Garden Variety: Keep your houseplants from stressing out this winter
Winter is a tough time for houseplants, even when they are kept in the temperature-controlled environment of a home or office. Short days, reduced light intensity, dry air, exposure to drafts and other seasonal factors reduce the rate at which plants photosynthesize and create a less favorable growing environment. When combined with other stresses such as being potbound or fighting an insect infestation, these factors can be detrimental. Here are ways to keep your plants healthy through the winter months.
Light is always the most important thing for plants. The amount of light required to survive varies with species, but almost all plants need to be near a window at a minimum. Plants that grow well in a north or east window during most of the year may even need to be moved to a south or west window for a few months in the winter. Plants that prefer a sunny window or to spend the summer outdoors may simply show stress throughout the winter months.
Determining how much light a houseplant needs may take a little trial and error. Knowing the plant species helps to start. Then, as a general rule, if a plant is spindly and stretching toward a light source, it needs brighter light. If leaves begin to scorch and appear faded, the plant may benefit from being moved to an area with less light.
Watch for drafty windows or locations near doors where plants are exposed to very cold breezes and frosty temperatures. Most houseplants are tropical and cannot tolerate the very low temperatures of Kansas winters. If plants are in drafty locations, move them.
Plants tend to collect more dust in the winter, which can further reduce photosynthetic activity. Wipe dust from plants with a damp cloth or sponge, or place them in the shower and rinse the foliage periodically.
Since plants are photosynthesizing less in the winter than they do in other months, they also need less water. Overwatering is one of the most common stress factors for houseplants, and plant owners are most likely to overwater in the winter because they forget to adjust application rates. Always check soil moisture below the surface before watering. Also, water plants thoroughly (until water drains from the bottom) each time. This ensures even distribution of water through the potting soil and encourages deep root growth.
If plants are receiving proper amounts of light and water but still seem stressed, check the roots. Remove the plant from the pot. If roots at the bottom are wrapping around the inside of the pot (or trying to grow out of it), the plant is potbound and needs to be re-potted. There are two options: trim the roots and reuse the pot, or use a new pot that is slightly larger in diameter. Either way, trim any roots that are circling around or completely meshed together to encourage new root growth.
Houseplants should always be potted with high-quality potting mix (also called potting soil and media) rather than garden soil. Potting mixes are designed to provide proper drainage and air space for the roots of tropical plants. Certain plants, such as African violets, orchids, cacti and succulents, may require or grow better in additionally specialized potting mixes.
Insect pests are another thing to watch out for. Spider mites, mealybugs and insect scales are common houseplant pests that are difficult to detect. If plants seem stressed, look very closely at the undersides of leaves, on the stems and in the points where leaves attach to stems for insects and signs of insects. To check for spider mites, shake a few leaves over a piece of white paper and look for tiny moving specks on the paper. If insects or mites are detected, seek treatment for the specific pest.
Dry air is often a stress factor, but little can be done to remedy it. A humidifier helps some. Grouping plants and/or placing trays of water under or around houseplants are often recommended, but research shows no benefit from these practices.
Avoid fertilizing houseplants in winter as plants are not actively growing and taking up nutrients. Resume fertilization when plants begin growing again in late winter or early spring.
— Jennifer Smith works in regulatory horticulture and has worked as a horticulturist for various government entities. She has experience in landscape design and maintenance and as an educator.