the garden center or add a tablespoon of baking soda, 2.5 tablespoons of vegetable oil, and a teaspoon of liquid soap (not detergent) to a gallon of water and spray the plants.
Bean leaves that shrivel: the first thing to check is soil moisture–the soil should stay evenly moist early in the season when roots have not yet grown deep make sure your plants are getting water every couple of days. If watering is not the problem, then bacterial blight or mosaic virus may be attacking your plants–remove diseased plants and replant with disease resistant cultivars.

This is my first year doing a raised bed garden. We planted vegetable starts on March 16th. Nothing appears to be growing at all. Leaves are light green. Soil test showed extremely deficient in Nitrogen, Phosphorus, and Potassium. We dumped gallons and gallons of 20-20-20 on garden 4 days ago. Also, moisture tester shows moisture several days without water. Is our garden not draining properly? Redoing soil test again today for N,P,, and K. Any help would be greatly appreciated.

The slow growth may be linked to air or soil temperature. Seedlings demand warm temperatures to thrive they will linger or die if temperatures are too chilly–especially at night. If temperatures remain in the 50s or 60s at night you should consider placing spun poly row covers over the plants until temperatures warm. Your moisture meter will tell you if the soil is too wet or too try. Be careful adding too much fertilizer, especially nitrogen nitrogen can burn seedling roots. Light green leaves could indicate (1) cool air temperatures, (2) too much or too little moisture, (3) too little or too much nitrogen–that diagnosis may not be helpful but you can begin to eliminate possible cause one-by-one. Keep us posted on your progress.

My tomatoes are not growing well. They are in full sun, and watered regularly. The stems are dark and the leaves are pale. Anyone got a clue? It has been cool here at night last few days, but i dont think temp dropped below 60F at night. Thanks

Be sure you are not overwatering–tomatoes that have been in the garden a few weeks can be watered every three or four days. Allow the first inch of soil to dry before watering again. Pale leaves may also be an indication of pest insects feeding on the leaves check the undersides of leaves to be sure pest insects are not harboring there.

Squash plants- beautiful blossoms open, are pollinated ( I see bees inside ) and the next day fall off the plant. No fruit. any ideas? Would the male flowers just fall off the next day? I’ll try to see if they are male or female. could the plants be all males? Thank you!

Blossom drop can be caused by poor pollination–or no pollination. But blossom drop can also be caused by weather too hot or too cold, too much or too little water, or too much nitrogen in the soil. Blossom drop is often the result of environmental stress.

Good news- we worked some organic fertilizer into the soil- left for the weekend and came back to 5 or 6 growing squash. We are on the mend. Thank you for your insights- we are in CT(I should have mentioned that) and the weather has been dry, was cold and now hot etc.

Thanks for the follow up. Sounds like the plants are on the right track. Happy gardening!

really helped me on my project
Thank you

Thank you for reading Harvest to Table.

Im having an issue with my zucchini & Yellow squash. . . . The leaves have turned from dark green to a dusty gray color and the plants are dying. . . I dont know what to do about this. It seems to be spreading to other squash plants as well.
I use an organic oil based 3 in 1 garden spray. . . The bottle says for Insecticide, fungicide, miticide. ( ingredients are Sesame oil- 5%, Other ingredients Lecithin, edible fish oil, potassium sorbate, water – 95%) I add Neem oil and a tspn of liquid soap to the spray bottle when I mix it up. . . . . . I have used this spray on all my plants, but it is Not working on these squash. . . .

Squash and zucchini leaves turning a dusty gray indicate (as you note) the plants are in serious decline. The spray solution may be partially to blame if sprayed in the middle of the day the oil could exacerbate sunburn to leaf tissue. Generally, it’s best to try any spray on a few leaves before treating the entire plant. You could give the plants a compost-tea boost or feed the plants with a dilute fish emulsion drench at the base of the plants. That said, it may be too late for these plants. Plant seed or seedlings in another part of the garden there is still enough season to get a crop.

I have a garden with vegetables. My cucumbers and squash are loaded with littles. The zucchini get to about – 1/2” , the flower dries off and so does the zucchini . The yellow squash are doing the same. What is my issue?

As for my cucumbers, they have little cukes after about 1/2” to 1” they are turning yellow and drying up. What is my issue.

The baby squash and cucumbers are aborting. The likely cause is lack of or insufficient pollination. Early in the season this is not uncommon. Make sure you are attracting bees and other pollinators to the garden.

Wonderful post and such fantastic information that you gave to us. Thank you so much for it. You made a good site and also you sharing the best information on this topic. I am impressed with your site’s blog. Thank you.

Thanks for reading Harvest to Table and Happy Gardening!

Thank you for this blog! I have a couple questions. We live in the central valley California, daytime temps are around 90 to 100, evening temps 65-70.
We have a raise bed garden and a small inground garden too.
The small inground has two tomato plants, one is blooming ferociously and has a couple tomatoes that have matured well over the past two weeks but have ceased to continue to mature. The existing blossoms on this plant as well as the second plants bloom beautifully, begin to yellow as if they will fruit and then die and fall off. Both plants have strong structures & beautiful leaves – nearly without pest or blemish. I noticed plant number two is beginning to display some ‘curl’ on the larger leaves. Thoughts? TIA! Christine

Oops!! PS: plant 2 has no fruit

The daytime temperatures are too hot most vegetables will stop growing and be dormant until temperatures fall back into the 80s every day the flowers fail because of the heat as well. Keep the soil just moist, shield the plants from the mid-day sun, and wait for temps to moderate–then the plants will continue to grow and set fruit.

I have these Mandarin trees which are drying up. Have observed that on removing the bark from the main stem just beneath the soil are all dried up from within. Please help

My Zucchini Plants looking fine but I got only finger size Zucchinis. My Eggplants plants are looking good, but the fruits themelves grow just one third the size and the skins taste leathery. Too little water, too much water, too little fertilizer, too much fertilizer or what?

It is likely the plants are small and stressed from too little water. Keep the soil evenly moist–it should be moist 3 inches below the surface this time of year. Feed the plants a dilute solution of fish emulsion or kelp meal every 10 days.

Hello there, my long squash or opa plants are well bloomed and leaves are all healthy. But opa squash fruit size is only finger size and not growing and some are half way through turning brown and burning. Donot know what to do. Please help

If temperatures are hotter than 87F there is not much to be done but wait for temperatures to moderate. Keep the soil evenly moist, do not let it dry out feed the plant with a dilute solution of fish emulsion every 10 days.

2. Bolting

When a plant bolts, it “runs to seed,” halting growth in its tracks. It’s not uncommon during the early vegetative stage.

What It Looks Like

A center stalk forms, flowers, and sets seed. Once this happens, it will never form a head.


A sudden spike or dip in temperature early in the plant’s development may induce it to fast-forward to the end of its life cycle.

This is especially likely to occur if seedlings are transplanted to the garden too early in spring, when the weather is still cold.

Avoidance Measures

Make sure the seeds you sow are suited to your region. The days to maturity must match the length of your growing season, whether it’s spring, fall, winter, or all three.

Start seeds indoors, not only to get a jump on the growing season, but to protect them from the chance of a late-spring freeze.

Provide protection in the form of floating row covers, mulch, and shade cloth when weather predictions warrant them.

In the event of a heatwave, take extra care to ensure that plants don’t dry out which causes additional stress. Keep the soil moist but not waterlogged.

3. Blackleg

Blackleg is caused by the fungus Leptosphaeria maculans, aka Phoma lingam, that produces fruiting bodies called pycnidia and pseudothecia.

They contain microscopic spores that are dispersed on the wind when the temperature is between 65 to 80°F and conditions are wet.

The disease may be present in seeds, as well as in plants that develop cracks from especially cold weather, injury, or insect damage.

Warning Signs of Blackleg

The first indications are tan-colored spots on the leaves. Gradually they darken to gray with black dots.

As the disease progresses, the stems may develop lesions, or “cankers,” with dark black to purple margins. The damage may move down the stems to the roots, blackening tissue as it progresses.

To Avoid Blackleg

If seed is not certified disease-free, you may treat it with hot water before planting by soaking seeds for 15 to 30 min at 122°F.

Don’t plant during a wet spell.

Avoid garden activities near plants in damp weather to minimize spore movement.

To Address Blackleg

Remove affected leaves and discard them in a sealed bag in the trash.

You may apply a foliar fungicide however, it may be of no use if the infection is extensive. In such a case, remove and discard all affected plant material.

Planting Broccoli, Cabbage, and Cauliflower

Broccoli, cabbage, and cauliflower are all members of the cabbage family. They are also referred to as cole crops. Cole crops are cool season vegetables which grow best at temperatures between 60 and 68ûF. When planted in the spring, these crops must produce good quality heads before the arrival of hot summer weather.

While the cole crops are cool season vegetables, they should not be planted when temperatures are consistently below 50 F. Broccoli and cauliflower plants exposed to prolonged periods (four or more days) of temperatures below 50 F may form heads prematurely. This premature head development is called buttoning. Buttoning occurs when plants are exposed to stressful conditions, such as prolonged periods of cold temperatures, dry conditions, and infertile soils. Also, large plants are more likely to button than young plants. Plants that button do not form usable heads.

In central Iowa, broccoli, cabbage, and cauliflower should be planted in mid-April. Start plants indoors 4 to 5 weeks before planting outdoors or purchase young, stocky transplants at your local garden center. Harden the transplants outdoors in a semi-protected location for a few days prior to planting.

The cole crops perform best in fertile, moist, well-drained soils. When planting these crops, space transplants 18 to 24 inches apart within the row. Rows should be approximately 24 to 30 inches apart. At transplanting, apply 1 pint of a starter fertilizer solution to each plant. A starter fertilizer solution can be prepared by placing 2 tablespoons of a complete analysis fertilizer, such as 10-10-10, in one gallon of water. Four to six weeks after transplanting, sprinkle 1 or 2 tablespoons of the complete fertilizer around each plant.

Broccoli, cabbage, and cauliflower require approximately 1 inch of water per week. Water the plants once a week during dry weather. Cultivate lightly around the cole crops as they have a shallow root system.

These crops can also be planted in mid-summer for a fall crop. Start the seed indoors in early to mid-July. Transplant the seedlings into the garden 4 to 5 weeks later.

Suggested broccoli, cabbage, and cauliflower varieties for Iowa include:


  • Green Comet, Packman, and Premium Crop

Cabbage, Green

  • Bravo, Dynamo, Gourmet, Heads Up, Rio Verde, and Stonehead

Cabbage, Red

  • Cardinal, Red Acre, and Regal Red

Cabbage, Savoy

  • Savoy Ace and Savoy King


  • Early Snowball, Fremont, Snowball 123, and Snow Crown

This article originally appeared in the March 21, 1997 issue, p. 24.

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