Succulents are low-maintenance plants, but, like all plants, they can also suffer from diseases. Some may develop brown spots and become wilted or deformed. Certain factors may contribute to the physical damage they endure, including natural conditions such as the temperature or heavy winds and rain.
Why are there brown spots on succulents?
These are the top causes for brown spots on succulents:
1. It is due to fungus or water warts.
Fungal infections or diseases are characterized by brown or black spots that are round-shaped. These spots tend to grow and spread to the entire leaf until it eventually shrivels and falls off. The spots can also develop into warts or scabs. Fungal infections tend to occur if there is too much moisture in the air.
Some succulents are more prone to fungal diseases, such as the Echeveria Black Knight, Pachyphytum Fittkaui, Echeveria Purpusorum, and Graptoveria Amethorum.
Fungicides are the best treatment for fungal infections. They should be applied every other week during high humidity seasons. Succulents should be watered once a week, especially if the weather is exceedingly hot. Do not spray the leaves; it won’t help because the plants cannot absorb water well through the leaves.
Water should be placed around the root area, especially for sensitive succulent varieties. Make sure that you use succulent potting soil or high-draining soil that won’t hold water. If the rot due to the brown spots has not reached the top part of the plant yet, you can cut off the rotting leaves and plant them as cuttings.
2. It is due to sunburn.
Succulents can also get sunburned if exposed to the sun for a long period of time. Different varieties have varying tolerance levels for the sun, but most succulents cannot tolerate temperatures above 104 degrees Fahrenheit. An important thing to remember is that forecast temperatures are shade temperatures.
If a thermometer is placed under the sun during the hottest part of the day, what is recorded would be more than what the forecast says. Think carefully about where you are placing your succulents during the hotter parts of the day.
Succulents in pots are more prone to sunburn than those planted in the garden since the roots stay cooler when in the ground. They also react differently to high temperatures. Some plants may have droopy leaves, while others collapse in a heap of mush and develop dark-colored marks or spots.
To protect your succulents from sunburn, move them to a shaded area when there are heat waves or when the weather becomes too hot. Some plant owners place a shade cloth or an umbrella above their plants if they are too hard to move.
3. It is due to frost.
Just as the sun can have harmful effects on succulents, frost also has similar consequences. Dark spots could develop. If the frost is too severe, the plants could collapse. Succulents may show varying degrees of damage depending on how long temperatures stay below freezing.
When moisture in the plant cells freezes, it expands and bursts the cell walls, turning leaves into mush. The tips of leaves may show damage or frost burn during a light frost. During a hard frost, when the temperatures stay below freezing for hours, the cold can cause the plants to collapse. Unfortunately, succulents do not regenerate from the roots.
Succulents that cannot withstand cold temperatures and are considered tender plants include crassulas, aeoniums, kalanchoes and euphorbias. However, there are some succulents that can survive temperatures below 32 degrees Fahrenheit.
Protect your plants from frost by placing a frost cloth over them. Most succulents are not frost resistant, so you may need to bring them indoors during the winter.
4. It is due to puncture marks and scratches.
Succulents can also develop brown spots when something falls on them or when their foliage is damaged because of natural calamities like hail or heavy rain. Some varieties are more prone to puncture marks and scratches, especially those with thick farina (the dusty coating on the leaves).
Just as you care for your succulents during extreme temperature changes, it is ideal to bring your plants inside your home when facing extreme weather. This will provide them protection from punctures and scratches. You can also place them in a greenhouse or put them in a secured area.
5. It is due to pests.
Some common pests that may invade your succulents are mealybugs, aphids, and ants. They suck on the watery sap of the leaves, which can lead to brown and black spots. Slugs and snails can also poke at the leaves, which causes brown spots later on.
Eliminate pests with pyrethrum-based sprays, or wash them off by spraying them with water. Rubbing alcohol can also be sprayed on the leaves of the plants.
Succulents can also suffer from edema, or the abnormal retention of water. This can lead to brown spots and is caused by water intake through the roots that outstrips the rate of transpiration among the plants. This could be because of overwatering and the lack of draining holes in pots.
Dissolved salts and chemicals can also lead to brown spots. If you administer too many fertilizers, the salts in fertilizers can accumulate in the soil and burn the roots. When the saline solution moves up through the plants, it can burn the leaves and result in brown spots.
Succulents are easy to cultivate and do not require too much attention, but they can suffer brown spots and diseases. These spots could be due to frost, fungal infections, or sunburn. Other causes include pests, puncture marks, and dissolved salts and chemicals.
Image: istockphoto.com / Anastasiia Atamanchuk