Why Cabbage Leaves Turn Purple And What To Do About It

Cabbage is a versatile vegetable that can be found in almost any garden plot. It’s easy to grow and yields well if you follow the cultivation guidelines.

However, it is possible that the leaves will turn blue or purple. This article will assist you in determining the causes of the problem and possible solutions.

Why Do Cabbage Leaves Turn Purple?

The usual white leaves with a greenish cast may turn blue or purple for the following reasons:

Deficiency in Nitrogen: While the color of the leaves will change, the growth of the cabbage will be slowed as well.

Early varieties are most vulnerable in spring when rainy weather reduces soil microflora activity. So, nitrogen is supplied sparingly to seedlings.

Deficiency in Phosphorus: Aside from the appearance of purple color, there is a decrease in leaf volume as well as slower development and formation of cabbage.

Transplanting seedlings into open ground causes stress to them. This short-term problem will go away in 7-10 days.

Temperature swings, frosts, and other extreme cold conditions. When seedlings are transplanted into soil that hasn’t been warmed to the necessary temperature 60-70°F (16-21°C), they will suffer from this problem.

Watering the soil insufficiently or excessively. Despite the fact that cabbage enjoys water, too much of it causes the leaves to turn brown, the root system to rot, and the plant to eventually die. 

When the soil is dry for an extended period of time, the leaves become stiff and blue.

Symptoms of the fungus blackleg, from which cabbage is completely unprotected throughout its life cycle. 

Root system damage by the fungus causes a halt in plant nutritional uptake, which affects the color of the leaves and ultimately causes death for the cabbage plant itself.

Clubroot Disease of Cabbage: This disease causes leaf wilting and leaves turning blue, which is most noticeable at midday. Knots form on the root system, preventing nutrients from being absorbed.

Bugs on Cabbage: Aphids and cabbage flies are the most common pests. In contrast to aphids, cabbage fly larvae burrow into the stems of the plant and eat the entire cabbage from the inside out.

It is the seedling preparation that determines both the quality and quantity of your cabbage. Before planting, be sure to acclimate the seedlings. Choose plants that are strong and healthy, and that don’t show any signs of fungus disease.

What to do if your cabbage’s leaves are purple?

A change in the color of the leaves from green to purple is usually a sign that it is time to take action to eliminate negative factors.

If the weather outside is pleasant and an external inspection reveals no signs of disease or insects, take the following steps to fix the purplish of the cabbage:

Add Fertilizer To Make Up For Deficient Phosphorus

You can use organic Fish Bone Meal fertilizer (Check the latest price on Amazon here) to make up for the lack of phosphorus in the soil. 

In addition to phosphorus, the mixture contains other ingredients necessary for assimilation. 

Expert gardeners also apply superphosphate (100 grams per bucket of water) and double superphosphate to their plots of land (50 g per 1 bucket of water). 

For best result mix decomposed manure or chicken manure with the fertilizer mix (3 kg per 1 sq. m.).

Adjusting Soil pH

The acidity of the soil has an impact on phosphorus absorption. The trace element’s absorption decreases with increasing acidity. 

Cabbage thrives in loamy soil with a pH of 6.2-7.5 (neutral or near-neutral).

If you want to lower the pH of your solution, try using limestone or dolomite powder, ash from wood or peat, or chalk.

If the cause of the purple color is a shortage of nitrogen, the problem can be rectified by applying decomposed humus (per 1 sq. m. 3-4 kg of raw materials).

Another option is to use a urea solution, you can make this up 30g per 10L of water.

In the event of heavy rain, the soil should not be allowed to become overly saturated. 

So the make sure to cover the garden beds with polyethylene film if possible. 

Lead furrows from the beds for water drainage, and loosen the soil 3-5 cm deep every day. 

If dry soil is the cause of the leaf color change, watering is increased by introducing 2-3 liters of water under each plant by drip watering technique.

Important! The purplish from the cabbage leaves will disappear within 10-14 days of applying the necessary nutrients and balancing the moisture content of the soil.

Protection Against Temperature Fluctuations

Although most cabbage varieties are cold-tolerant, sudden temperature changes cause the leaves to turn purple.

The following measures are taken to prevent color changes and deterioration of taste:

• If it’s cold outside (like -10°C), a thick layer of straw insulates the beds, keeping them safe from snow and hail.
• Add mulch or straw to the soil as a way of protecting it from erosion.
• Wait for the temperature to rise; the purple color will fade on its own.

Disease and Pest Prevention

If diseases or pests have caused the cabbage leaves to turn purple, try these methods to save the plant: 

Cabbage Black Rot

In order to avoid planting diseased seedlings, examine each one for symptoms of disease and discard the diseased one. 

Follow the same procedure with mature cabbage plants in order to prevent the further spread of the disease.

When there is a minor infestation, treat the soil with a weak manganese solution-1 liter per bush.  Apply a copper-based fungicide to control heavy infestations. 

If the disease still progresses, uproot the infected plants are and disinfect the soil with a 1% solution of manganese solution or copper sulfate.

Preventive measures also include the use of a calcium nitrate solution or lime milk (1 tbsp of lime per 10 liters of water). 

In order to avoid black rot disease, you must plant cabbage with a certain spacing between plants and between rows: 70 cm between plants and 80 cm between rows.

Clubroot of Cabbage

When a plant becomes infected with a disease, make sure to remove and burn it. 

Then replace them with plants are planted that are not susceptible to this disease, because the disease-causing agents can survive in the soil for up to 7 years. 

As a preventative measure, pour 3 tablespoons of ash or 1 tablespoon of calcium nitrate into the planting hole. Using a measuring cup, add the additives to 1.5 liters of water.

If this indicator is higher than normal, lime the soil (200 g per 1 sq. m.) causes scab to appear because of increased soil acidity.

Cabbage Fly

There are no effective insecticides to combat a cabbage fly invasion. But a monthly treatment of black pepper and dry mustard powder (1:1) on cabbage worked wonders for me.

Aphids on Cabbage

Aphids are eliminated with neem oil or natural predators like ladybugs, parasitic wasps. To prevent it, you can use powdering with ashes or spraying garlic mixture (400g garlic heads boiled for 2 hours in 10 liters of water) or citrus peel infusion (1 kg per 10 liters).

How To Avoid The Purple Leaf Problem In Cabbage

Follow these simple rules to grow cabbage without getting into trouble:

• Use varieties are selected based on the climate conditions of the area;
• Before planting the seeds, let them soak in a weak solution of manganese.
• Make sure to slowly acclimtize the seedlings are hardened off before going into the open ground. 
• Cabbgae thrives in soils that have a pH between 6.5 and 7.5, so check the pH and make adjustments if necessary.
• Follow crop rotation rules, such as not planting cabbage immediately after plants that share diseases (such as radish, radish);
• Choose well-lit locations for planting and keep plants 70 cm apart from each other and rows 80 cm apart.
• Avoid overwatering and over-drying the soil.
• Preventative measures against disease and pest infestation, such as fertilizer application on schedule, are critical to overall healthy gorwth of your cabbage.