Oh no, you’ve scorched your plants! What do you do now?
Whether it’s from receiving a shipment or spotting a plant you just couldn’t live without at the store, you recently acquired a new cactus or succulent. You diligently researched their needs, and know the perfect spot to place your new plant pal. You might repot it, you might not, or you might plant it directly in the ground. The end result is what breaks your heart:
After only a day (or even only a few hours!) it suddenly doesn’t look right anymore. The flesh is pale, the leaves may be curling dramatically or shrivelled, and it overall just doesn’t look good.
Your plant has been sunburnt! This is also commonly called “scorch”, but the meaning is the same.
If you’re not sure what that looks like, here’s a couple photos of plants that I’ve scorched. Even as an increasingly experienced grower, I still make mistakes – usually related to how much faith I’ve recently put into our weather predictions for the day.
Sunburnt Aloe “Christmas Sleigh”
Can A Plant Recover From Sunburn?
The good news is that yes, your plant can recover from sunburn if it’s not too bad. The bad news is that the sunburnt parts of the plant will never go away; it’ll always have a scar if it does pull through.
What does “not too bad” mean, though, when your cactus or succulent gets scorched? What point is “too far”?
This sunburnt lithops will probably end up melting into goo and dying, but I’m keeping it just in case. You can see some of the intact, non-damaged plant body off on one side, but the sunburn has really damaged the side of the plant down close to the roots. The top of the body, though, is still relatively good looking, so I give it about a 50/50 chance that it’ll split and recover.
This pleiospilos nelii “royal flush” has had a really bad day – not only did it get super scorched, but a chicken tried to eat it. While it’s bright yellow and soft, the sides are still purple/green, and it hasn’t turned to mush. This one also has about a 50/50 chance of pulling through if it’s cared for well and protected from further damage. Especially the chicken-related kind.
“Not too bad” can also refer to the first two plant examples shown in this post. Both the cactus and aloe have scorched areas on the plant, but the overall plant is fine. When it comes to cacti, as long as the roots are okay, the rest of the plant will probably pull through. Case in point being my baby Ariocarpus hintonii – I received it as a perfect little green cactus, potted it up, and promptly burnt it into being unrecognizable. It’s still alive and growing, though, and will eventually grow out the damaged leaves.
What Makes a Plant More Susceptible to Sunburn?
While the cause of sunburn or scorch can seem painfully obvious (the sun, duh), there’s actually a few factors that go into whether a cactus or succulent is likely to become sunburnt when exposed to sunlight.
1: Growing conditions – Exposure to Light
If the plant was raised in a greenhouse before you took it home or unpacked it, then it’s much more likely to be prone to sunburn when you first set it outside. Nursery growing conditions are typically lower light conditions than full sun, and are intentionally set up so the plant gets the best possible conditions to grow as quickly as possible. When you take your plant from a nursery or greenhouse straight to your home, and put it outside in an area with full sun (like the care information may specify!), the sudden change in light exposure can be too much. It’s very similar to how we get sunburned as humans. When you’ve worked inside most of the day and are only outdoors fully covered, in long sleeve shirts or jackets, pants, and shoes, you get very sunburnt very fast when you go to the beach in your bathing suit for the first time of the year.
However, if you’re constantly out at the beach, or just working in the yard in shorts and a t-shirt, the parts of your skin that are used to the sun will be tan and darker. Even if your skin tone is naturally darker, you still can become sunburnt if you go from spending most of the day indoors to a full day outdoors. Your skin needs to become used to the light level to protect you. In the case of humans, that’s melanin. In cacti, they have a number of adaptations to protect themselves from sun. Some species develop more spines, such as the gymnocalycium family or ferocactus family, while others get wooly coverings either over their entire body, or just where new growth is emerging. Succulents darken, although the reason isn’t likely to be melanin. I don’t know what the mechanism is for succulents darkening in response to bright sun, but they also darken in response to low watering, so it’s more of a stress reaction than one to guard against sunlight.
In any case, you need to slowly acclimate your plant to sunlight at your home or yard before leaving it to fend for itself. Even plants grown in hot greenhouses in the Arizona desert need time to adjust to full sunlight. A greenhouse may have polycarbonate walls and ceilings, shade cloth, or glass to make conditions inside more protected for the plants being grown. This protection means that the cacti or succulents grown this way are adapted to the shaded conditions in the greenhouse.
This is triple the case when the cactus or succulent was purchased from somewhere that kept them indoors, either under grow lights or just out on shelves as a free for all. The longer a cactus or succulent is kept indoors, the longer it should be given to adjust to outdoor lighting conditions.
2: Growing Conditions – Temperature
Tied very closely to exposure to sunlight is the temperature associated with the amount of sunlight. The hotter it is the more susceptible a plant will be to sunburning quickly, although cool weather does not necessarily mean a plant won’t scorch if suddenly exposed to full sun.
The biggest thing to be aware of when it comes to temperature is generally that the more significant the change in temperature between where you got the plant and your home, the more likely it is the plant may get scorched if exposed to full sunlight. If it’s gone from your air conditioned home in spring to fully outdoors in summer, that represents a dramatic temperature change that the cactus or succulent may not adapt well to. When you think about the plants that are displayed inside a large, air conditioned home improvement store, it’s easy to see how the change in temperature and lighting can have a harsh impact on your cactus.
3: Growing Conditions – Watering
It’s important when you first bring home your new cactus or succulent to check how dry the soil is, and consider the other environmental conditions before choosing to water it that day. If it’ll be cloudy and cool, chances are, you can skip watering. If it’ll be hot and bright, make sure the cactus has plenty to drink that evening. Any new plants you bring home on a hot, sunny day should go straight into the shade or even be kept protected indoors until the weather cools down. On hot and bright days, a cactus or succulent that’s been grown outdoors in full sun and has been watered sufficiently will be just fine.
A new plant that’s been indoors, shaded, or otherwise in any conditions besides those at your home…needs help. The dryer the plant is when you bring it home, the more susceptible it will be to sunburn. This doesn’t mean you should water it right away though! While watering midday is often blamed for sunburn, it’s not usually the case. I’ll talk more on that in a later post, but basically, if your plant has smooth leaves (like smooth cacti or succulents), watering it during the day won’t do it much harm.
HOWEVER, as I mention in my post about watering cacti during a heat wave, they really get the most benefit by being watered at night. It’s when their stomata (planty pores, basically) are open to capture cooler, higher humidity night air, and they are happy to get moisture at that point. Succulents benefit from this nighttime watering as well, but more because they have more time to absorb the water in the ground around them.
Helping Your Plant Recover From Sunburn or Scorch
Even if you try your best, sometimes, you may still have some plants that end up scorched. It’s okay! It happens. If you catch it early, you can still save your plants.
The main thing to look for when evaluating your plant after sunburn is how damaged the leaves are, and whether the plant’s roots are still okay. Depending on the species, if the roots surive, the plant will put out new growth (as in the case of the Saddest Ariocarpus Baby above). If only one side of the plant is sunburnt, then the rest can still conduct photosynthesis and keep the plant alive. It’s important to remember that sunburn actually kills parts of the plant that have chlorophyll, so the more sunburnt a cactus or succulent is, the less area there is for photosynthesis to take place. Plants with substantial root systems can get by and push out new growth to compensate, but species that have very small, fine root systems may not have the ability to bounce back.
You’ll want to baby your sunburnt cactus or succulent quite a bit until it shows new growth, although “babying” means different things depending on the species. If you have a copiapoa, for example, like the one below that I sunburned the first week I received it, you’ll want to keep watering to a minimum and instead, give it shade until new growth is more visible. The one below was sunburned in April of 2020, and now (Sept 2020), it has put out significant new growth, bloomed all summer long, and is producing seeds regularly. It’s also now in full sun nearly all day, and has not scorched since. It just needed time to adapt to my area!
On the other hand, this Echeveria “Lilacina” got terribly scorched during our last heat wave. I have it in an area that is in very bright indirect light, but shaded from direct sun for the vast majority of the day. When it was scorched, I’d had it for over a year, and the sunburn happened as a result of watering too late in the morning, plus the plant being in a slightly different spot on the shelf, leading to immediate bright, hot sunlight on tender areas of the plant. This led to pretty blushing when the weather was milder, but was too much for it when temperatures climbed high early in the day. It’s recovering now with new growth, thanks to more shade, maintaining a diligent watering routine (not too often, but not too little), and a month straight of mild weather. You can see that the plant is currently lopsided, and that some of the leaves are misshapen. The newest growth in the center is compact, pale blue, and has the fine farina that is the reason I ordered this plant in the first place. It was quite large before being sunburned, nearly big enough for a 6″ pot, but the burn really took out most of the older, larger leaves. Until it has recovered more, I am avoiding repotting it or otherwise causing it stress.
Sunburn Vs Sun Stress
I’ll wrap this up by quickly reviewing the difference between intentionally stressing your plant with sunlight, and actual sunburn.
Sunburn damages the plant body or leaves of your plant, “cooking” the cells and burning them to a point where they cannot conduct photosynthesis. With enough of the plant burnt, it will die.
Sun stress, on the other hand, can cause cacti and succulents to develop incredibly striking coloration and growth. Many cacti species develop more spines or wooly covering in more sunlight, while succulents often “blush” or develop starkly constrasting colors to their unstressed state. The blushing coloration of many Echeveria hybrids is the reason they are so highly coveted in some circles, and for their most striking coloration, a delicate balance between watering stress and sun (or lighting) stress must be acheived.
One plant in my collection that has seen both extremes are my Haworthia “Fat Albert”. I have several, including some currently stocked in my Esty shop, with various levels of sun stress. Haworthia “Fat Albert” is known for the chocolatey-brown color it develops in sun, which is quite a contrast to the shiny green coloration it has when grown in shade.
I exposed my first batch of Fat Alberts to direct sunlight too quickly, and lightly scorched a couple. One plant, unfortunately, appeared to almost completely melt. I don’t have any photos, but it bleached almost completely, and there was almost no live plant left – not green, not brown, just white/yellow burnt succulent flesh. Partly out of laziness, and partly to experiment, I moved the plant to the shadiest and most protected part of my small plastic greenhouse, and then left it.
It rebounded! It did end up dying back almost entirely to the root base, but as Haworthias have large, robust root systems, that must have kept it going while recovering. Note the shiny green coloration of the new growth.
The little guy is even starting to get the sun stress coloration of his cousins. These are growing in a protected, but sunnier area of the greenhouse. When I first brought them home, I had them in the back, where they got significantly less light and were more protected for a longer portion of the day. After a few weeks, they were moved to the sunnier edge, where they have slowly developed the chocolate coloration. The slow development of a stress coloration is key; you can’t rush the color development. Too fast and they’ll burn! Pictured below is one of the Fat Alberts that has developed the best color. I have to keep up on watering them to be sure they don’t get too dry while also getting plenty of sun. Notice that the plant still has some green, and that the shape overall is still intact and fairly plump? Maintaining the coloration but not killing the plant requires walking a fine line of water, sun, and heat.
The ironic thing? This plant will almost 100% revert back to green coloration in shipping. Being in a dark box with no light tends to make all cacti and succulents revert back to the greenest versions of themselves, likely as a desperate cry for sunlight when there is none.
That’s why when you unpack an order, always give the plant time to adapt, and slowly introduce it to the area and conditions you plan to grow it in. That is the best way to ensure you do not sunburn your plants!