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Top Common Problems Growing Brussels Sprouts and How to Fix It

Brussels sprouts are a fall crop that prefers cool weather. You might find them in the grocery stores in the summer, but if you want to grow them at home, you’ll need to wait until the fall or very early spring to do so. They’re an easy plant to grow, but just like any other plant, they have their share of pests and diseases you’ll need to combat.

The top common problems you might have when growing brussels sprouts are easy to fix. The biggest issue is typically cabbage worms or other insects. Other problems are diseases or lack of plant growth. All of these problems can be prevented by proper care or fixed organically.

Let’s take a look at common problems and how to solve or prevent them. Growing brussels sprouts isn’t difficult; you just need to know how to do it properly.

How to Grow and Care for Brussels Sprouts

Most problems your brussels sprout plant might face can be prevented if they’re taken care of correctly. Following all the guidelines to a tee won’t make your plant spotless, but a healthy plant has a better chance of enduring pests and diseases than an unhealthy plant does. Let’s get into how to properly care for Brassica oleracea

When to Plant

  • Thrives in temperatures of 59 – 64°F (15 – 18°C)
  • Takes anywhere from 90 – 180 days to harvest
  • Becomes sweeter in cold weather

Brussels sprouts are a cool-weather crop. They thrive in cooler temperatures and can’t grow as well in warm weather. You can grow them in early spring or in the fall. 

If you live in an area that has especially hot summers, planting in the fall would be the better option. Cool weather causes the plant’s food reserves to turn into sugar, causes the sprouts to taste sweeter. If spring in your area reaches above 64°F (18°C) and the summer will be hotter, you risk growing bland or bitter sprouts.

It might take as little as three months to get your first harvest of brussels sprouts. Sometimes, it can take up to 6 months for all of the sprouts to mature. Take this into consideration when you’re deciding the proper time of year to plant your brussels sprouts.

Spacing Is Key

Many diseases and pests can be avoided if you space the plants properly. When brussels sprouts are crammed too closely together, it’s easier for diseases to spread and for pests like cabbage worms to travel from plant to plant. Spacing must be considered from the very beginning, even if you start the seedlings indoors.

Sowing Directly in the Garden

The best time to sow the seeds directly in the garden is in the fall, about four months before the first frost. Or, you can sow them in the spring 2 or 3 weeks before the last frost.

Plant 2-3 seeds together in the same hole. Each hole should be about 24 in. (60 cm.) apart from each other in each row. The rows themselves should be about 30 in. (76 cm.) apart. The plants grow about 2 ft. (60 cm.) tall, and the leaves stretch out pretty far, so you need to have plenty of room between them.

Once the plants have sprouted, thin them out so there is only one plant in a hole so the plants won’t be overcrowded.

Sowing Indoors

If you want to start them indoors, follow the same guidelines as above by planting 2-3 seeds together. You will also need to thin these out, so only one plant is in a container.

It’s best to plant the seeds in biodegradable containers so you can plant the entire container in the ground and not have to disturb the roots. You will have to plant the containers a little deeper to keep them steady.

Proper Water and Sunlight

Brussels sprouts need moist soil and at least 6 hours of sunlight per day. Moist soil can be tricky to gauge. Waterlogging the plants is a common mistake when you’re trying to keep the soil moist.

If you can form the soil into a ball, that’s how you know the soil is moist. If water drips from it, you probably have too much water. If the soil doesn’t stick together, it’s definitely time to water it again, but you shouldn’t wait until it dries out to water them.


Brussels sprouts require a lot of nutrients to grow. You might need to amend your soil before planting or provide fertilizer. The plants tend to have a deficiency in boron, which may result in tough browning leaves. Adding borax to the soil will help correct this.

If you use organic matter like compost, you won’t have to use as much fertilizer. Be sure to provide plenty of nutrients to your plants while it grows.


The little sprouts are ready to harvest when they are 1 – 2 in. (2.5 – 5 cm.) in diameter. You can remove the big leaves as you go, or you can remove them all at once. By doing so, you will speed up the maturing process and will be able to harvest the sprouts a little sooner. The sprouts on the bottom will be the first to mature, and then you can move up.

Keeping a plant healthy will prevent problems or will allow the plant to recover from pests and diseases. Unfortunately, a perfectly cared for plant is still not immune to the problems that hit brussels sprouts.

Bacterial Diseases

Bacterial diseases are usually found in moist areas. You can avoid these diseases by using watering methods like drip irrigation or by watering at the base of the plants. Watering overhead can cause bacterial growth on the leaves. If the plants are planted too closely together, the diseases can easily spread from leaf to leaf. 

Bacterial Leaf Spot

This disease looks like black or purple spots on the outside leaves of the plant. The spots usually have yellow circles around them.

To avoid this disease, don’t use overhead watering. If a plant is diseased, dispose of it so it can’t infect other plants. If the infection gets out of control, don’t plant brussels sprouts next year so the infection can die off.

Black Rot

Black rot doesn’t look black on the outside. Instead, it looks like a brown and yellow V shape. The inside of it is black, which is what gives it the name.

This disease spreads through water, so you should avoid overhead watering even if you don’t see signs of the infection. An infected plant can also spread the bacteria by its seeds, so you need to remove the plant before it goes to seed. 

Avoid planting in the infected area in the next season, as the disease can live on other crops like turnips, radishes, and other cole vegetables. 

Cabbage Worms

Cabbage worms are the caterpillars of 4 different kinds of butterflies or moths: small white, cabbage looper, cabbage webworm, and the diamondback moth. The caterpillars are typically thick and green and can be found on cole vegetables, including brussels sprouts.

The butterflies will lay their eggs on the underside of the leaves. They’re white but turn yellow as they mature. Once the caterpillar emerges from the egg, it continuously eats until it goes into its cocoon. 

Birds, paper wasps, and yellow jackets are all natural predators to the cabbage worm. Chickens and ducks also like to eat them. If you let these critters hang around your garden, they might be able to help lower the cabbage worm population for you.

You can also handpick the worms off of the brussels sprouts, but it’s possible you might miss some if this is your only method of control. Try covering the plants with a row cover to keep moths and butterflies away from your crops, so they don’t have a chance to lay eggs.

Another option is to use intercropping to your advantage. Cole crops with red leaves aren’t as desirable to butterflies, and aromatic herbs like sage or oregano might repel butterflies. Plant these plants around your brussels sprouts, and you might see fewer cabbage worms.

Falling Over

Brussels sprouts grow fairly tall, which means they might fall over. The main reason they fall over is that they weren’t planted deep enough in the first place. Whether you sowed the seeds directly or transplanted seedlings into the garden, you need to make sure the roots are fully covered and are anchoring the plant.

You can build the soil up around the stalk of the plant as it grows to encourage steady anchoring. Build the dirt up about 6 in. (15 cm.) by late summer, and it should be sturdy for the rest of the growing season. If this doesn’t help, you will need to stake the plant to help support it.

Look in seed catalogs for shorter brussels sprout plants. There are a few varieties that don’t grow as tall and are less susceptible to falling over. 

Flowering Too Soon

Bolting is when the brussels sprout plant grows a flower to form seeds. Once the plant does this, it will no longer grow sprouts or the head of leaves at the top of this plant. Bolting means that the plant is coming to the end of its life – it makes seeds so the plant will continue to live on.

Sometimes, this bolting process happens far too soon. It’s usually because the temperatures are too cold. Even though the plant is a cool-weather crop and can handle some light frost, extended cold temperatures will signal to the plant that its growing season is over, and it needs to produce flowers.

Ideal temperatures for a brussels sprout plant is above 59°F (15°C). Prolonged exposure to temperatures below 50°F (10°C) will cause the plant to bolt.

Fungal Diseases

Much like bacterial diseases, fungal diseases grow in moist areas. The most common diseases are powdery mildew and downy mildew.

Powdery mildew looks like a white powder. You need to get rid of the environment that allowed the fungus to grow in the first place. Full sun exposure, that’s at least 6 hours of sun, and watering at the base of the plant will prevent it from growing. Remove unnecessary foliage to create more airflow around the plant. The mildew thrives in humid areas. Airflow and bright sun don’t allow humidity to stick around. 

Downy mildew functions the same way as powdery mildew, but this one is yellow and contains patches of grey. Keep plenty of room between the plants and don’t water at night to prevent both downy and powdery mildews away from your plants.

These two diseases infect more than just cole vegetables. Your entire garden can be susceptible to them, so keep a close eye on all of your plants. If the mildews begin to spread, try removing the infected plants or thinning them out, so the leaves don’t touch each other.

Not Many Sprouts

The number of leaves your plant has will determine how many sprouts it grows. This is why it’s so important to make sure your plant has the proper conditions from the very beginning. Inadequate water, sunlight, soil fertility, or temperatures can all contribute to the plant not producing many leaves.

The earlier you plant the seeds, the better. If you want the plant to be a fall crop, you’ll need to plant in late summer or early fall when the temperatures are closer to the ideal maximum temperature of 64°F (18°C). Be sure to use fertile soil. Add some compost or other nutritional supplements to the soil to make sure the plant will have enough for the entire growing period.

This problem isn’t easily fixed once it makes itself evident. Prevention is really the only method you can use to save the plant from not producing enough sprouts.

Sprouts Don’t Taste Good

Brussels sprouts taste the sweetest when they’re harvested in the cool temperatures of late fall. If you harvest them in the middle of fall, they might seem to taste bland. Try to wait until the temperatures are a bit cooler before you harvest so you can eat them at their best flavor.

Brussel sprouts can be a bitter vegetable, but most, if not all, modern varieties have been bred in such a way that they’re not bitter like they used to be. If your sprouts taste bitter, it’s natural, and the level of bitterness will depend on which variety you grew. Some modern varieties will still be bitter, but it shouldn’t be so bad that you can’t eat it. If you don’t like the bitterness at all, try to wait until the “sweet spot” in late fall to harvest the sprouts for a sweeter flavor.

Viral Diseases

Brussels sprouts can also be infected by viral diseases. Many viral diseases are most common in temperate areas and are transmitted through aphids and other insects. The viruses that affect brussels sprouts can also infect the other cole vegetables.

Turnip Mosaic Virus

This disease was once called the cabbage black ringspot virus and can infect any of the cole vegetables as well as a few other plants outside of the family. The virus is hosted in weeds and is transferred by aphids that go from plant to plant.

The virus will affect the leaves of the brussels sprout plant and develop yellow or brown rings. Sometimes these rings will come in the form of patches instead.

Since aphids are the culprits that spread this virus, you will need to kill off all the aphids and prevent them from getting near your crops.

Cauliflower Mosaic Virus

This virus also infects cole vegetables but can’t infect vegetables outside of the brassica family. It’s normally found in temperate regions around the world. Aphids are once again the culprits of spreading the virus. They pick it up from infected crops or weeds and bring it to cole crops.

This virus is hard to notice at first. You won’t realize a plant is infected until later in the season when the brussels sprouts are stunted and are low quality. A discolored mosaic pattern will appear, and the veins will stand out from the rest of the plant.

Keeping aphids away from your brussels sprouts is the only way you can prevent this and other viruses. Grow your plants under a mesh or screen covering to prevent aphids from getting inside. Insecticides are a way to get rid of them, but if you prefer a more organic approach, covering them will be the easiest preventative measure.

Final Thoughts

These are the most common problems that affect brussels sprout plants. While it may seem like a lot to handle, you might not experience any of them if you take preventative measures in the beginning. Make sure you’re supplying enough sunlight, water, and nutrients from the moment you plant the seeds or transplant the seedlings into your garden. If your healthy plant does end up with a pest or disease, it will be able to come back from it much easier than a sick plant can.

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