A hand waters a houseplant on a windowsill
(Image credit: Elena Zaretskaya / Getty Images)

Here at Gardening Know How we get lots of questions, and our goal is to provide answers to those inquiries to the best of our knowledge. For example, growing houseplants successfully means providing the best possible care. But even with great care, problems can and do arise from time to time. The following information includes the 10 most commonly asked questions about houseplant problems. 1. Why are my plant leaves turning yellow? Yellowing of leaves is one of the most common and hardest to solve problems when it comes to houseplants. This is because it's a symptom of lots of common houseplant complaints. The main culprits are usually not enough or too much light, or not enough or too much water. Try to assess if you're giving your plant too much or too little of something - is the soil almost always wet or almost always dry? You're probably over or under watering. Is the plant in a window that gets bright afternoon sun or tucked in a corner with no direct sun? It's probably getting too much or too little light. Try adjusting in a way that makes sense, and wait to see if the plant perks up. 2. How do you successfully overwinter plant indoors? Successful overwintering of houseplants really depends upon the type of plant you're dealing with. Some plants need to go dormant over the winter - this means possibly pruning it back and placing it somewhere dark and cool, like a basement or garage. Some other plants keep growing and need light throughout the winter - this means placing it by a bright window or even supplementing with grow lights. Plants often need less water indoors during winter, but they sometimes suffer from low humidity. You'll want to cut back on your watering routine but might want to mist the plant occasionally, or keep it above a dish of water. 3. Houseplant leaves are dropping. Why? Leaf drop on houseplants is another problem that can point to several different issues. One common culprit is a sudden change in environment. This includes temperature, light, and water, and it's often unavoidable when a plant is first brought indoors for the winter. If your plant drops leaves soon after it makes the move inside, don't panic. It's just adjusting and should recover. Some other causes include pests (like mealybugs, scale, and spider mites), over or underwatering, and lack of nutrients. Study your plant to see if anything has changed that might have caused the leaf drop. 4. What is the white furry stuff on plant? You're probably looking at an infestation of mealybugs or scale insects - they can look pretty similar. First, move your plant away from all of its neighbors to keep the infestation from spreading. Next, treat the plant with Neem oil. Neem oil is organic and safe for both plants and pets. Spray both sides of all the leaves once a week until the infestation goes away. You may want to lightly treat the plants that were next to the infested one, just in case any of the bugs travelled unnoticed. 5. What to do for sticky leaves on plants? Are the leaves of your houseplant sticky and shiny? Chances are the substance you're looking at is honeydew. Honeydew is a sign of an infestation of aphids, mealybugs, or scale insects. It's actually their"¦ excrement. The best way to get rid of these insects (and the stuff they leave behind) is with weekly sprayings of Neem oil, both on the leaves and in the soil. Ants often accompany honeydew - they love to eat the stuff. If you kill the bugs making the honeydew, the ants should go away, too. 6. What type of soil should I use for repotting? Most plants will be perfectly happy growing in regular potting soil. Depending upon the plant, you may want to add some organic matter, like compost, for extra nutrients and water retention, or some grit like sand or perlite for extra fast drainage. The stuff marketed as "garden soil" should be avoided, because it's very dense and doesn't drain well. This can result in wet, rotten roots for container plants. You should also avoid soil dug straight out of the ground, as it will also drain slowly and may harbor parasites and diseases you don't want to bring into your house. 7. Why do plant leaves turn brown? If your houseplant's leaves are turning brown, especially around the edges, then it's probably a sign of stress, most likely to do with not getting enough water. This could be due to a number of reasons. One likely cause is that the plant is root bound and the roots aren't able to take up enough water. This means it needs to be repotted. It's also possible that the plant isn't being watered enough, or that the soil isn't holding water well. The roots may also be suffering from tip burn due to too many salts in the soil (this can be fixed by flushing the pot with lots of water). 8. When do you water houseplants? The answer to this one really depends upon the specific plant you're growing. Succulents and cacti, for example, should be allowed to dry out between waterings. As a rule, however, most houseplants should not be allowed to dry out completely. That being said, the most common cause of houseplant death is overwatering, which is why watering properly is important. The surface of the soil is the part that dries out first, so testing it for dryness isn't always reliable. Try tapping on the side of the pot - if it sounds dull, there's probably still moisture in there. If it sounds hollow, it's probably dry. 9. How to eliminate mushrooms in houseplants? Mushrooms in houseplants are usually introduced as spores in contaminated potting mixes, but they can drift in through the air, too. They tend to grow in humid, moist conditions. To get rid of them, first remove the caps to keep more spores from spreading. If you can, scrape away and replace the top two inches of soil. Drench the remaining soil with fungicide - Neem oil is an effective and safe choice, especially if you have pets. Replacing all the soil and moving the plant to less humid conditions will also help. Getting rid of mushrooms is hard, but thankfully they're not usually harmful. 10. What causes water to drop from houseplant leaves? There's a chance that this is honeydew and a sign of pest infestation (see questions 4 and 5). It's more likely, however, that you're looking at guttation, a perfectly natural and harmless plant activity. To draw up nutrients and water through their roots, plants create a vacuum by allowing moisture to evaporate out of tiny holes in their leaves called stomata. When the air is humid, especially at night, less moisture evaporates. Instead, it forms tiny drops of condensation over the stomata on the tips of the leaves. We all have questions now and then, whether long-time gardeners or those just starting out. So if you have a gardening question, get a gardening answer. We're always here to help.

Liz Baessler
Senior Editor

The only child of a horticulturist and an English teacher, Liz Baessler was destined to become a gardening editor. She has been with Gardening Know how since 2015, and a Senior Editor since 2020. She holds a BA in English from Brandeis University and an MA in English from the University of Geneva, Switzerland. After years of gardening in containers and community garden plots, she finally has a backyard of her own, which she is systematically filling with vegetables and flowers.