Cabbage leaves turning purple is a pretty common issue that gardeners face.
In most scenarios, the leaves will turn purple due to a lack of key nutrients like phosphorus and nitrogen. They may also turn purple due to overwatering, underwatering, or pests and diseases.
In this guide, we’ll explore seven reasons why your cabbage leaves are turning purple, what you can do about it, and tips for preventing it from happening again.
- A Quick Note – Some Types Of Cabbage Are Purple
- 7 Common Cabbage Leaves Turning Purple
- Preventing Cabbage Leaves From Turning Purple
- Tips for Healthy Cabbages
- In Summary
A Quick Note – Some Types Of Cabbage Are Purple
Certain types of cabbage (like January King, for example) grow purple leaves naturally, so before you assume something is wrong with your cabbage, make sure you don’t have one of these varieties.
7 Common Cabbage Leaves Turning Purple
Now that you’ve double-checked whether your cabbage should naturally produce purple leaves, let’s get straight into the list.
1. Lack Of Phosphorus
One of the main reasons your cabbage leaves might turn purple is the soil’s lack of phosphorus.
Phosphorus is an essential nutrient for plant growth and is responsible for root development, blooming, and fruiting.
A deficiency can lead to purple or reddish-purple leaves, particularly around the veins.
To combat this, you can add phosphorus-rich fertilizer to your soil to help balance the nutrient content.
Luckily, all complete fertilizers you can find in various stores contain phosphorus.
Ensuring your soil has the proper pH can also aid in phosphorus uptake (more on this later).
2. Nitrogen Deficiency
Another possible cause for purple cabbage leaves is nitrogen deficiency.
Nitrogen is crucial for leaf development and coloring specifically, insufficient levels can result in stunted growth and purple leaves.
To remedy this, you can apply a nitrogen-rich fertilizer. Complete fertilizers also contain nitrogen, so this can be tackled with one fertilizer.
3. Temperature Fluctuations
Temperature fluctuations, particularly in cold weather, can cause cabbage leaves to turn purple. It’s very common for cabbage leaves to turn purple over the winter.
This is because cold temperatures can hinder the plant’s ability to photosynthesize.
To help prevent this issue, plant your cabbage appropriately for your region, use row covers to protect them from frost, and maintain a consistent temperature throughout the growing season.
Overwatering your cabbage can also lead to purple leaves.
Excessive moisture in the soil effectively suffocates the roots, making it difficult for them to take up nutrients and therefore affecting the leaves.
If the soil is overwatered for prolonged periods of time, it can also lead to root rot.
To avoid this issue, monitor your soil moisture levels and only water the plants when the soil feels dry.
Underwatering can also cause your cabbage leaves to turn purple. Insufficient moisture in the soil can stress the plants, hinder nutrient uptake, and lead to purple leaves.
To prevent this, regularly check your soil for dryness and water your plants as needed.
6. Diseases and Pests
Diseases and pests can cause various symptoms in your cabbage plants, including purple leaves due to the damage they can cause to the leaves and the plant’s overall health.
Cabbages are prone to many diseases, from downy mildew to black rot to leaf spot.
They can also be infested with pests that feed on the leaves, like loopers, moths, and cabbageworm.
To protect your cabbage from fungal infections and pest infestations, use proper crop rotation, remove infected plants, and use disease/pest-resistant cultivars when possible.
7. Soil pH
If your soil pH is outside the ideal range for cabbages, it will affect nutrient uptake.
As nutrients like phosphorus and nitrogen are vital for leaf and root growth and development, an incorrect soil pH can quickly cause leaves to turn purple.
To combat this issue, keep the soil pH around 6 to 7.
Preventing Cabbage Leaves From Turning Purple
It’s a lot easier to keep the leaves green and healthy in the first place – here are some easy tips to achieve just that.
Soil Preparation and Testing
To prevent your cabbage leaves from turning purple, start by preparing your garden’s soil.
Test the soil to ensure it has the right pH level, as cabbage plants require slightly acidic to neutral soil with a pH between 6 and 7.
Add organic matter, such as compost or well-rotted manure, to create a rich, loamy soil that provides essential nutrients like potassium, phosphorus, and magnesium for the healthy growth of your cabbages.
Proper Watering Techniques
Water is crucial for the growth of your cabbages.
The secret is maintaining consistent soil moisture to prevent drought stress that can lead to purple leaves while avoiding overwatering.
To do this, water infrequently with around 1 to 2 inches per week.
Cabbage plants thrive in moderate temperatures between 60-65°F (15-18°C).
Protect your plants from severe temperature fluctuations that can cause stress and purple leaves.
Use row covers or frost blankets during colder nights in spring, and provide shade during hot summer days to prevent scorching.
To provide the nutrients your cabbage plants need, use a balanced or complete fertilizer (10-10-10) with nitrogen, phosphorus, and potassium.
You’ll only need to fertilize once or twice monthly, but it can greatly affect the leaf quality.
Disease and Pest Control
Monitor your cabbages for signs of diseases and pests that can cause leaves to turn purple, such as downy mildew or white mold.
Practice good garden hygiene by removing crop debris and infected plants.
Keep the proper spacing between plants to improve airflow and prevent diseases from spreading.
Tips for Healthy Cabbages
Cabbages have a lot of other care requirements aside from those that focus on fixing issues with purple leaves.
Here are some important tips for growing healthy cabbages.
Proper Spacing and Airflow
To maintain healthy cabbage plants in your garden, it’s important to provide proper spacing and airflow.
When transplanting cabbage seedlings, space them about 12-20 inches apart,, depending on the variety.
This allows for adequate room for growth, as well as preventing the spread of diseases between plants.
Good airflow also discourages pests and keeps the leaves dry, reducing the chances of fungal infections.
Remember to thin out any overcrowded areas as your cabbage plants grow.
Using Organic Compost and Mulch
Incorporate organic compost into your soil before planting cabbage.
This will add valuable nutrients to the soil and improve its structure, promoting healthy root growth.
Organic compost is a favorite among master gardeners because it supports productive crops and healthy vegetables.
In addition to compost, consider using a layer of mulch around your cabbage plants, particularly in the fall and winter months.
Mulch helps to regulate soil temperature, retain moisture, and suppress weeds.
For best results, use an organic mulch material, such as straw or shredded leaves.
Monitoring Soil Nutrient Levels
It’s important to provide lots of nutrients like nitrogen and phosphorus to keep your cabbage plants in top shape.
Organic compost and complete fertilizers are your best friend here. Keep your soil full of compost to boost the nutrient content and fertilizer once or twice monthly to enhance this.
If your cabbage leaves are turning purple, there’s a strong chance that it’s due to a nutrient deficiency – usually nitrogen or phosphorus.
By implementing a fertilizing routine, your cabbage leaves should bounce back to health in no time. Pruning affected leaves is a good idea to help concentrate the new growth on existing leaves that are green.
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