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Cactus Turning Red: Why And What To Do?

Succulents are heat-loving plants and they are very sensitive to environmental changes. An indicator is their appearance, they can change color or shape. Cacti are no exception in this respect.

The main reason why a cactus turning red is due to excessive sunlight. The second reason why cactus leaves turn red is insufficient watering. Also, the cactus turning red due to too drastic temperature changes.

Besides, the cactus can turn reddish if there is a lack of magnesium or if there is a root problem. Even a lack of sunlight can cause a cactus to turn red or reddish-green.

Why Is My Cactus Turning Red? What to do
Excessive sunlight Avoid sudden changes in sun exposure. Get the cactus used to the new light gradually.
Underwatering Water the cactus when the soil in the pot is a little less than half dry. Do not leave the cactus without water for a long time.
Drastic temperature changes Keep the cactus in a temperature range of 50°F (10°C) to 85°F (29°C). Avoid growing conditions with sudden temperature changes.
Not enough magnesium Apply magnesium sulfate. Avoid planting cactus in soil with a pH below 5.5
Root problems Use well-drained soil. Avoid overwatering the cactus. Use pots with drainage holes.
Not enough sun Place the cactus in a place with plenty of light. Increase the amount of sunlight gradually.
Diseases Buy only healthy plants. Give your cactus enough sun. Avoid overwatering. Use fungicides for treatment.

Excessive sunlight

Cactus turning red

Cactus turning red because of too much sun.

The cells of most plants contain anthocyanins. These are pigmented substances of red and other colors that the plant uses to protect itself from negative influences or for other purposes.

When too much sunlight is present, the cactus releases red anthocyanins to reduce the amount of green chlorophyll and thus keep the cells from being destroyed by excessive UV light.

Light problems most often occur in the spring. In winter, there are usually few sunny days and the daylight hours are short. The cactus gets used to these conditions and when spring arrives and there is a lot of light, it has no time to adapt, so it releases a red pigment to protect itself.

This situation can also occur when you move your cactus indoors to the outdoors for summer keeping, or from the east window to the south window. It is also worth noting here that not all cacti react by turning red when the light changes. Some cactus species are very resistant to the sun and nothing like this happens to them.

Most cacti need at least 6-8 hours of direct sun. If you take it outdoors or to a southern window, place it so it only gets direct light half the day, or shade it by opening it up to the full sun for a few hours a day.

It’s best if it gets six hours of sun in the morning and light shade the rest of the time. Gradually increase the number of hours of sunlight until your cactus can handle a full day of sun without turning red.

Read also: What hydroponics system is the best?


Not enough water can cause redness of the leaves, not only the cactus but also many other succulents. The shape of the cactus also changes, becoming smaller and wrinkled.

The reason why a cactus changes color in a drought is that it tries to reduce photosynthesis to lose less water. As a result, there is less chlorophyll and the color becomes more reddish or brownish-green.

If this is your case, that is, in addition to the redness, the cactus has changed shape, then you need to water your plant. Just because cacti can withstand long periods of drought does not mean that they do not like water. On the contrary, they do like a good watering but not very often.

Check the moisture of the soil in the pot, if it is more than 2 inches dry, it’s time to water the cactus. On a sunny window in hot weather, pots dry out very quickly, so you need to keep an eye on this regularly. Give the cactus plenty of water to soak the soil well and let it absorb as much moisture as possible. The next watering should not be done before the pot is at least 2 to 3 inches or even half dry.

You also need to make sure that the pot has drainage holes so that the excess water can drain out. Be sure you are using the right soil. Cacti like well-drained and loose soil with the addition of perlite and small stones. It is better if you use ready-made succulent dirt from the garden store.

Drastic temperature changes

Cactus turning red because of temperature stress

Cactus turning red because of temperature stress

A sudden increase or decrease in ambient temperature will definitely cause the cactus to turn red. As in the previous cases, the plant will secrete anthocyanins which will prevent, or to be precise, slow down the destruction of cells by oxygen.

Temperature fluctuations can occur for various reasons. For example, your cactus was growing indoors and you took it outdoors for the summer. But at night the air temperature dropped drastically, and the cactus changed color. The same can happen even if the cactus is growing outside all the time, but a sudden cold snap after a hot day will cause stress and the plant will change.

Even placing the cactus near an air conditioner or refrigerator can lead to a similar result.

Also, extreme heat can cause a negative reaction of the cactus even though it is a desert plant. It all depends on the type of cactus. Also, you should not place this plant near heaters or where it is very hot for some reason.

In general, cacti prefer temperatures no lower than 50°F (10°C) and no higher than 85°F (29°C). If you go outside of these limits, the plants may suffer. If the cactus turns red from temperature changes, it will recover after a while, but you still need to provide it with milder conditions to avoid trouble later on.

Not enough magnesium

Salts play a crucial role in the development of all organisms on earth and the cactus is no exception. In addition to nitrogen, phosphorus, and potassium, plants need magnesium for photosynthesis, and if it is not enough, the process slows down. As a result, the cactus turns pale reddish-green and the leaves start to wilt.

Magnesium is present in the environment in the form of sulfate. In nature, magnesium for plants is usually sufficient in the soil or water. Therefore, wild plants rarely feel a lack of this element. But things are different at home, we use specially prepared soil for cacti that still might not contain enough magnesium sulfate. The same is true of the water we give the cacti.

To remedy this you have to use a magnesium fertilizer. You can use a compound fertilizer with all the necessary elements or you can use magnesium sulfate directly. There are many good products for this purpose in garden stores. One of the best is Epsom Salt, which, in addition to magnesium, also contains other elements necessary for the plant. As a result, your cactus will not only change color to green, but it will also grow a little better.

Root problems

Cactus turning red due to root rot

Cactus turning red due to root rot.

Root rot can cause the cactus to turn red. In this case, the plant will also shrivel up and you may smell a foul odor at the base of the cactus. This often happens if you use very moist soil or water too often. Problems with the root system can even occur if the temperature is not right or if there is not enough sunlight.

Fortunately, the cactus can do without roots for a while due to the large water reserves in the leaves. During this time, it can grow a new root system and fully recover if properly treated.

If root rot is the cause of the cactus’s loss of roots, you will first have to stop watering completely. The next thing is to remove the cactus from the pot and clean all the soil from the roots. Then use a sterile tool to remove all the rotten roots and other parts of the plant if they have begun to rot. Be careful not to damage any healthy tissue.

Treat the wounds with hydrogen peroxide or fungicide and sprinkle with crushed wood ashes. Next, place the cactus in a pot with clean drained soil, the pot should have plenty of drainage holes. Place the pot in the shade and do not water the cactus for a few weeks. Then start watering in small portions. If the cactus begins to recover, gradually accustom it to direct sunlight.

Not enough sun

Both too much and too little sunlight can cause the cactus to turn red. With low amounts of light, the cactus releases the same red pigment to reduce the intensity of photosynthesis and consequently slow down growth. As a result, it becomes less elongated when there is a lack of light.

If you keep a cactus in a place with little direct sunlight and it turns slightly red, you should definitely give it more light. But don’t expose it to full sun right away, this will only aggravate the situation. If the plant is used to growing in the shade, it will get burns if moved into full sun. The amount of light should be increased gradually.

Move the cactus to a place where it will get a few hours of direct morning sun and watch how it reacts. If the redness has disappeared then give it a little more light, but if the red does not go away then move the cactus back to its old spot and look for other reasons for the color change.

It’s hard to say how much light a particular species needs. Different types of cacti need different amounts of sunlight. You have to experiment to find out how much sun your plant needs.


Diseases are the last possible cause of cactus redness on this list. In most cases, the cactus is affected by fungal diseases that are caused by various pathogens. In addition to the redness, it can get various spots on its leaves.

The reason why the cactus is sick is that it is not properly cared for. Not enough sun, not enough soil, not enough ventilation, all this and more can cause disease of your plant.

To avoid this, you have to first use the right soil, about this I wrote above. But in short, it’s better if you use a good quality succulent substrate.

Also, inspect the plant before buying. Quarantine the cactus after purchase and keep an eye on it for a few weeks.

The room where the cactus grows should have enough light, we have already talked about this. There should also be good ventilation around it and a warm temperature. The main cause of cactus diseases is overwatering. How to water cacti correctly can be read above.

If the disease happens, spray the cactus with an aqueous solution of fungicide. You can find suitable products on the market. A single spray may not be enough, so repeat it after some time.