5 Reasons Why Your Brussel Sprouts Won’t Grow Tall

You’ve spent a great deal of time planting and taking care of your Brussels sprouts. After a while, however, you notice that your plants are stunted and no longer growing as expected. So why aren’t your Brussels sprouts growing tall?

Your Brussels sprouts are not growing tall due to one of the following reasons:

  1. Cabbage aphids
  2. Club root disease
  3. Wirestem fungus
  4. Root cyst nematodes
  5. Low soil acidity.

This article will first examine the right conditions to grow Brussels sprouts. I’ll then delve deeper into each of the reasons why your Brussels sprouts are not growing tall. Let’s get started! 

The Ideal Conditions for a Brussels Sprout Plant

Growing Brussels sprouts can be challenging since they require specific conditions to thrive. As cool weather plants, Brussels sprouts need to be harvested in the fall or even early winter, depending on the outside temperatures. 

While they need full sunshine, Brussels sprouts cannot be in an area where temperatures exceed 80 °F (27 °C), making it tricky to know where to plant them in your garden. If the environment you live in is warmer, it is best to grow them in a partially shaded area.

Brussels sprouts typically take 3-6 months to fully mature and grow from 2-3 feet (61-91 cm) tall, depending on the variety. That is the time frame you will want to follow if you notice that your plants seem to have stopped growing or are having a challenging time getting to that height.

Why Your Brussels Sprouts Won’t Grow Tall

Below are some reasons why your once healthy Brussels sprouts no longer seem to be growing:

1. Cabbage Aphids

Cabbage aphids are one of the first culprits you will want to look into if your Brussels sprouts seem to have stopped growing in height. These pests typically attack young Brussels sprouts, stopping their growth before it even has a chance to start. 

Severe infestations of cabbage aphids have the ability to prevent entire crops of vegetables from growing to their full capacity, and they tend to specifically target plants like Brussels sprouts that are members of the cole family. 

Unfortunately, out of all the reasons for stunted growth, cabbage aphids are the most difficult to discern. They are very small and burrow within the leaves of the sprouts, which then curl around, making them hard to spot.  

The fact that they can hide within the Brussels sprouts’ leaves also makes it challenging for their natural predators to find them. If they were easy to spot, they could be mostly taken care of by the insects that feed on them.

The best way to prevent cabbage aphids from returning for future harvests is to control the weeds in your Brussels sprout plot. If there is a lack of extra weeds for them to eat from, the population will be a lot easier to keep under control. 

2. Club Root Disease

Another potential reason your Brussels sprouts may not grow to their full height is an infection called club root. 

This disease affects the roots of your Brussels sprouts and happens mostly underneath the soil, which makes it difficult to spot if you do not know what you should be looking for. 

Club root comes from a fungus that causes the bases of fruits and vegetables to grow swollen and deformed. The roots cannot take in the energy they need to mature properly, and the growth of the plant is stunted. 

Sadly, a way to kill off the fungus that causes club root disease has not been discovered yet. That fact is also problematic since the fungus can live in the same plot of soil for many years, affecting future crops. 

You will want to be sure that you are not planting your sprouts in an area that had other plants in the cole family growing there recently. Planting fruits and vegetables of the same family in the same area repeatedly heightens the risk of funguses attacking them. 

The best way to keep club root from having an adverse effect on your Brussels sprouts’ growth is to plant your crop in a new section of the garden every few years. 

3. Wirestem Fungus

A different fungus that could harm the growth of your Brussels sprouts is wirestem. This disease typically targets young seedlings when they are first put into the ground, but it does also have the potential to stunt more developed plants.

As the name states, wirestem fungus hits the growing stem of Brussels sprouts the hardest. When wirestem reaches brand-new seedlings, it affects the sturdiness of their limbs, causing the plants to become top heavy, fall over, and die on the ground. 

Older plants that catch the disease typically start to crack, with lesions developing on their stems. The plant’s growth then becomes stunted before it starts to wilt. As the disease continues to progress, the plant will stop growing and start to die slowly. 

Like club root disease, there is no cure for the wirestem fungus. The primary way to prevent the infection from festering is to avoid overwatering your Brussels sprouts while they are young. 

Wet soil is a perfect breeding ground for fungus and mold, and wirestem will have a much easier time reaching immature Brussels sprouts at the beginning of the growth process if they are consistently sitting in too much moisture. 

4. Root Cyst Nematodes

Another species of pest that can keep your Brussels sprouts from growing tall is root cyst nematodes. 

These parasites dig deep into the roots of the vegetables and create a cyst pocket that can quickly become a breeding ground for nematodes if not caught soon enough. The leaves on your Brussels sprouts will start to turn yellow, and their growth will be stunted as the infestation takes over. 

When root cyst nematodes start to appear, the best action is to rotate your Brussels sprout crops to a new area of the garden. These pests can stay in the soil for several years after an infestation happens, so planting your next crop of sprouts in a different section of land will keep the issue from repeating itself.

Another method you can try is soil solarization. This process involves covering the infected soil with clear plastic or another material that allows the sun’s heat to shine through and trapping the warmth to kill any bacteria, fungus, or pests. 

If you attempt this technique, be sure to do it during the middle of the summer when the sun is at its strongest, as it will have the most potent effect on the parasites. 

5. Low Soil Acidity

The final potential reason your Brussels sprouts will not grow tall is that the soil they are planted in does not have the proper pH balance and is too low in acidity. 

Generally, soil pH should be between 6.0 and 7.5 for most fruits and vegetables to grow properly. If it is below this range, the roots of your plants will not be able to absorb the nutrients they need to grow, and they will end up being stunted. 

Thankfully, readjusting soil acidity levels is a relatively straightforward process that can be fixed in a timely manner. All you need to do is adjust the pH of the soil with lime. 

A thin layer of lime over the top of your crops will help a lot, but you can also work the lime into the top 6 inches (15 cm) of the soil where your plants are growing.

You can monitor the pH levels over the next 2-3 months, and as long as they stay within the healthy range, your next harvest of Brussels sprouts should grow nice and tall. 

Final Thoughts

While several of the potential reasons your Brussels sprouts aren’t growing tall do not have complete fixes, there are ways to prevent the issues from occurring in the future.

As long as you keep an eye on your plants and pay attention to any warning signs of potential problems, your Brussels sprouts will grow tall every time.

Alexander Picot

Alexander Picot is the founder of TheGrowingLeaf.com and its lead content writer. He created the website in 2022 as a resource for horticulture lovers and beginners alike, compiling all the gardening tips he discovered over the years. Alex has a passion for caring for plants, turning backyards into feel-good places, and sharing his knowledge with the rest of the world.

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