Seeing a brown spot on your plant’s leaves can be frightening, especially since it may be hard to identify the cause. Brown spots are common among indoor and outdoor plants and should always be investigated.
The brown leaves may be from watering, light, or heat issues, or a pest such as a bacteria or fungus.
Aside from biotic and environmental factors, brown spots on leaves can also occur due to nutritional problems.
Luckily, with some practice and research, you can identify these signs and symptoms on brown leaves.
Most plants can recover from brown spots on leaves if you catch it early enough, although there are a handful of cases where a plant must be destroyed to protect others.
To help save your plants, join in as we discuss the causes, treatment, and prevention of brown spots on leaves on indoor and outdoor plants!
If your houseplants are developing brown spots on their leaves, it could be from pest problems, humidity, sunburn, or a watering issue.
Since it’s difficult to identify why a plant’s leaves are turning brown, you could think of a routine you recently changed with the plant related to sun or watering.
For example, if a plant developed brown leaves after you started watering it less, it could be a watering issue.
Initially, it can be hard to identify the cause of brown spots. Certain indicators such as yellow halos around the brown spots (pictured above) can be helpful to identify the issue as a bacterial pest.
Common Causes of Browning on Houseplants
- Low humidity (common with tropical plants)
- Uneven watering patterns
- Nutrient imbalances
- Salt burn (from excess salt in the soil)
- Spider mites
- Fungal leaf spot
- Bacterial leaf spot
Treatment Options for Humidity and Watering Issues
Humidity can be the cause of brown spots on leaves, and if a plant is too dry, its leaves will be crumbly.
If it is too humid, plants will develop soggy brown tissue on their leaves.
If you’ve identified the cause of the brown spots on your indoor plant leaves as lack of humidity, here are a few treatment options:
- Put a tray of moist pebbles under your plant’s pot (rinse pebbles often to prevent mold)
- Mist your plants with water once a day
- Make a plastic dome over the top of your plant to create a greenhouse effect
If a houseplant receives too much humidity and develops brown spots on its leaves, it is too wet.
Symptoms of excess humidity include the presence of mold or fungus, wet soil, and soft brown leaves.
Monstera houseplants (pictured above) commonly struggle with humidity issues because they are naturally tropical plants. My monstera always dries out (not enough humidity), so I spritz it with water every week.
To prevent excess humidity and in turn brown spots, you could follow these tips:
- Set the plant in a drier area
- Don’t water the plant until it’s thoroughly dry
- Spray the surface of the soil with an antibacterial soap solution or neem oil
In terms of watering, a plant can develop brown spots on its leaves if it is underwatered or overwatered.
The main difference between the two is that underwatering will result in crispy brown leaf edges while overwatering will cause limp, moist brown tips or spots.
An underwatered plant will begin to lose its form due to loss of turgidity, while an overwatered plant will remain in shape but develop brown leaves. This is true for most plants but can vary from case to case.
Whether you are giving your plant too much or too little water, the main solution is to adjust your watering cycles.
Research your plant’s watering requirements and practice judging soil moisture to appropriately adjust the watering schedule.
Treatment Options for Nutrient and Sun Problems
Brown spots on leaves can sometimes be caused by sunburn, which happens when a plant is exposed to higher light than it is accustomed to.
Sunburn on indoor plants occurs when you put them outside in the sun after they have been in indoor conditions for an extended period of time.
When sunburn occurs, the sun fries the plant, leaving it with no moisture in its cells. Common symptoms of sunburn include necrosis (brown spots), chlorosis (yellow spots), and bleaching (white leaves).
Pictured here is a case of severe sunburn seeing that there are signs of bleaching. The plant was put into direct sun too quickly. The only option is to trim only a few leaves and hope for new growth.
To prevent or treat, sunburn you could follow these steps:
- Harden off all plants before putting them outside
- Trim off all dead tissue if the case is not severe
- If severe, don’t trim the plant and wait for signs of green tissue before cutting dead leaves
Nutrient imbalances can also cause brown spots on plants. Plant nutrition is highly complicated, so be sure to research what exact nutrient you may be dealing with. University extension sites are most useful for this.
For indoor plants, the most common nutrient problem that causes brown spots is salt burn. This is common in houseplants because they generally don’t receive enough drainage.
For salt burn, the symptoms include browning and yellowing at the leaf tips. An excess amount of salt in the soil (from either overfertilizing or minimal drainage) dries out the plant which is what causes the necrosis.
For prevention or treatment of salt burn, you could follow these tips:
- Wait until your plant dries out and then rinse it thoroughly until water drains out the bottom (do this for about a month)
- Avoid bottom watering
- Avoid fertilizing
Correct watering of plants is a huge way to prevent brown spots on leaves. If you have correct drainage for your pots as pictured above, you may have a better chance of developing a satisfactory watering schedule.
Nutrients can cause brown spots if there is excess salt, but also if there is a nutrient imbalance. An imbalance most often forms if you water your plants with tap water. To fix this, you could buy distilled water for your plants.
Nutrient imbalances can also occur from overfertilizing or lack of nutrients – this is where the importance of research comes in!
To avoid nutrient issues, you could fertilize every spring with different fertilizers for houseplants.
Treatment Options for Pests
Many indoor pests can cause brown leaves, or necrosis, on plant leaves. If it is a pest you are dealing with, identify it and proceed to create a care plan for the plant.
Whether it is spider mites or fungal leaf spot, to treat the plant, you must first trim off all damaged leaves. If over 50% of the plant is damaged, you might want to consider tossing the plant for the greater good.
Once all dead and infected leaves are trimmed off with sanitized scissors, spray the plant with insecticidal soap or neem oil every other day until the plant begins to recover.
Make sure to fully dispose of all infested plant tissue so that the pest does not return. If you are dealing with a plant virus, there is no choice but to dispose of all infected plants.
Brown spots on leaves can be caused by common pests such as aphids (pictured above). Aphids have piercing mouth parts, can reproduce asexually, and can be found on both indoor and outdoor plants.
For outdoor plants, there are fewer options for treatment because they are influenced by the outside environment.
The best way to prevent brown spots on leaves for outdoor plants is to make sure that you plant the specimen in the correct conditions.
In terms of pests that develop on outdoor plants, there are numerous prevention and treatment options.
Common Causes of Browning on Outdoor Plants
- Drought (most common)
- Inadequate soil (soil texture, pH, salt content, nutrients)
Drought, dormancy, plant death, and sunburn can all cause brown spots on leaves on outdoor plants.
Drought and sunburn cause crispy brown leaf edges and can be fixed by providing irrigation, planting drought-tolerant plants, and providing shade for your plants.
Dormancy is most recognized by analyzing the time of year. The best way to know if the brown spots on leaves were caused by dormancy is to wait and see if your plant returns in the spring!
Dormancy causes brown spots on leaves, so if it is autumn and your plant looks like it’s dying, wait until spring to confirm complete death. You can usually tell that it is dormant if the brown spots are surrounded by red, yellow, or orange coloring.
Solutions for Inadequate Soil
Brown spots on leaves can develop on outdoor plants if they are not planted in sufficient soil conditions.
Outdoor soil and its texture can influence nutrients, pH, and salt content more than indoor plants, especially since there is more surface area and variable weather.
Pictured above is soil with adequate soil texture for outdoor plants. As you can see, the soil is not too rocky or red (acidic) and appears to have good drainage.
Before planting a landscape plant, you could research your soil type and the requirement of the plant to ensure success.
If you would want to improve your soil quality, you could add mulch or a soil conditioner before planting.
Getting your pH and nutrient content tested is also an option because universities and extension offices offer these services.
Testing, researching, and prepping your soil is a way to avoid brown spots on outdoor plant leaves.
You could check to see if your plant would become sunburnt or dried out before planting to avoid plant death as well.
Treatment Options for Pests
Outdoor plants tolerate more pests than indoor plants, so many outdoor plants can develop brown spots on their leaves.
Common outdoor pests that cause brown spots on leaves include:
- Anthracnose (fungus)
- Septoria leaf spot (fungus)
- Downy mildew (oomycete)
- Powdery mildew (fungus)
- Rusts (various types, fungi)
- Sooty mold (fungus)
- Snails and slugs
- Maple tar spot (fungus)
- Gypsy worms
- Fall webworms
Powdery mildew is a common pest (fungus) that causes necrosis on plant tissue. A common sign of this fungus is a white, powdery coating on the leaves (pictured above). This pest thrives in humid, moist conditions, and will attack indoor and outdoor plants.
It may help to refer to a guide to better identify your specific pest.
If you discover that a pest develops on your outdoor plants, prune off the dead material, rake up all infected material, and dispose of it.
Contact an extension office or certified agriculturalists to treat your plant, seeing that sometimes chemical treatment is needed or removal of the plant.
Usually, brown spots on outdoor plant leaves are common and don’t become severe.
For example, for over a decade, the sugar maples at my homestead have developed tar spot. Every year it clears up and it has not needed to be treated thus far.
In cases such as this, be sure you keep a close eye on your plants every season. Some pests can develop quickly, so it may be helpful to check your plants every week for signs and symptoms of potential pests.
Gypsy moths (shown above) are a common outdoor pest that causes brown spots on leaves. The caterpillar is identified by its blue and red dots and is an issue for trees and shrubs in the spring when they build their webs.
Prevention of Brown Spots on Leaves
For indoor plants, there are many proactive activities you could do to keep brown spots on leaves from forming:
- Research your plants to establish a correct watering schedule
- Check your humidity to prevent drying out
- Harden off your plants
- Switch between top watering and bottom watering to prevent salt burn
- Avoid using tap water with high mineral contents to water your plants
- Try to fertilize every spring
- Repot plants when needed
Depending on your plant, one way to prevent brown spots on leaves is to repot your specimen when needed. Many houseplants such as ZZ plants (pictured above), spider plants, and pothos will develop brown spots on their leaves if they become too rootbound.
To prevent brown spots on outdoor plant leaves, I find these tips and tricks to be helpful:
- Check your plants every week for abnormalities
- Avoid planting plant hosts and alternative plant hosts together (could cause diseases like cedar apple rust)
- Clear out infected material to prevent further infections
- Quarantine new outdoor plants for a week before installing them into your landscape
- Research your plants’ needs and your outdoor conditions before planting
When you see that your plant has developed brown spots on its leaves (pictured above), it can be frightening. Rest assured that most plants can be recovered and there are numerous prevention methods!
Frequently Asked Questions
Q: What causes brown spots on leaves?
A: Pests, nutrition issues, or unfavorable environmental factors could all cause brown spots on leaves for indoor or outdoor plants.
Q: How do I decide if I should just throw my plant away?
A: If you see brown spots on leaves, identify the cause. If it is a virus, infested with pests, or over 50% brown overall, dispose of the plant.
Q: Should I cut off the brown leaves on my plant?
A: Yes. Cutting off brown spots with sanitized scissors or pruners will allow the plant to focus its energy on recovering. If the leaves are brown, they are no longer photosynthesizing so they are of no use to the plant.
Q: What does a plant need when it has a brown spot?
A: It may need different sun, water, or nutrient needs, or it might be hosting a pest. It could help to research the potential issue and the exact symptoms and signs that your plant has.
Q: Do brown leaves indicate that my plant is going dormant?
A: It is a possibility. You could eliminate other potential causes first, and then consider the time of year and your plant species before deciding that it’s dormancy.
Jen is a master gardener, interior designer and home improvement expert. She has completed many home improvement, decor and remodeling projects with her family over the past 10 years on their 4,500 sf Victorian house. She is also a passionate farmer who keeps goats, chickens, turkeys cows and pigs on her farm, and an instructor for her community’s Organic and Sustainable Farming project.