Why is My Cactus Turning Red? [How to Fix]

Cactus plants are very resilient but also have their limits when it comes to environmental changes. For example, they love basking in indirect sunlight but providing too much sunlight could be detrimental to their health. Cacti may turn red to indicate that they are receiving too much light.

Cacti also turn red in response to dramatic changes in the surrounding environment, such as temperature swings and exposure to diseases.

Let’s look at some of the primary causes why your cactus in California may turn red.

CausesQuick Solutions
Lack of waterUse the finger test to check the soil’s moisture levels and water the plant accordingly.
Excessive SunlightBring the plant indoors if it was placed outside
Magnesium deficiencyUse magnesium sulfate fertilizers to remedy the problem
Temperature fluctuationsDon’t place the plant near a heat source
Root healthClear the damaged roots and keep the plant healthy to encourage the growth of a new root system
PathogensUse a herbicide to see if it clears the pathogen. If not, discard the affected foliage to prevent the pathogens from spreading.

Lack of Water

Underwatering can also cause the leaves to turn a shade of red. This is a common theme across most succulents. The cactus’s shape can also change, becoming smaller and more wrinkled with time.

Cacti are believed to change their color during a drought to reduce photosynthesis, so they may lose less water. This will reduce the amount of chlorophyll in the plant, causing the color to lean more toward red and brown.

You can tell that the plant is underwatered if the cactus, in addition to changing color, also changes its shape. It’s time to water your cactus.

Just because they’re classified as drought-tolerant doesn’t mean they can survive without water. Most experts agree that you should water your cactus once every month.

In addition, you can check the soil for its moisture level if the plant is growing on the soil. Insert your finger 2 inches into the soil and try to feel the moisture levels. If the soil feels dry, it’s time to water the plant. And if the soil feels wet, the cactus does not need more water.

Obviously, your cactus will need more frequent watering sessions if placed near a sunny window in the summer months. Allow the water to seep into the soil to help the plant absorb moisture.

Pro tip: Always make sure that the point has plenty of drainage holes so that any excess water can be drained out. Overwatering can have devastating consequences on your plant’s health and will lead to root rot.

Excessive Sunlight

Cactus plants use a special pigmented substance called anthocyanin to protect them from various environmental stressors, such as excessive sunlight.

If the plant is exposed to too much sunlight, it will release red anthocyanins to lower the levels of green chlorophyll. This will minimize the number of cells destroyed by UV radiation.

This problem most commonly occurs in the spring months. By contrast, sunny days in the winter months are shorter. The cactus has built-in mechanisms to adapt to these environmental changes. It changes into the red to reduce the damage in the spring months.

The plant may also do this when you move it from an indoor environment to an outdoor one or from an east-facing window to a south-facing one.

Note that most cacti species require nearly 6 to 8 hours of sunlight. This is why placing them in a south-facing window is a good idea. You may gradually increase sunlight exposure to help your plant adapt without turning a shade of red.

Magnesium Deficiency

Magnesium plays an important role in the development of cacti. Providing cacti with a balanced diet of nitrogen, potassium, phosphorus, and magnesium is important. Without these nutrients in place, the plant’s photosynthesis process will fail to keep up, and it will change a shade of red.

In the wild, cacti usually receive an abundant amount of magnesium from the soil or water. However, this may not be commonplace indoors, especially if your soil doesn’t contain magnesium sulfate.

The best way to alleviate this problem is to feed it magnesium fertilizer. You may also use a compound fertilizer that contains all the nutrients, including magnesium. The best time to feed your cacti is in the early spring, just before the plant grows. But if you notice a color

change, you may intervene and feed it some magnesium sulfate to help with recovery.

Temperature Fluctuations

Sudden fluctuations in temperature can also cause the cactus to turn a shade of red. As mentioned, the cacti will release anthocyanins to prevent their cells from getting damaged.

You may expose your cacti to temperature fluctuations if you take them outdoors in the summer. Come nighttime; the temperature will dramatically decrease, causing the cactus to change its color. Even if your cactus is accustomed to growing outdoors, it will change its color if exposed to a cold spell or, worse, frost.

Placing the cacti near a heat source, such as an HVAC or air conditioner, can also cause a similar change. For this reason, you should isolate your plant from heaters.

Keep your cacti within a temperature range of 10°C to 30°C. Going too far above or below this temperature range will cause stress to the plant.

Root Health

Root rot is a common reason for cacti to turn red. In the case of root rot, the cacti will also shrivel up and give off a foul odor at the base. Overwatering often leads to root rot. Other reasons for foot rot include temperature fluctuations and lack of sunlight.

The good news is that cacti can survive without roots because their leaves store a large amount of water. They may even grow a new root system if you treat them early.

If overwatering is the cause of root rot, you will have to stop watering the plant. The next step is to quarantine the cactus by removing it from the pot and purging the soil of rotten organic material. Make sure to use a sterile tool to clear away the rotten roots. Try not to damage any healthy foliage.

Treat the plant with a fungicide and place it in well-drained soil. Make sure the pot has lots of drainage holes. Don’t water the cactus for several weeks. You may resume watering at regular intervals. You know you’re on the right track if the cactus starts to recover.


Cacti can get infested if placed in contaminated soil or grown from an infected houseplant. A Cactus cyst is a common infection that may affect the roots. Besides causing the plant to turn red, cactus cysts can cause a number of symptoms, such as wilting and stunted growth. An obvious sign of pathogens is the presence of pearl-like growth on the roots.

It is relatively difficult to treat cactus cysts, so prevention is better than cure. Make sure to keep the plant in a sterilized pot and elevate it from the floor to minimize contact with the soil.

In the case of an infestation, it may be better to discard the affected foliage to prevent the disease from infecting other houseplants.

Note: Red Spines isn’t a Bad Sign

You may notice the growth of red spines on your cactus and fear that the plant is damaged. In reality, the growth of red spines is a natural part of their growth cycle. The presence of red spines does not require intervention and is completely natural. In most cases, the cactus spine will return to its original color after some time.

Red spines also indicate that your cacti have entered a new stage of growth and that your plants are doing well.

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Wrapping Up

So, there you have it, six common reasons why your cactus in California may be turning red. But you should pay attention to not just the color of the foliage but also its shape. For example, wrinkled foliage indicates a lack of water and shriveling shows that the plant may suffer from root rot.

Finally, it may not all be bad if your cactus spines change a red shade. This usually means that the plant has entered a new stage of growth. Let us know how you treated your cactus plants that turned red.

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