Skip to Content

Why Is My Cactus Turning Red? (8 Causes And Solutions)

Cactus leaves turning red

Cactus are hardy plants that are accustomed to challenging environments. However, certain environmental stressors can see your cactus begin to turn red.

This does not necessarily indicate an unhealthy plant, but it is a sign your plant is telling you something is amiss. The good news is you can return your plant to its natural color by modifying the plant’s care and eliminating the stressor.

Cactus turns red when it becomes stressed due to changes in environmental conditions, such as excessive heat, too much sun and lack of water. In addition to these, root infections and pathogenic infections may also see your cactus turn a shade of red.

In this article, I will list the common reasons why your cactus may turn red. By understanding the reasons a cactus is turning red we can apply solutions to help the plant recover and continue to thrive.

The red indicates the plant’s natural protection mechanisms are being employed, so the solutions provided will help the plant return to its natural color.

Stressors Causing Your Cactus to Turn Red

Anthocyanins Pigment

Anthocyanins are a pigment that helps protect your cactus against extreme environmental changes. When your cactus is subject to more extreme conditions it reacts by producing more anthocyanins in order to better protect itself.

Therefore, as more pigment is produced the more likely the cactus is to turn a shade of red. 

As this increased pigment production is a built-in protection mechanism brought about by environmental stresses you should look to reduce these stressors. The conditions which can accelerate pigment production include:

  • Too much sun.
  • Extreme changes in temperature.
  • Lack of water.

Solution

Anthocyanin pigment offers a natural protection mechanism for the wide-ranging environmental conditions cacti can experience in their natural setting. To prevent your cactus from producing too much  pigment you can:

  • Rotate your indoor cactus to the sun, ensuring an even exposure to sunlight for all sides of the plant.
  • Maintain the room at an even temperature, ensuring it never wildly fluctuates.
  • Place cactus plants away from windows or doors with cold draughts, as well as hot locations such as near fireplaces. or warm vents.
  • Keep on top of your watering and regularly check if the soil has dried out.

Magnesium Deficiency

Like you and me, cactus plants can not survive on water alone. They require nutrients to help keep them sustained and thriving. One of these important nutrients is magnesium. A lack of magnesium is another primary cause why a cactus turns red.

As well as turning red, a cactus plant deficient in magnesium may also start to wilt. Your plant is more at risk of this deficiency in colder seasons as this is when nutrient uptake tends to be at its lowest. Fortunately, there are a couple of simple solutions to correct a magnesium deficiency in your cactus plant.

Solution

The first simple solution is to pay a visit to your local garden store and purchasing a magnesium-enriched fertilizer to apply to your cactus.

By following the product instructions you should restore your plant to its natural color. However, there is also a homemade solution that could offer an even more ready-to-go remedy. For this you just need:

  • 8 tablespoons of Epsom Salts.
  • 2.5 gallons of water.
  • 1 or 2 drops of dishwashing soap.

All you need to do is mix these household ingredients and apply using a spray bottle. Make sure you spray all areas of the plant to maximize the effect. Providing you carry on applying this mixture for a couple of weeks or so your cactus should gradually return to its natural color.

Too Much Sun 

As discussed, cactus plants have built-in protection mechanisms to cope with extreme environmental changes. One of these changes is excessive exposure to sunlight, another possible cause for your cactus turning red. It is thought a cactus produces more red pigment when exposed to too much sun in order to help combat the additional UV rays.

While this reaction is therefore a natural one for the plant, you do risk damage from sunburn through inaction and the plant’s prolonged exposure to the sun.

This will have a detrimental effect on the health of the plant. Most cacti require at least four to six hours of sun every day, often more, although you should check on what is recommended for your particular species.

Solution

Most cactus plants happily thrive on indirect sunlight. Placing your cactus in a window with a south-facing view should ensure it receives the required amount of sun every day. Ultimately you want to avoid exposing your cactus to intense, direct heat when positioning your plant.

If you have a new cactus, gradually introduce it to a sunny spot to avoid potential stress. Similarly, do not move a cactus plant into a new, sunnier spot without a gradual introduction.

Lack of Water

While cacti are very resilient plants, used to drought conditions, potted home plants may start to turn red through a lack of water.

Drought is a frequent stressor for cacti in their natural environment and they have evolved mechanisms to cope.  Plants kept in pots can dry out quickly, particularly when placed in the sun for lengthy periods each day.

When your cactus starts to turn red it is a sure sign it is telling you something. You can check the plant’s soil, and if this has been allowed to dry out it could be the reason for the recent red hue to your cactus.

Solution

Once you notice the soil is dry it is time to water your cactus. Place your finger in the top of the soil to a depth of 2” as a test, and if the soil feels dry then water your plant. Although the image of a cactus is one of a hardy desert plant, they do like good watering.

Make sure the soil is drenched right through to the bottom of the pot when watering. Regularly check your plant’s soil, and when dry, water from the base of the plant.

Root Infections

Just as a lack of water can cause a stress reaction in your cactus, so can too much water. It is fairly easy to be lured into overwatering a cactus, as they have evolved to store water to deal with harsh natural climates. However, overwatering can lead to root infection and cause discoloration, particularly toward the base of the plant.

If you are using sandy soil this can compound the problem by retaining more water. If a root infection is the source of your cactus turning red it needs to be promptly addressed. Wilting is another sign alongside turning red which may indicate a root infection, as is a musty smell emanating from the pot.

Solution

Once you have identified a root infection as the cause you need to re-pot your cactus as soon as possible, using fresh, new soil. To allow time for the roots to recover, and to rid any infection, you need to avoid watering the plant for around two to three weeks.

You can prune any damaged parts of the cactus during this time, and once you are watering again, regularly monitor the soil moisture content.

Lack of Light

Just as cacti can receive too much sun exposure, a lack of light can also result in a plant turning red. Different cacti species will require different amounts of light, so it is always worthwhile checking what your particular cactus plants require.

Solution

Cactus plants need sun, whether it is full or partial. Therefore find a good, sunny spot for your plant, avoiding one which is predominantly in shade. A lack of light can also affect just one side of a cactus plant, so you can try rotating your cactus to the sun to help prevent this from becoming an issue.

Temperature Stress

Excessive temperatures at both ends of the scale may cause your cactus to turn red.  While in general cacti have evolved to cope with high temperatures, the acceptable range can still vary from species to species. Temperatures over 90°F (32°C) are best avoided as this will likely damage most cacti.

Solution

To avoid temperature stress within your cactus plant you should look to keep the room temperature between  45°F (7°C) and 85°F (29°C). Similar to addressing problems with over-exposure to the sun, you can move the plant away from a hot area to reduce its risk from temperature stress.

Pathogenic Infection

A cactus originally potted in contaminated soil can result turning red. Another cause of a pathogenic infection is propagating from an infected plant. Cactus cyst is an example of a pathogenic infection and tends to affect the roots.

As well as discoloration, this infection can cause wilting and stunted growth. Small, pearl-like masses on the roots of your cactus are a sure-fire sign of this particular infection.

Solution

A pathogenic infection can be difficult to treat, so prevention is the main aim. This includes:

  • Making sure you use fresh, sterilized soil when potting up your cactus plant.
  • Buying established cacti, removing the risk of propagation from infected plants.
  • If you are placing cacti outdoors for any period of time, look to keep them off the ground to reduce the chance of contact with infected soil.

Why Do Cactus Spines Turn Red?

It is one thing for your cactus plant to turn red, but what about if the spines turn red? In fact, you should expect your cactus spines to turn red at some point as this is part of the plant’s maturing process.

Having red spines indicates your cactus plant is growing well and healthily. When you see your cactus spines turn red you can perhaps give them a little more water to aid the growth stage it is going through.

Should You Worry About Cactus Spines Turning Red?

It would be completely understandable if you became concerned to see your cactus spines turning red. Red is a color. we associate with danger in nature and something to avoid. However, in this case, it is nothing to worry yourself about. Actually, it is something you can be pleased to see. 

Red cactus spines are a sign of a healthy plant going through a natural growth phase. If you have been caring for your cactus well and watering properly, you should expect to see red spines along the way. It is a sign you are doing right by your cactus and should carry on in the same mode. 

What Color Should Cactus Spines Be?

Although red spines are the sign of a growing cactus plant, the usual color of the spines will depend on the species. A favorite household cactus is the Christmas cactus which has green spines, yet other species can have different colored spines, including grey and yellow.

As the plant grows and matures, red spines may give way to white spines, before settling on yet a further color. All this is a natural part of the plant’s growth stages.

The one color you may be wary about seeing on your cactus spines is brown. While this could still be part of the plant’s natural growth, brown spines can sometimes indicate an infestation problem.

Again, it is recommended you gain some basic background knowledge on your cactus species in order to know what to expect and to be able to spot potential problems.

Final Words

Changes in environmental conditions can produce stressors that see a cactus plant’s natural protection mechanisms kick in. One of the ways a cactus shows it is stressed is by turning red. When you see your cactus turn red you know the plant is telling you it needs attention.

 Environmental stressors include:

  • Too much sun.
  • Temperature fluctuations.
  • Lack of water.
  • Lack of light.
  • Nutrient deficiency.

Cacti are hardy plants, but once they send out signals they are under stress you can alter your care routine to provide the environmental conditions your cactus requires to thrive. 

Cactus maintenance sources.

(Source: Washington State University, University of Vermont)