My Cactus Turned Black: Causes and How to Fix It

My Cactus Turned Black Causes and How to Fix It

If one of your cactus starts changing its color from green to black, do not feel bad, although the cactus plant now requires special attention to be healthy and green again. It is not unusual that one of these cactus plants turns black, but if you treat it properly, it will return to a healthy cactus again. In this article, we will discuss why our cactus turns black from green and how we can treat it so that it turns back to its original color.

Several factors can cause our cactus to change color from green to black, but the most well-known is improper watering, whether we water too much or too little. Other causes that cause the cactus to change color are bacterial and fungal diseases, pest infestation, low light conditions, and using too much fertilizer.

To know how to treat the situation of a black cactus or a cactus that begins to appear with black spots, you must dive deep into the cause of the color change.

Six common causes for your cactus turning black and how to fix it 

By understanding the causes and providing the appropriate care, you can fix your black cactus and restore it to its original healthy and green state. Remember to address the issue promptly and closely monitor your cactus’s progress as you implement the necessary fixes. Your cactus will return to its vibrant and beautiful form with proper care and attention.

Low Light Conditions

Low light conditions can cause your cactus to turn black, as these desert plants are adapted to thrive in environments with ample direct sunlight or bright light. When a cactus does not receive enough light, it can damage tissue and weaken the plant’s health. The lack of sufficient light can impede the plant’s ability to produce energy through photosynthesis, resulting in the darkening of areas of plant tissue. To prevent this issue, it’s essential to ensure that your cactus is placed in a location where it can receive adequate light exposure. Position the cactus near a sunny window or in a well-lit area outdoors. If natural light is limited, you can supplement it with artificial grow lights that mimic the intensity and spectrum of sunlight. By providing your cactus with the right amount of light, you can help it maintain healthy tissue and avoid the problem of blackened stems or discoloration.


Underwatering is the most common reason behind your cactus turning black, and it can harm the health of the entire plant. Cacti are desert plants adapted to thrive in arid conditions and require minimal watering. When they do not receive the proper care, their water reserves become depleted, leading to the darkening of their stems or the entire plant. Adopting a cautious approach when watering your cactus is the best way to prevent this issue. Allow the soil to dry out completely between waterings and ensure the pot has proper drainage to avoid waterlogged roots. By providing your cactus with the appropriate amount of water and following basic guidelines for its care, you can help maintain its vibrant and healthy appearance.


The cactus can turn black if there is too little or too much water
The cactus can turn black if there is too little or too much water

Overwatering is one of the leading causes behind your cactus turning black, and it can be detrimental to the health of your beloved plant. Cacti are adapted to survive in arid environments and are not accustomed to receiving too much water. When an overwatered cactus absorbs far more water than it needs, the excess water can lead to root rot and other issues that manifest as darkened or blackened stems. To prevent this problem, providing your cactus with the proper care is essential by allowing the soil to dry out thoroughly between waterings. Ensure the pot has excellent drainage to prevent water from accumulating around the roots. By carefully watering and providing your cactus with the right amount of water, you can help revive its health and restore its natural beauty.

Fungal & Bacterial Diseases

Bacterial and fungal diseases can be significant causes behind your cactus turning black, posing severe threats to its well-being. Bacterial necrosis and other bacterial infections can infiltrate the cactus’s tissues, leading to blackened areas on the stems and overall discoloration of the plant. Similarly, fungal infections can also contribute to the darkening of the cactus. These diseases often thrive in overly moist conditions or on wounded parts of the plant. Maintaining proper care and taking preventive measures to combat this issue is crucial. Avoid overwatering and ensure the cactus is placed in a well-ventilated area with adequate sunlight. If you notice signs of bacterial or fungal diseases, promptly remove the affected parts and quarantine the plant to prevent the spread of infection. Seeking professional advice and using appropriate fungicides or bactericides may also be necessary to save your cactus and restore its health.

Pest Infestation

Pest infestations can significantly cause your cactus to turn black, threatening the plant’s well-being. Certain pests, such as red spider mites, can target cacti and other plant species, feeding on their sap and causing damage to the delicate tissues. As these tiny pests multiply rapidly, they can weaken the cactus and lead to blackened stems or discoloration. To address this issue effectively, it is crucial to regularly inspect your cactus for signs of infestation, especially on the undersides of the leaves and along the stems. If red spider mites or other pests are found, immediate action should be taken to control their population. You can use appropriate insecticidal soaps or neem oil to combat these pests without harming the cactus. Ensuring a clean and pest-free environment for your cactus is essential to maintain its health and vibrant appearance.

Extreme Temperature Changes

As cacti are highly sensitive to abrupt fluctuations in temperature, extreme temperature changes can significantly cause they’re turning black. Cacti plants that are not accustomed to cold temperatures, especially freezing temperatures, can become damaged when exposed. When exposed to low temperatures, the plant’s tissues can be damaged, resulting in blackened stems or the entire plant. Sudden shifts from warm to cold weather can also harm the plant’s health. The best way to prevent this issue is to protect your cactus from extreme temperature swings. When it is cold, keep it indoors or provide it with adequate insulation. Avoid placing the cactus near drafts and cold windows in the winter. Maintaining a stable and suitable temperature for your cactus is essential to prevent blackened stems caused by extreme temperature changes.

Too Much Plant Food

As these hardy desert plants have unique nutritional requirements, too much plant food can result in your cactus turning black. As cacti thrive in low-nutrient environments, excessive fertilization can harm them. Cactus can accumulate salts and minerals in the potting soil when they receive a lot of plant food. This may result in blackening or darkening of the cactus’ stems. Choosing fertilizer specifically formulated for cacti and succulents is essential to fix this issue. If in doubt, err on the side of under-fertilizing rather than over-fertilizing, and follow the recommended dosage and frequency of fertilization. To prevent the problem of blackened stems caused by excessive plant food, you must give your cactus the right amount of nutrients.

Keep The Infected Plant Away From Others

One crucial step in dealing with a blackened cactus is to keep the infected plant away from others to prevent the spreading of any potential diseases or pests. Bacterial and fungal infections and certain pests can quickly transfer from one plant to another, especially if they are nearby. Quarantining the infected cactus will help contain the problem and protect your other cacti from being affected. Place the blackened cactus in isolation until you properly treat and resolve the issue. Additionally, thoroughly clean and disinfect any gardening tools that have come into contact with the infected plant to avoid inadvertently spreading the problem to healthy plants. This precaution can safeguard your cactus collection’s overall health and well-being and ensure a thriving and disease-free indoor plants garden.

final thoughts

In conclusion, if your cactus has turned black, it may initially be a cause for concern, but with the proper knowledge and prompt action, there is good news—many blackened cacti can be saved. Identifying the specific cause of the color change is the first step to implementing the correct fix. Whether it’s adjusting watering habits, providing adequate light, combating pests, or using appropriate fertilization, understanding the unique needs of different types of cacti, including indoor cacti, is essential. Remember to ask yourself: “What caused the blackening?” This will guide you in treating the issue effectively. If left untreated, blackened stems could indicate a rotting cactus, so inspect the plant’s tissue and take action accordingly. By practicing proper care and attentive maintenance, you can prevent blackened stems and ensure your adult plants’ long-lasting health and beauty, even those with black spines. With diligence and patience, you can revive your black cactus and enjoy its natural beauty once again as a testament to the resilience of these remarkable desert plants.


Hey, My name is Liat and I am addicted to house plants! I have at home more than 50 different types of plants of all kinds - succulents, cactus, tropical plants, orchids and more! Feel free to share the blog with friends on social networks.

Recent Posts