By Beth Berlin
U of M Extension
Winter can be a harsh time for our houseplants; temperatures, dry conditions, pests, and lack of sunlight can all be stressful on them. With a little extra care, your houseplants can continue to thrive.
The first thing to address is light. At this point in the year, light is at a premium so it is important that our plants are clean and free of a dust layer so they can optimize all the light they receive to photosynthesize. Not only is the dust not attractive and filters the light from getting to the leaf tissue, but it also can encourage pests.
Cleaning your houseplants can be a bit of a chore. For large leaf plants such as your peace lily, you can wash by hand with a rag dipped in lukewarm water and a few drops of mild dish soap. For plants with tiny leaves you can quickly tip upside down into a tub of similar water. Wrap the top of the pot to prevent soil from dumping into the wash tub. Cacti should not be cleaned with a wet rag or dipped, simply dust off the plant with an old toothbrush.
While cleaning your plants, inspect them for pests such as insects or mites. Winter creates the perfect dry, warm conditions in our homes that several houseplant pests prefer. Inspect both tops and undersides of leaves, paying special attention to any leaves that appear mottled or speckled. Some insects leave other signs such as honeydew, a sticky, shiny substance which is secreted by aphids or other scale insects. Look for fine webbing which is left by spider mites. Most houseplant insects are hard to detect with the naked-eye so using a hand-held magnifying glass will provide additional assistance.
If insects are discovered, act immediately. Isolate the plant from the others and treat the infested plant. Wash off minor infestations on smooth leaved plants using a soft cloth and a mild soap solution containing ½ teaspoon mild dish soap that doesn’t contain degreaser and one quart of lukewarm water. If your plant has spider mites, you will need to wash using a product containing bifenthrin, an insecticidal soap, or plant oil extracts. If your plant is infested with scales or mealybugs, carefully remove them or look for products containing bifenthrin, permethrin, disulfoton, or imidacloprids.
Plants with heavily infestations may require multiple applications of an insecticide. Several ready-to-use insecticides in containers are available on the market. It is very important to read the label thoroughly to ensure both the plant and insect that you plan to treat are listed on the label. Also read the label carefully and follow all directions and precautions. If the plant is heavily infested it may be best to simply destroy the plant instead of using chemicals or providing more time for the infestation to spread to other plants.
Anytime you purchase or receive a new plant, be sure to isolate it from your other houseplants for a few weeks and inspect the plant closely for signs of pests. Once you have completed the isolation period and thoroughly inspected the plant, it can be located near your existing plants. Continue to monitor all plants throughout the year since there are several ways pests can enter into our homes.
Use these tips not only in the winter, but all year round to help ensure healthy houseplants. For more information on houseplant insects, infestation, prevention and treatment visit: www.extension.umn.edu/garden/insects/find/houseplant-insect-control/.