Common Cabbage Problems and How to Fix Them
Cabbage is one of the most rewarding crops in a vegetable garden, but it is also one of the most demanding. It needs steady moisture, enough space, cool temperatures and protection from pests. When one of those things is off, the plant usually shows it, either in the leaves, the head or both.
At our garden in Soshanguve, we have grown several cabbage crops and seen a range of problems. Some were caused by the weather, some by pests and some by watering habits. This article walks through the most common cabbage problems we have encountered, what causes them, and what we do to fix them.
If you want to see how we grew our cabbage crop from seedling to harvest, I covered that in how to grow cabbage from seedling to harvest.
In This Article
- Problem 1: Head browning and splitting
- Problem 2: Caterpillar damage on forming heads
- Problem 3: Cabbage aphids
- Problem 4: Inconsistent watering and split heads
- How feeding supports cabbage health
- What I learned from these problems
Problem 1: Head Browning and Splitting
One of the most common cabbage problems we have seen is browning and splitting on the developing head. The exposed central head turns dry and brown, the tissue starts to break down and in some cases the head splits open at the top.
This is usually caused by one of two things: sunscald or head splitting.
Sunscald happens when the head is exposed to direct sunlight for too long. Cabbage heads are normally protected by their outer wrapper leaves. If those leaves fold outward or the head pushes up, the tender inner leaves are exposed and can burn in strong afternoon sun.
Head splitting happens when the plant absorbs water too quickly after a dry spell. The sudden swelling of the internal tissue causes the head to crack open. This is common when watering is irregular, either from rain or from the gardener.
How to Fix Head Browning and Splitting
Both problems are easier to prevent than to fix. Once a head has split, it does not close back up. Once the exposed tissue has browned, that part of the head will not recover.
What we do:
- Water consistently. Deep watering once or twice a week is better than small daily splashes.
- Mulch around the base of the plant to keep soil moisture stable.
- Do not let the soil dry out completely between waterings.
- Reduce watering if heavy rain is expected.
- If the head looks exposed to strong afternoon sun, gently pull a couple of outer leaves over the top to shade it.
Problem 2: Caterpillar Damage on Forming Heads
Caterpillars are the most persistent pest we deal with on cabbage. They chew through the leaves, and once the head starts forming, they can tunnel directly into the tender inner leaves.
The damage pattern is easy to recognise. You see small to medium holes riddled through the outer wrapper leaves, and once you pull the head apart, the inner layers are also damaged. Sometimes you find the caterpillars themselves tucked into the folds of the head, or small green droppings around the holes.
The usual culprits are:
- Diamondback moth larvae
- Cabbage loopers
- Imported cabbageworms
These caterpillars are small and often the same colour as the leaves, which makes them difficult to spot until the damage is visible.
How to Fix Caterpillar Damage
Caterpillars need to be dealt with early, before they get into the head. Once they are inside the head, removing them is difficult and you usually lose part of the crop.
Our approach:
- Scout regularly. Check the undersides of leaves and the folds of forming heads at least twice a week.
- Hand-pick. Remove any caterpillars you find. Drop them into a bucket of soapy water.
- Apply Bacillus thuringiensis (Bt). This is a natural soil bacterium that targets caterpillars without harming beneficial insects. Spray it directly into the head and leaves during the late afternoon.
- Encourage predators. Birds, parasitic wasps and ground beetles all help keep caterpillar populations down.
- Rotate crops. Do not plant brassicas in the same bed season after season.
Gardening Lesson
Caterpillars are easiest to manage before the head forms. Once they tunnel inside, removal is slow and damage is high. Check the plants weekly, hand-pick what you can, and use Bt as a targeted organic control.
Problem 3: Cabbage Aphids
Cabbage aphids are small, grayish-green insects that cluster on the undersides of leaves and stems. They are covered in a powdery waxy secretion, which makes them look dusty rather than glossy.
The first sign of an aphid problem is usually a curled leaf. When you unfold it, you find a dense colony of tiny insects feeding on the sap. If the infestation is heavy, the leaves yellow, distort and dry out. The aphids also excrete a sticky substance called honeydew, which attracts ants and encourages sooty mold.
Aphids can also transmit plant viruses, which makes early management important.
We covered cabbage aphids in more depth in a separate guide, including identification, life cycle and management. You can read that here: cabbage aphid guide.
How to Manage Cabbage Aphids
- Physical removal: Tear off heavily infested leaves and squish the aphids inside. Dispose of them in the bin, not the compost.
- Water spray: A strong jet of water dislodges aphids from the plant. Repeat every few days.
- Soapy water spray: Mix one teaspoon of castile soap per litre of water. Spray on affected plants, especially the undersides of leaves.
- Companion planting: Garlic, onions and mint planted near brassicas help deter aphids.
- Encourage predators: Ladybugs, lacewings and parasitic wasps all feed on aphids.
- Neem oil: Apply as a spray to disrupt aphid feeding and reproduction.
Problem 4: Inconsistent Watering and Split Heads
Cabbage needs consistent moisture, especially once the head starts forming. Uneven watering is one of the most common causes of split heads and poor head quality.
The problem usually looks like this. The soil dries out for several days, then gets a heavy soak from rain or from the hose. The plant takes up water rapidly, the head swells faster than the outer leaves can stretch, and the head splits open.
The split itself is not the end of the crop. The cabbage is still edible, but the quality drops. Split heads do not store well, and the open crack is an entry point for rot and pests.
How to Prevent Split Heads
- Water deeply and steadily. Once or twice a week is better than a small splash every day.
- Check the soil before watering. Push a finger 5cm into the soil. If it is dry, water. If it is moist, wait.
- Mulch generously around the base of the plant. Mulch keeps soil moisture even.
- Harvest as soon as the head feels firm. Do not leave a mature head on the plant too long.
- If heavy rain is coming and the head is nearly ready, harvest it early rather than risk splitting.
How Feeding Supports Cabbage Health
Healthy cabbage plants resist pests and diseases much better than stressed ones. Feeding is one of the best ways to keep a cabbage crop strong through the season.
Our feeding system is built around two products working together. A slow-release fertilizer feeds the soil and the plant over the long term, while a liquid fertilizer gives a quick nitrogen boost when the plant needs it most, such as after transplanting or during early leaf growth.
For slow release, we use chicken feather fertilizer, which is rich in nitrogen and breaks down gradually over several months.
For the fast feed, we use a fish liquid fertilizer, diluted in water and applied every two weeks.
Both are the same fertilizers we make and use in our own garden. The liquid fertilizer is also available in our shop for anyone who wants to try the same feeding program.
A well-fed cabbage plant grows strongly, forms a tight head and recovers faster from pest damage. The feeding program alone will not stop caterpillars or aphids, but it makes the plant much more resilient when problems do appear.
What I Learned From These Problems
Cabbage is not a difficult crop, but it does not tolerate neglect. The problems we have seen came from things that were easy to fix once we understood what was happening.
The main lessons:
-
Consistent watering is non-negotiable.
Most cabbage head problems come down to moisture. Deep, steady watering prevents splitting and reduces stress on the plant. -
Scout for pests weekly.
Caterpillars and aphids build up quickly. Finding them early makes them much easier to manage. -
Shade the head if it is exposed.
A head that is not protected by its outer leaves can burn in strong afternoon sun. Gently folding a couple of leaves over the top is usually enough. -
Do not wait too long to harvest.
A mature head left on the plant too long is more likely to split. Harvest as soon as it feels firm. -
Feed for resilience, not just growth.
Combining slow-release and liquid fertilizers keeps cabbage strong through the season and helps it recover from pest pressure. -
Split heads are still usable.
Once a head splits, it will not close again. But it is still edible. Use it fresh rather than storing it.
Gardening Lesson
Cabbage problems are easier to prevent than to fix.
Steady watering, weekly pest scouting, steady feeding and a bit of shade for the head will keep most cabbage problems away. Once a problem shows up, act quickly, because cabbage does not recover slowly.
Soshanguve, Pretoria, South Africa
Growing Knowledge. Growing Food.