8 Reasons Why Brown Spots on Indoor Cactus: : A Comprehensive Guide
Cacti are remarkably hardy and low-maintenance plants. Most of the time, all they require for growth is enough exposure to light, drained soil, and attentive watering. What is the cause of my cactus’ browning?
Cacti plants can turn brown, yellow, or even purple due various reasons. Sunburn, corking, rot, fungal disease, insect infestation, and animal attacks are all causes of brown blotches on cacti. Here, we’ll review the causes, remedies, and preventative measures for brown spots on indoor cactus plants.
Reasons To Brown Spots On Indoor Cactus
1. Overwatering
Brown patches might appear on an overwatered cactus. This frequently results from feeding the cactus too much water or keeping it in a pot without adequate drainage.
Because succulents and cacti don’t require much moisture, simply water the top inch of soil when it seems dry to the touch. Cactus plants generally require watering every two to four weeks. Additionally, if your cactus is in a pot without drainage, the water will collect at the bottom and be unable to evaporate. The cactus will experience root rot as a result of this.
– What To Do To Fix It
You must wait until the cactus is completely dry before watering it again if it has been overwatered. It could also need to be repotted in a pot with suitable drainage.
You can try to remedy your cactus by cutting the damaged areas of the plant and then watering it less frequently if it has grown soft brown spots as a result of overwatering.
– Prevention
Use a pot with good drainage and water your cactus just when the top inch of soil is dry to avoid overwatering. Depending on the weather and the amount of rain your cactus receives, water it every two to four weeks. You might need to water your cactus more frequently if you live in a hot, dry environment. On the other hand, you might need to water it less frequently if you live in a humid region.
2. Sunburn
The most frequent and likely cause of a cactus plant becoming brown from the top is sunburn. Given that the majority of us have a misconception that cactus are sun-loving desert plants, this may sound strange. Not all cacti species do well in intense sunlight.
Some need only a little sun and shade to grow successfully. If you don’t take the time to acclimate your newly purchased cacti plants gently to the harsh outdoor light, they could also get sunburned. The most common symptom of light sunburn is a pale discoloration on the plant’s sun-facing side. The pale areas eventually grow into dark brown scars, which is a sign of severe sunburn.
You can do nothing to repair severe brown burns on cacti plants; the damage is irreversible. However, if your plant has white patches, you can still save it by relocating it to a shaded place. It will recover completely as long as you give it shade on the warmest days of the year. To provide optimal conditions, it will also be beneficial if you take the time to learn about the lighting requirements for your plant.
– What To Do To Fix It
Reduce the amount of direct sunlight your cactus receives if it has been sunburned, and move it to a shaded place. Avoid placing it in the scorching noon sun and instead place it where it receives indirect light. If the plant has many brown patches, you might need to cut the damaged areas before watering them less frequently.
– Prevention
Ensure your cactus is in an area with indirect sunlight, and avoid placing it in the harsh midday sun to prevent sunburn. Although cacti require around six hours of direct sunlight each day, you should also offer some shade during the hottest time of the day.
Cactus plants should be located close to a window that receives indirect light when being grown inside. If you live in a hot, sunny environment, you might want to grow your outdoor cactus plants in pots so you can transfer your cactus to shady locations during the hottest time of the day.
3. Root Rot
Root rot is another typical issue that can result in brown spots on cactus plants. If untreated, this serious condition has the potential to destroy the plant. The most common cause of root rot disease is overwatering. For bacteria and fungi to flourish, the soil must not be moist for an extended period. The plant’s roots will become infected by these organisms, which will cause them to decay.
– What To Do To Fix It
You must take action to assist your cactus in recovering if it has root rot. First, stop watering it and give the soil time to completely dry out. Then, using a sharp knife, remove any rotten or damaged roots.
The cactus should then be repotted in new soil and given minimal watering until it starts developing fresh, robust roots. Be patient; the rotting cactus may not entirely recover for several months. If the cactus is highly diseased and the rot has reached the stem, you will need to cut off the afflicted area and transplant the remaining plant.
– Prevention
Water your cactus sparingly, and never allow the soil to become wet to avoid root rot. You can also improve the soil’s drainage by adding sand or perlite. Avoid overwatering by periodically monitoring the soil and only applying water when it feels dry to the touch.
4. Pests
Bug infestations almost certainly cause brown spots if carelessness can be ruled out as the reason. Brown patches form as a result of damage to the epidermis caused by stinging and sucking insects. Scale insects, aphids, and spider mites are among the offenders. Look at the affected cactus with a magnifying glass to see if bugs are there. Simple home remedies can still be used to fight the infestation in its early stages:
Scale insects: dab with cotton swabs dipped in alcohol or dust with diatomaceous earth. Use a conventional soft soap solution to spray for spider mites and aphids. You can completely cut off the pests’ access to oxygen by placing the infected cactus in an airtight plastic bag for 3 – 5 days. The brown spots may be caused by bugs if you believe your cactus is rooted in well-draining soil, isn’t being overwatered, and are receiving the correct amount of sunlight. Your cacti may develop brown spots if spider mites or scale are present.
Webbing and tiny brown spots, especially on younger growth, are the first indications of spider mites, which are microscopic intruders. Spider mites can be eliminated in a variety of methods, one of which is by spraying plants with insecticidal soap. Keep your cactus in quarantine as you administer the medicine and until you are certain that the mites are gone.
In terms of scale, they resemble little brown patches on the plant. When examined closely, the scale has brown, dome-shaped shells that adhere to the plant but are easily removed by scraping or wiping. Scale can be removed successfully by treating the afflicted regions with cotton swabs and rubbing alcohol. Until the issue is resolved, quarantine and repeat treatment which can need for some endurance.
– What To Do To Fix It
You must take steps to eradicate any pest infestations on your cactus. The most effective method for doing this is to use a natural insecticide like neem oil. Repeat as necessary after applying the oil to the afflicted areas. Additionally, be sure to frequently clean the plant’s leaves to get rid of any pests or eggs that might be hiding there. For this, you can use a gentle brush or a wet towel.
– Prevention
Maintaining a clean and healthy cactus is the greatest way to keep pests away. A few weeks of quarantine are recommended when bringing a new cactus plant home to ensure that it is free of pests. Regularly check the leaves for pest activity and treat any infestations that are found. Additionally, keep your plants in a well-lit place and avoid overcrowding. This will facilitate preventing bugs from settling there.
5. Fungal Infections
Your cactus may become sick if it is exposed to fungi or other infections. Once an infection has taken hold, getting rid of it can be incredibly difficult. The most prevalent fungus responsible for cactus anthracnose, Colletotrichum (Gleosporium) spp., permanently damages cacti. The diseased area initially appears wet and light brown. The spots eventually covered the entire plant after spreading over time. Fungal disease-infected cacti plants are considerably more likely to die.
Additionally, cactus plants are susceptible to fungal diseases, which can result in brown or black patches. Overwatering is the most frequent cause of fungus infections, although other factors like poor airflow or high humidity can also contribute to them. The dying cactus will decompose as a result of the fungus’ invasion of the stems or roots of the plant.
– What To Do To Fix It
You’ll have to take action to treat the fungus if it exists on your cactus plant. The plant should stop receiving water, and the soil should dry up. Then, using a sharp knife, cut out any sick roots or stems and throw them away. Next, apply a fungicide to the plant. Last but not least, repotted the cactus in fresh soil and carefully watered it until it started forming new roots. You can resume regular watering after the plant is back to health.
– Prevention
Make sure your cactus receives proper watering and has adequate airflow to avoid fungal infections. Keep the soil dry in between waterings, and never overwater your cactus. A high-humidity atmosphere should also be kept away from when growing cacti. Make sure to put your cactus in a dry, well-ventilated area when you bring it indoors for the winter.
6. Cactus Corking
A healthy cactus plant could suddenly develop solid, brown tissue that resembles bark a few inches above the soil’s surface. This is a symptom of corking. Fortunately, you shouldn’t be too concerned because this is a normal part of the cacti plants’ aging process. Most of the time, corking begins at the plant’s base and progresses upward. There is nothing you can do to stop the natural process of corking, which is causing your plant to turn brown. Its aging process can be slowed down by simply taking proper care of it.
– What To Do To Fix It
In the majority of situations, there is no need to take any action because cactus corking is a normal process that does not hurt the plant.
If the cactus is in a container, you may cut off the corked areas with a sharp knife to keep it from becoming too huge.
– Prevention
Cactus corking is a natural aging process that cannot be stopped; therefore, there is no known technique to stop it. But if you’re worried about the emergence of cactus corking, you may keep an eye on your plant and chop off any corked sections as soon as they emerge.
7. Frost Damage
Similar to sunburns, cacti plants may become brown where they have been damaged by frost. The only way to distinguish between frost damage and sunburn damage is by checking the temperature because the damage is pretty similar.
Cactus plant tissues that are exposed to cold temperatures experience cell rupture. The plant will attempt to self-heal by developing calluses over the harmed tissues, even if you might not immediately detect the damage. Even though the brittle spots on the plant are typically spotty, this self-healing mechanism is similar to the one that happens after a hailstorm. Frost damage can still occur on indoor plants that come into close contact with the window glass.
– What To Do To Fix It
You must remove the dead tissue from your cactus plant if it has been harmed by frost. Brown tissue should be removed with a sharp knife or pair of scissors so that healthy green tissue may be seen. It could be necessary to replant the plant if a significant percentage of it was harmed. Make sure to water your cactus plants well and use a potting mix made specifically for them.
– Prevention
Protecting your cactus plants from the cold is the best approach to avoid frost damage. When it is below freezing, either bring them inside or cover them with a blanket or sheet for protection. A sunny windowsill would be a good place to give them a warm habitat. Place them away from drafty areas such as doorways and windows.
8. Fertilizer Burn
Additionally, fertilizer burn can cause brown blotches on cacti. Overfertilization or the application of incorrect fertilizer are common causes of this. During the growing season, cactus plants only need to be treated once every two to four months because they don’t require much fertilizer. Brown patches can develop on a plant due to cell bursts brought on by overfertilization.
– What To Do To Fix It
You must take action to aid the recovery of the plant if your cactus has fertilizer burn. The first thing you should do is use less fertilizer. The plant should also be watered more often to help flush off the extra fertilizer.
Last, but not least, give the plant some time to heal; it can take a few weeks for the brown spots to go away. You might need to replant the cactus if it is seriously damaged to aid in its recovery.
– Prevention
During the growing season, cactus plants only need to be treated once every two to four months because they don’t require much fertilizer. Use a diluted fertilizer and fertilize the soil only, never the plant, when you fertilize your cactus.
Lilani graduated with a bachelor of agriculture, with a specialization in biotechnology from the Wayamba University of Sri Lanka, as well as she is following a Master’s in Molecular Life Sciences. She has a passion for writing and communicating about agriculture topics and loves enthusing people about the botanical world.
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