Last summer I left most of my cacti outside in the sun after repotting them but after a few weeks, I noticed that quite a few of them looked burned. At least 4 of them have brown and shriveled stems. Please tell me my cacti will be ok. ~ By, Vulcan
Cactus sunburn is a fairly common problem. People often think because cacti grow in deserts this means that they can expose their cactus to full sun. Most cacti do like a sunny spot but they must be exposed slowly by acclimating them in increments to the exposure. But your cacti can be saved, within this blog post, we'll go over a step by step guide on how to save your cactus from sunburn and how to prevent it!
In the case of, Vulcan mentioned above, the main problem with her cacti seems to be that she had recently repotted her cactus plants. The last thing you should do with freshly repotted plants is put them in the sun. After repotting your cacti they should be put into a shady corner and not watered for at least one or two weeks. This helps your cactus adapt and give them the chance to grow back damaged roots. When your cactus is ready for it, gradually introduce her to a sunny spot.
What is cactus sunburn
It's a misconception that cacti grow in deserts. Nothing can grow in a true desert, but many cacti do grow in very dry areas. Cacti can grow in a wide variety of growth habitats, ranging from tropical rainforests to every habitat in between. Unless you are a long time cactus hoarder, a good chance that you may not be aware of the region and conditions that your cactus would ordinarily thrive in. The yellowing of your cactus plant is telling you that it isn't happy with its current conditions. And that you should try something different.
Exposing your cactus to conditions they can't handle or adapt to will result in sunburn and shriveling of your cactus. So the problem is not that some cacti don't have defensive features for extreme heat and sunlight, it's that the slow-growing nature of cacti makes them vulnerable to being placed suddenly in unfamiliar conditions.
Why is your cactus getting sunburned
Suddenly changing the growth conditions
Depending on the characteristics of your cactus most cacti like a little heat, but they need the chance to adapt to it. Almost every cactus you will find in your local store is grown in a commercial greenhouse. The conditions these cacti grow in are pretty consistent. When you bring your new cactus home and put it out in the sun, the conditions change drastically. Exposing your cacti to the sun at this point will sunburn your cactus within just a few hours.
Another important aspect is that you need to be careful when moving your cactus from one place to another. If a cactus has been growing with one side toward the south, where your cactus is exposed to the sun, and the other side to the shadier north, turning it 180 degrees could be a fatal mistake. When the side that has been shaded suddenly is hit with direct sun, it can burn in a matter of hours.
The same concern is important when your cactus has been growing under shade-cloth, where some of the sun’s rays are filtered out. If your cactus is suddenly moved to full sun, it easily can be scorched, even if its native habitat is a hot desert. It is the abruptness of the change that causes the problem. Moving your cacti little by little into more sunnier places gives it time to adjust and adapt.
Your cactus original habitat
The cactus family is a large one, and the habitats where different kinds grow can vary drastically. Jungle cactuses, for example, grow on branches in filtered light. But you will also find cacti along the foggy coast of Baja California. You will even find cacti in the high Andes of South America. Others grow happily in the blazing heat of the Arizona desert. Learning about where your cactus is found in nature can offer important clues as to what conditions they prefer to live in.
Even when you know the original habitat of your cactus, pay attention to the conditions your cacti have been in and are in. If you are bringing your cacti out from inside after the winter care should be taken to introduce them to the direct sun gradually.
How to know when your cactus is getting sunburned
When you start to see yellow or white marks on your cactus you are probably a little bit late. These marks will stay a lot longer than it took to create them in the first place. When you see your cactus starting to shrivel you might want to look at moving them to a less sunny spot.
However, sometimes a cactus will respond to hot weather by changing from green to yellow-green, This is likely more stress than burn but a pre-sign of sunburn. This change does not leave a scar, and the plant normally greens up again when temperatures drop. The stressed tissue will return to normal.
How to save your sunburned cactus
After a cactus is sunburned, the affected area becomes bleached out and remains permanently scarred. Often this area becomes a white spot but this should not be something to worry about. This is not a serious concern for a plant such as an Echeveria, because it will soon grow new leaves and sheds the old ones. On the other hand, a cactus stem stays disfigured forever.
The marks are there forever, but the good news is that as your cactus grows the damaged parts will be covered up. Your cacti should recover, but will probably remain unsightly if they are burned real bad.
Step 1, Move your cactus away from the sun
When you see your cacti yellowing or shriveling and it gets direct sunlight, obviously get them out of the hot sun. Even if this means that you have to move your cacti in and out of the sun from day to day.
Of course, this is only possible for your cacti with a smaller planter size. If you face a sunburn problem with one of your bigger cacti, you might want to use shade cloth for the hottest parts of the day.
Step 2, Extra water your cactus
If your cactus is sunburned or stressed because of too much sun, a good chance your cacti will go dormant. This means that it will go in a phase where it is not going to be growing for some time. Over this period your cactus will try to repair the damage and re-establish itself. Don't be tempted to overwater a dormant plant.
Step 3, Protect your cactus from further disease
If your cactus got sunburned it is gotten a lot weaker and therefore more susceptible to disease and infestation. Check for ants and bugs that might do more damage than the sun had already done. Be prepared to spray and treat your plants if any diseases or bugs show up.
How to prevent sunburn of your cactus in the future
When you move your plants outside in the early spring after they spend the winter indoors be careful with putting them in the sun. The easiest thing to do would be to use a shade cloth to protect them from the sun, although I feel in most climates this isn't necessary early on in the spring. It would be better to physically move your plants around, in and out of sunlight from day to day.
Fun fact, Cacti aren't able to move or put on sunscreen so they may need your help when dealing with the elements. Move your cacti around depending on what you feel their light requirements are.