Houseplants bring life and color into our homes. When they thrive, they are incredibly rewarding, but when they inexplicably start to wilt and die, they are nothing short of exasperating. What you may not know is that houseplants are prone to a variety of diseases and problems, and by learning to identify them, you can get to the root of the cause and get your plant back on track.
Most houseplant problems fall into three categories: environmental factors, pests, and diseases. The symptoms of each are fairly similar, so it might take a little detective work to figure out which suspect is the culprit.
While it might seem logical to assume that a pest or disease is attacking your plant, often the answer is much simpler. Environmental factors like light, nutrition, and watering play a huge role in your plant’s health and immune system.
Inadequate lighting, or in some cases, too much light, can cause symptoms similar to those caused by pests and diseases. If your plant is spindly, produces few flowers, has yellowing leaves, appears weak, or loses leaves, then it might not be getting enough light. If the leaves have a scorched appearance, then your plant might be receiving a little too much.
Plants need food, but fertilizers can cause problems if not applied properly. If your plant has very green leaves and is growing well but not putting out any flowers, you are probably using a fertilizer too high in nitrogen. If the tips of your leaves turn brown, you might have a fertilizer or pesticide burn, also caused by an excess of nitrogen. On the other hand, failure to fertilize can result in poor growth, so follow the directions on your product carefully.
The biggest issue most houseplant owners struggle with is water. Some gardeners overwater out of kindness, while others practice benign neglect, leaving plants to struggle through dry spells. Inadequate watering can also cause disease and weaken the plant’s immune system, exposing them to pests, so pay attention to the water requirements of your plant.
Overwatering results in yellowing leaves, especially if the soil drains poorly. It can also result in weak growth, small leaves, wilting, and defoliation. Underwatering can also cause small leaves, wilting, and brown leaf tips.
Temperature is another environmental factor that often goes unnoticed. We tend to assume that houseplants are safe indoors, but window sills can get cold at night, especially for tropical plants. Low temperatures can cause defoliation, brown leaf tips, and yellowing leaves, so make sure you rule out this problem as you troubleshoot.
Common Houseplant Pests
You might think that because your plants are indoors, you’ve escaped the perils of pests. Unfortunately, this is not the case. Houseplants are prone to a variety of pests, including aphids, mealybugs, mites, scale, thrips, and whiteflies.
Aphids are tiny insects that cluster on the undersides of leaves. They can be green, brown, or black in color, and their feeding habits stunt growth and result in distorted or curled leaves.
These bugs are a species of sap-sucking scale insect. They create a white, cottony appearance on houseplants, and cluster on the undersides of leaves and on plant nodes.
These tiny spiders are usually light in color and create webs on the stems and leaves of plants. Their feeding habits create yellowish, distorted foliage.
Scale insects suck the sap out of plants, leading to stunted plant growth. There are many species of these bugs, so look out for either round or oval-shaped brown insects on the stems and leaves of your plant.
These pests feed on leaves and flowers, discoloring and distorting them. It might be hard to see them as they are extremely tiny, but if you can, look for tan or brown-colored specks. Thrips are whitish when young, but are not to be confused with whiteflies.
Whiteflies are—unsurprisingly—white, gnat-like insects that feed on plant leaves. They will turn leaves pale yellow or even white in heavy infestations.
Once you have identified your specific pest, do a little research into proper removal. Depending on your preference, there are natural, organic, and chemical pesticides available.
Common Houseplant Diseases
Houseplant diseases typically stem from overwatering. Water creates moist environments for bacteria and fungi to thrive, which is bad news for your plants. The most common houseplant diseases are anthracnose, root rot, leaf spots, and powdery mildew.
This is a fungal disease that turns leaf tips first yellow, then brown, and can ultimately kill the entire leaf. If you suspect anthracnose, remove the infected leaves and avoid getting water on other foliage in the future.
Root rot and stem rot, much like their names imply, are diseases that cause the roots or a stem of a plant to rot, resulting in wilt and plant death. Treating root rot is tricky; in some cases, you might be able to cut away the infected roots and repot the plant in sterile potting mix and a clean pot, but the best option is to remove the infected plant entirely and avoid overwatering in the future.
Leaf spots can be either fungal or bacterial. Fungal leaf spots are brown with a yellow halo while bacterial spots look water soaked with a yellow halo. Increasing air circulation, removing infected leaves, and keeping leaves dry when watering can help correct this.
A fungal disease that results from poor air circulation, powdery mildew is easy to identify, as it looks exactly like its name — a powdery layer of white mildew covering the leaves. Powdery mildew can be avoided by increasing the air circulation around the plant, removing infected leaves, and avoiding overwatering.
These are the most common problems you'll encounter with houseplants, but that does not mean they are the only things you will see over the course of your career as a gardener. It is also important to remember that it can take a new plant a little while to adjust to the conditions in your home, so don't panic if your plant takes a few weeks to perk up.