Garden Variety: Cleaning houseplants and other tips for winter care

Plants kept indoors, whether they are indoors all year long or only inside during winter, need care like any other plant. And even though temperatures change less indoors than they do out, there are changes in light intensity, light duration and humidity that can stress plants. As winter approaches, cleaning houseplants and making other adjustments will reduce stress to keep them shining through the season.

To clean houseplants, start by removing dead or damaged leaves and stems as they may be diseased and provide a source of inoculum for the rest of the plant. Spring is a better time to heavily prune or re-pot plants, but light pruning to remove unhealthy plant parts or slightly reduce the size is acceptable. Re-pot now only if necessary to optimize plant health.

Next, dust the leaves. If you enjoy cleaning, you may already do this regularly. If you spend spring and summer in the garden and cleaning goes by the wayside, plants may really need this now. Dust blocks light from plant cells and interferes with photosynthesis. This is more noticeable on plants with broad shiny leaves, but problematic on all plants.

Remove dust from smooth-leaved plants by gently wiping down the leaves and stems with a soft damp cloth. This works well on Chinese evergreens, Dracaenas, snake plants (Sansieviera), peace lilies, ZZ plants and other similar species.

For sensitive plants like African violets, use a dry paintbrush, feather duster or a very soft-bristled toothbrush to sweep the dust from leaves and stems. For less sensitive but tender or otherwise hard to clean plants such as cacti, succulents, small-leaved ivies and bonsai, rinse plants in the sink or shower. Use room-temperature or tepid water to avoid scalding or shocking plants. Let them drip dry before returning to their regular location.

There are products available in some garden centers and online that make plants look extra glossy after dusting and are generally referred to as leaf shine products. There are anecdotal reports for and against the products, claiming they are safe or that they clog plants’ pores. Research has yet to prove either. One known downside to leaf shine products is that they are a tiny bit sticky, so plants collect a little more dust than they would otherwise.

Even if your grandmother swore by wiping plants with milk, coconut oil, household cleaners, mayonnaise, banana peels, or other household items, none of these are recommended. These materials leave residue that blocks more light than the dust did, make leaves sticky and/or attract insects.

While cleaning, look for signs of insects. Scale insects may look like little hard or soft turtle shells attached to leaves and stems. When scraped, the insect (or many baby insects) is present under the shell with a sticky residue. Mealybugs are oval-shaped and white to gray with what looks like a fuzzy edge. They are mostly stationary on the plant like scale insects. Spider mites will be invisible to the naked eye on plant leaves, but can be seen by tapping leaves over a white sheet of paper. The mites will look like tiny moving dots. Light webbing from the mites may be noticeable on the undersides of plant leaves or occasionally on stems and buds. If insects or mites are found, treat or destroy plants as the insects or mites will only increase in numbers over the winter.

Also while cleaning, give the windows that plants reside in a good dusting as well. Dust can block light coming through the glass.

Cut back on watering plants until temperatures and daylength are both increasing. Instead of watering on a schedule, check soil moisture on a schedule. Check below the surface and only apply additional water if soil is dry. Then, water thoroughly – until water flows out the bottom of the pot. Remember that potting soil works like a sponge and can be hard to rewet if allowed to completely dry out.

Avoid fertilizing plants until temperatures and daylength are both increasing.

Move plants away from drafts and vents to avoid sudden temperature fluctuations.

— Jennifer Smith is a former horticulture extension agent for K-State Research and Extension and horticulturist for Lawrence Parks and Recreation.