Why is My Cactus Turning Purple?

Looking over at your cactus one day, you see that it has turned a purple color. What could it mean you think to yourself.

Why is my cactus turning purple? Usually, cactus will turn purple because of stress factors like cold temperatures, root rot, drought, nutritional deficiencies, excess sunlight or crowded roots. In many cases, overwatering your cactus can cause it to turn purple.

If you’d like to learn more about what causes your cactus to turn purple, keep reading because we will explore this subject in depth.

The Science behind Why Cacti Turn Purple

Cacti have chemicals in them called betalains. When the cactus juices become more acidic, you may see the cactus start to turn reddish, but when the juices go base, they become more normal. As the stressors mess with the pH balance in the cactus, the green chlorophyll in the cactus turns the color purple.

To sum it up, the chemical imbalance in your cactus has caused it to change to the purple color.

Pinpoint the Cause of It Turning Purple

First, figure out why the cactus has turned purple. In most cases, when a cactus stresses out and turns colors, it wants to tell you that something has gone wrong in its environment. Once you have figured out the cause, you can address it. Unaddressed stressors can kill your cactus.

The most dangerous stressors to watch out for include:

  • Root rot
  • Drought
  • Nutritional deficiencies
  • Crowded roots

Don’t consider the purple color undesirable in all cases because you have specific species of cactus that famously turn purple like the Santa Rita Prickly Pear. In fact, that purple spot could even be a fruit. The color ranges anywhere from reddish green to purple. It depends on the plant.

Another example of a cactus known for turning purple is the Stenocereus. In some cases, the purple color marks a natural part of their cycle as they turn to purple for the dry and cold seasons. During the winter season, you may see the leaf pads develop a tinge of purple.

Deep Purple on Cactus: Big Warning Sign

A cactus with a deep purple color should ring the alarm bells because as we said before cactus turn purple through betalaines. The more stressed a cactus becomes, the more betalaines it produces. It could mean that your cactus has a serious danger of dying. In combination with any of the following signs, your cactus could be on the verge of dying:

  • Discolored scabs
  • Small sunken spots
  • Wilting
  • Soggy texture or oozing
  • Soft spots

Purple Cactus from Too Much Sunlight?

Believe it or not, cacti can turn purple because of too much sunlight—imagine that of a desert plant. In particular, you should exercise caution when you move a cactus from a shadier part to an area with full sunlight. The sudden change can cause them to respond by turning purple. If this is the cause, you will see parts of or the whole cactus turn purple as a result.

To remedy this problem, move the cactus into an area with slightly less direct sunlight. In general, you want your cactus to have indirect sunlight because it fares better. The purple could indicate that the sun scorched its skin: Basically, the cactus has a sunburn. If you suspect sunburn, try to keep the cactus shaded with a cloth at least during the hottest part of the day, which is usually around 3 pm. You may also want to move the cactus into an area with less direct sunlight. If left unchecked, the purple can eventually turn the cactus black, killing it.

In some cases, the excess sun can damage the roots because of overheated roots. Be aware of how frequently you water your cactus as well. Cactus only require a watering thoroughly once a week.

What if the Purple is a Fruit?

You have cases where the outside of the cactus is a purple fruit that tastes delicious. First, cut off the outside skin. Cut off the top and the bottom of the fruit. During the processing, you may want to use gloves to protect your hands. Even the little pricks can get under your skin. While cactus spines aren’t poisonous, they itch, and in some cases, it can put harmful bacteria into your body that you don’t want getting in. The fruit tastes good, and you can eat it along with the pulp. This is known as the prickly pear fruit, and it comes with multiple health benefits like:

  • Control of hangovers
  • Lowering cholesterol
  • Treating diabetes
  • Helping with obesity

Health experts love this purple fruit for its anti-inflammatory and anti-viral benefits as well.

Root Rot Turns Cactus Purple?

In particular, purple leaves could indicate that your cactus suffers from root rot. Most often, root rot happens when you have poor drainage and overwater the cactus. Pay close attention to the soil. Cactus soil shouldn’t hold water in too well. It’s a special kind of soil that drains incredibly well. We’ve spoken about this previously in the article, “Can You Use Cactus Soil for Other Plants?”

As the cactus gets too much water, it can no longer take in more water and magnesium. This leads to the cactus turning purple. Root rot, if not addressed in time, will kill your cactus. You address this problem through replanting the cactus in new soil that drains better and don’t overewater it. Once a week will be plenty of water for your cactus.

Expert Tip: Other telltale signs will usually show up in your cactus like shaky roots, discoloration and mushy roots. Pay attention to all signs. In some cases, your cactus may not be purple. It could be black or yellow and have root rot.

Buying a cactus from a store doesn’t preclude it from root rot. In some cases, you can get root rot right from the store that you bought the cactus. Not only that, but you can bring home pests from plants that were in the soil from the store. Issues with the root system can prove tricky to treat in comparison to topical problems for obvious reasons.

Nutritional Deficiencies

Phosphorous deficiencies have a reputation for turning cacti purple. Not only will this turn your cactus purple, but a phosphorous deficiency will cause the cactus not to flower and not bear fruits as much. Pay attention to the leaves. If you see that the cactus has begun to turn purple, this could largely be because of how it needs more phosphorous. All plants need this nutrient because it helps the plant to create sugars, energy and nucleic acid.

Young cacti have a higher risk of having a phosphorous deficiency than an older cactus. Have you fertilized your cactus? Other common nutrient deficiencies in cacti include nitrogen deficiencies and potassium deficiencies. A lack of nitrogen will cause the growth to slow down, and the stem may turn yellow. It could cause your cactus to turn yellow. Lacking potassium, your cactus will not grow as much, and the leaves may wilt.

Having a purple or red cactus could also indicate a magnesium deficiency. Plants need magnesium for several important functions like:

  • Making chlorophyll
  • Acts as a phosphorous carrier
  • Essential for phosphate metabolism

The symptoms of magnesium deficiency will first appear on the lower leaves. It shows up as more severe on the lower leaves because of how the plant moves the magnesium to make new growth.

Fertilizer can help you to treat a deficiency whether a magnesium deficiency or a phosphorous deficiency. Monterrey LG 7220 is one of the fertilizers that you might use to treat a deficiency. This can also help plants when it comes to absorbing phosphorous. You can also use this to kill weeds in the garden. Read the instructions to learn how to apply it to your cactus.

Roots Too Crowded

Using too small of a container can lead to the roots getting crowded. As this happens, they can’t absorb the nutrients and water as effectively. One signs of crowded roots is that when you pull of soil, the soil and the plant both tend to come out of the soil at the same time. You get one big clump. Along with that, the roots may be seen coming out of the drainage part of your pot.

Some plant experts call this Pot Bound. Crowded roots can cause your cactus to turn purple because of how it doesn’t absorb the nutrients that it needs. It leads to a nutrient deficiency but in another way. Typically, you want to repot your plants every 24 to 48 months to keep the roots from overcrowding. This depends on how actively the cactus has grown. Faster growing plants, you want to plant it every 12 to 18 months. Normally, you want to repot your cactus in the early spring of the year before the grow season begins.

Before you repot your cactus, first check the new soil for pests. You want to select a container that will be one size larger than the last one that you had it in. Someone might be thinking to go with a larger pot, but too small of a pot can turn your cactus purple, and too big of a pot can make your cactus susceptible to root rot as the soil dries. This can also turn the cactus purple because it may not have the ability to absorb the nutrients correctly.

Cactus Cysts

Some cacti will naturally turn purple, but the purple could also indicate disease in some cacti. Ornamental cactus plants have a special vulnerability to cactus cysts. It usually happens because of a pest known as a nematode infests the cactus. Along with the purple color of your cactus plant, other signs of a cactus cyst include:

  • Stunted growth
  • Wilting
  • Dying leaves
  • Reduced flower production

The pest known for causing cactus cysts also attacks the roots, which can cause root rot. This opens the door to other pests and fungi getting your cactus. Perhaps the most obvious sign that you have a cactus cyst is that the roots will have white spheres that appear on it.

Suggested Article: Why is My Easter Cactus Dropping Leaves?

An ounce of prevention is better than a pound of the cure: That especially becomes true with cactus cysts. Once the infection takes root in your cactus, you will have a hard time stopping it. You will have an easier time throwing it in the garbage over stopping the infection.

To treat this pest, rotate your plants because the nematodes can’t survive without a host. They will die. Don’t plant your cactus in infected soil. That will go a long way to protecting your cactus. Sterilize the soil when you plant the cactus in a new pot. You can sterilize it through putting soil in a microwave and leaving the to of it open. Microwave the soil until it reaches a temperature of 180 degrees Fahrenheit. This will prevent your soil from being infected and turning the cactus purple.


You have a few reasons why your cactus might turn purple. Hopefully, you have come to learn about this phenomenon and how to best address it. How you deal with a purple cactus will depend on the cause of the problem. For example, excess sunlight is an easy enough problem to solve. Nutritional deficiencies are also fairly easy to resolve. Cactus cysts, however, require a quick response if you can ever hope to save your cactus.



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