3 Reasons Why Cactus Plants Turn Red (3 Ways to Treat It!)
Things in nature rarely happen without a reason, so is redness in cacti a cause for alarm? Or is it a normal thing? I had the same questions when I just started caring for cacti and succulents.
Generally, cactus plants will develop redness as a result of extreme factors such as excessive sun exposure, cold temperatures averaging 40°F or lower, and underwatering. These red spots and marks can be reversed by providing the cactus with adequate water and adjusting the lighting and temperature.
Change of color in cacti happens so often, yet the cause is not always known. If this is something you’re seeing in your own cactus, worry not! Continue reading to see what exactly is the cause of it and how you can treat it!
1. Excessive Sunlight
Cacti exposed to too much sunlight for long periods will develop more pigments called betalain causing redness at the tips of their modified leaves. These red spots are an indication that the cactus is suffering from sun stress. In response, it attempts to shield itself from the excessive sun exposure.
While your cactus likely comes from hot areas like deserts, it’s important to bear in mind that this is still a plant. Cacti can also suffer from sun stress.
The amount of sun exposure a cactus gets is directly correlated to how red it becomes.
One of the most common reasons why a cactus plant might turn red is as a response to an increased amount of sun. When the cactus is exposed to large quantities of harsh and direct sun, it will start to produce more betalain.
Many people seem to believe anthocyanin can be found in cacti. Anthocyanin is another pigment found in many plants but they are replaced by nitrogen-containing betalain in cacti and are never found together in the same plant.
Betalain is a pigment that contains antioxidants that can act like sunblock and protect plant cells from too much sun exposure.
The more vivid these red spots and markings are on your cactus, the higher the concentration of betalain is.
2. Underwatering
Red spots on cactus is a sign of underwatering. Without sufficient moisture, cacti will start to shrivel up and display red spots.
This is another common problem that cacti frequently face. The general rule of thumb for growing cactus is to make sure to never overwater them due to their high sensitivity to moisture.
But is underwatering also a thing for cacti? The reality is, yes!
If your cacti starts to display dry and red tips, this is just one of the earliest signs that it is receiving too little moisture. To add to this, the base of the cactus will also look more wrinkled in appearance and less full.
Over time, the redness will eventually become brown and will expand before it shrivels and falls off entirely.
3. Low Temperatures
When cactus plants are exposed to temperatures as low as 40°F for long periods, they will gradually develop more red pigments within the leaves and stems. Additionally, the overall color of the cactus will become increasingly dull.
We talked about how betalain can be seen in cacti after being placed in an extreme amount of light. However, this pigment is also produced at a higher concentration once the cacti are placed in extreme temperatures close to 40°F (approx. 5 °C).
Cacti suffering from extreme cold will also be somewhat dull in color.
Consider checking the average temperature of the room your cacti are placed in and ask yourself, is this too cold for them?
See if your cactus can tolerate colder temperatures, as this new display of red markings might be an indication that it cannot.
Read more about this in our article discussing if your cactus can survive the cold.
3 Solutions to Treat Red Spots on Cacti
The 3 most effective ways to treat red spots on cacti are:
- Adjust the lighting accordingly
- Water the cactus regularly
- Adjust temperatures accordingly
So you think you’ve identified the reason why your cactus may be turning red. But what do you do about it now? Can it be reversed? This is what we will go over in the section below.
1. Adjust the Lighting Accordingly
Reduce the amount of sun exposure the cactus is receiving and place it in areas with partial shade. Outdoor cacti must be protected from unfiltered light with the use of plant covers or blankets. They may also be placed in the shade of bigger plants.
For cacti suffering from sun stress, the solutions can be relatively easy. Cactus plants can handle being placed in direct light but acclimation is required at first. The same can also be done for reddened succulents.
Place your cacti in different areas of your home where they can receive bright light but still have some shade. In case your cactus is being grown outside or cannot be moved, see if you can provide some shelter by shielding it with burlap.
Alternatively, you may also place something in front of it, so it can sit in the shade. Even just positioning it behind some other taller plants can help the cactus significantly.
If grow lights are being used for indoor cactus plants, they must also be occasionally turned off or reduced to help offer the poor cactus a break.
2. Water Your Cactus Regularly
To decrease redness in cacti, cactus plants must be given adequate water every 2 weeks. Water only when the substrate is completely dry and water thoroughly until puddles are seen underneath the pots’ drainage holes.
Cacti and succulents are known as the camels of the plant world for a reason. However, cacti cannot grow in absolutely dry soil where there is never any moisture present.
Full and generous watering sessions are needed as well. So it is crucial that you water the cactus to the point where excess water runs out of the drainage holes.
This means the water has drenched through all the substrates and is more likely to reach the roots!
Some ways your cactus plants will signal for more water is when the potting soil feels dry to the touch and the leaves start to shrivel.
Another key thing to mention is that misting cannot be used as an alternative means of watering cacti. Water your cactus regularly every 2 weeks or so to be certain they are receiving the moisture they require.
3. Adjust Temperatures Accordingly
Cactus plants suffering from extreme cold must be brought indoors or placed in areas with higher insulation. Outdoor cacti must be shielded from frost with the use of burlap to prevent the cactus from turning red. Ensure the topsoil is covered to increase warmth.
If your cactus is starting to turn red because of extreme temperatures, consider moving them to warmer rooms.
Some good examples of this would be a cozy room with a regularly used fireplace or even just an area with more rugs and higher insulation.
Here is one of the plant covers from Amazon that I typically recommend. These are excellent because they can be used to protect your plants from both extreme cold and extreme sun!
If you happen to live in a consistently cold area, however, consider growing a cactus that is frost-hardy. Some varieties of the prickly pear cactus are great candidates as they can survive temperatures as low as 15°F (-9°C)!
In situations where you’re unable to bring the cactus inside, try to cover the topsoil with a layer of mulch. Avoid piling it on, though, as this could trap a higher amount of moisture, leading to root rot.
Is It Bad to Let Your Cactus Turn Red?
Red leaves and markings are ultimately an indicator of the cactus adapting to its new environmental factors so it’s not necessarily bad to let them turn red. Given proper care, cacti can flourish and live for many years even while displaying redness.
Some folks find this change of color beautiful and intentionally stress their cacti to coax the vivid red hues out. This is especially common in jade plants.
On the flip side, many find the idea of purposefully stressing cacti to be mean and almost cruel. This is what my initial reaction was as well. The last thing I would want is to stress my own plants!
But the good news is that plants do not have any pain receptors. Since they don’t have brains—or even nerves—they can’t feel pain.
When your cactus starts to display signs like these, this is simply its way of signaling the changes that it is currently experiencing and activating its defense mechanisms to survive.
Many cacti have red tips and still live long and happy lives. However, if the idea of letting your plant live under stress is too much, or you prefer your plants to be nice and green, that’s fine too.
With the tips we mentioned above, you can make sure they experience the least amount of stress possible!
FAQs
Why do cactus spines turn red?
Cactus spines are typically brown or white in appearance but red spines can be commonly seen as well. This is an indicator that the cactus is experiencing new growth and producing new spines. Young cactus spines will initially be red at first and will become brown as they mature.
Is there a naturally red cactus?
The natural pigment betalain can be found in cacti and succulents alike. However, they are only visible once they are developed in higher concentration due to sun stress, extreme temperatures, and underwatering. Succulents can sometimes be sold with red tips and markings but there are no cacti varieties available where the cactus body is permanently red.
Summary of Why Cactus Turns Red
Cactus plants and succulents will usually turn red in response to extreme changes in their environment. Some of the most common factors would include underwatering, excessive sun exposure, and consistently cold temperatures around 40°F or 4.44°C.
Although the redness is a signal of stress, it is extremely popular for plant owners to purposefully stress their cacti in order for them to become more red and colorful.
Redness due to sun stress does not cause the cactus any pain and can easily be reversed by providing the cactus more shade, placing them in warmer environments, and watering them regularly after the soil has completely dried.
Sources
- “Cacti and Succulents” by n/a in University of Texas
- “CHAPTER 26 – Betalains” by H. Böhm and E. Rink in Institute of Plant Biochemistry
- “Anthocyanins and betalains: evolution of the mutually exclusive pathways” by Helen A. Stafford in Department of Biology, Reed College
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