Exposing a cactus to too much sunlight may result in heat damage to the plant tissues. The sun-scorched effects on cacti can range from mild discoloration to severe burns that can cause the plant to die. Early identification and treatment of cactus sunburn can be helpful in saving the plant.
Sunburn can happen to any type of cactus, but it is common in species that are not adapted to the high levels of sunlight in some regions. Tender cacti plants that have been recently repotted or moved to a new location may experience a sunburn, as they may not be fully acclimated to the new levels of sunlight.
Plants raised in greenhouses also won’t withstand prolonged exposure to sunlight. They are typically used to consistently controled levels of light, temperature, and moisture. When you purchase them without prior knowledge of where they were propagated then you may mistakenly expose them to long hours of sunlight.
It’s true that cacti can perfectly handle intense heat and drought but this happens gradually as the plant grows and evolve special features that make it hard to such conditions. However, some epiphytic cacti species like the Christmas, the Easter, and the Thanksgiving cacti are naturally adapted to shady environments and they can withstand direct sunlight.
What does sunburn look like on a cactus?
Heat stress in cacti can appear in different forms. Some cactus species may take a few minutes to show signs of sun distress while others take hours or days. One of the obvious signs of sunburn is discoloration of the cactus’s skin, you’ll notice a cactus turning yellow, brown, white, or purple.
Sunburned cacti may also appear shriveled or shrunken. This is also a sign that the plant has also lost too much water to the hot sun. Without any intervention then the plant will get limp, wilt, and eventually die.
Exposure to extreme sunlight may also cause premature cactus corking. This is an aging process where the outer skin of the cactus becomes hard and scale-like. Although it doesn’t affect the health of the plant some gardeners find it very unappealing.
How to treat a sunburned cactus
Cactus sunburn can be treated in a few different ways. However, it’s important to note that once the damage has occurred, it is permanent and cannot be reversed. The following are care tips that can help heal the sun-scalded plant:
1. Provide shade
The first step in caring for a sunburned cactus is to provide it with shade. Simply move the cactus to a shaded area or cover it with a cloth or other shading material as long as it’s protected from direct sunlight.
2. Mist the plant
Misting the cactus with room-temperature water in a spray bottle can help to cool and hydrate the plant. Be careful not to overwater the soil, as this can lead to rot problems.
3. Avoid fertilizing
A sunburned cactus is already under stress, and fertilizing it may further stress the plant. Avoid fertilizing until the cactus has fully recovered.
4. Do not repot
Sunburned cacti are fragile, and it is best to wait until the cactus has fully recovered before repotting it in fresh soil. repotting is necessary when the plant has outgrown its pot or when you are saving an overwatered plant.
5. Monitor the cactus
It is important to monitor the cactus for several weeks after the sunburn to detect any secondary issues such as pests, diseases, and fungal infections. If you notice any signs, treat them immediately to prevent further damage to the plant.
6. Be keen about the weather
Keeping an eye on the weather forecast can help save the cactus from sunburn and other weather-related issues. If there is a predicted heatwave, then move the cactus to a shaded area or cover it with a shading material.
7. Acclimate the plant
Once the cactus has recovered from the sunburn, gradually reintroduce it to sunlight over a period of a few days. This will help it acclimate to the sun and prevent future sunburn.
8. Be patient
It can take several weeks or even months for a sunburned cactus to fully recover, so it is important to be patient and give the plant the time it needs to heal.
It is important to keep in mind that if the sunburn is severe, the cactus may not recover. In this case, it is best to replace it with a new one.
Can artificial lighting cause cactus sunburn?
Yes, artificial lighting can cause cactus sunburn. In most cases, this type of lighting provides a certain light spectrum that some cacti plants may not cope with. Additionally, artificial lights positioned closer to the cactus may emit intense light and heat which may harm the plant tissues.
Note that, plants may react to artificial lighting differently depending on the type of light used. It’s important to use the right type of light for the cactus and to monitor the plant for signs of sunburn. If you notice sunburn, you should move the cactus to a shaded area or provide it with UV protection.
Cactus sunburn can be prevented by meeting the recommended right light requirement of your plant. Additionally, new plants from the shaded area should be acclimatized before introducing them to long hours of sunlight. Good care should be provided to a sunburned cactus to promote faster healing and recovery from the damages.
- “Outdoor Cactus Culture” – March 20, 2019 by Jeff Schalau, Agent, Agriculture & Natural Resources University of Arizona Cooperative Extension, Yavapai County
- “Cactus Care in Your Home” by Lanie Keystone, University of California, Departments of Agriculture and Natural Resources.
My name is Diane M Lewik, and I am the founder of this website. I am a degree holder in plant biology from the University of California – Berkeley. Over years, I have cultivated a vast collection of succulents and I have learned a great deal about how to grow and care for these unique plants.