Black or brown spots on your plant - what does it mean?
Want to learn more about Symptoms: Black/brown spots
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Why are there black or brown spots on my plant?
There can be a number of reasons why brown or black spots appear on your plant. It’s a good idea to try and narrow down what could be the causing the spots on your particular plant. You can narrow down the possible issues by looking at the shape and color of the spots as well as where and how they are appearing on the leaves.
Signs
Dry brownish spots
Red or yellow zone along the edge
Mushy and discolored roots
Common causes
Causes can include cold draft combined with too much water, sunburn due to excessive light exposure, overwatering/lack of drainage, insufficient lighting conditions or underwatering. Additionally, keep in mind that variegated leaves (leaves that have more than one color) are more sensitive, meaning that the lighter colored parts of the leaves can become spotted and/or easily turn black or brown due to their sensitivity. Brown spots can also be caused by a bacterial or fungal infection known as Leaf Spot Disease.
If you’re finding it tricky to determine the cause of spots on your plant, the process of elimination can help you narrow it down. Check on your watering schedule to make sure that you’re not watering too often or too infrequently, and keep an eye out for additional symptoms. For instance, if you suspect that the cause could be overwatering/poor drainage, you can take a look at your plant’s roots - if they’re discolored or mushy then it could be a sign of root rot caused by too much water.
What to think about
If the spots appear in sunny or dry conditions
If your plant’s leaves have dry brownish spots, often accompanied by scorched leaf tips or sometimes pale leaves, it’s likely that it is being exposed to too much direct sunlight. This can be quite harsh for houseplants— particularly sensitive tropical plants that would naturally grow in the rainforest, where they’re protected from sunlight by forest foliage. Even species that can tolerate a lot of direct sunlight can get burnt if the plant isn’t slowly acclimated to it. To reduce the chances of your plant being sunburned, begin by placing your plant in a bright area out of direct sun and then slowly adjust it to more light.
Dry spots and leaf edges can also appear in lower humidity or if they’re placed over a heater/radiator that dehydrates the leaf faster than it can absorb water from the roots.
If the spots have a red or yellow zone along the edge
This is most likely a fungal or bacterial infection, which may have arisen due to high humidity and still air— often occuring in combination with overwatering and/or poor drainage. Fungal spots can vary in size, shape, and color just as bacterial spots and they can be hard to tell apart. If left untreated, it can progress to developing a hole in the leaf. Bacteria mainly spread by touching affected leaves and then handling other plants. It may also spread by water droplets hitting affected leaves, scattering them. Fungi can spread in a similar fashion or by sending out spores.