Houseplants are a pleasant addition to your indoor living environment, especially through the winter.
A few types will flower in winter, bringing welcome spots of color during a dreary time of year. But you have many more choices with foliage plants, those that are native to tropical climates and produce lots of lush leaves in different shapes, color patterns and growth habits.
There are houseplants that need sunny windows, and those that tolerate lower light conditions. Some are tricky to grow and take a lot of care, while others are virtually indestructible.
But one problem we hear about this time of year that can be brought on by any kind of houseplant is fungus gnats. They're not a serious problem, but they can be quite a nuisance, and they're usually a sign that you are not watering your plants properly. They do not bite or get into our food.
Fungus gnats are little fly-like insects, dark in color. The adults can be seen flying around infested houseplants, but it's their larvae that do the damage. Fungus gnats lay their eggs in potting mix, and the small, white larvae feed on decaying organic matter, such as peat moss and bark, in the soil. They become a problem when their numbers increase to the point that the larvae begin feeding on the plant roots as well. When this happens, you may be able to see the white larvae squirming in the puddle that forms when you first add water. As the water soaks in, the larvae return to below the surface.
The best way to deal with fungus gnats is to try to avoid their build-up in the first place; this means not keeping the potting mix too damp. Let the soil dry somewhat between waterings; depending on the plant, you can let it become quite dry. Problems not only with fungus gnats, but also root rot, arise when the soil is kept constantly moist. When in doubt, wait longer between waterings.
When an infestation breaks out, begin by re-potting the plants. Shake the excess soil off the root ball, and re-pot with fresh, good-quality potting mix. Evaluate your watering practices, and vow to water less often.
Yellow sticky cards will trap some of the adults and are most effective when laid flat on the rim of the pot, rather than vertically on a stake as they are usually used. You can make your own sticky cards by smearing a thick layer of petroleum jelly on a bright yellow note card or the yellow Styrofoam trays commonly used for packaging meat.
To trap the larvae, use pieces of raw potatoes. Dr. Richard Lindguist from Ohio State University's Department of Entomology suggests two methods. Cut the potatoes into 1-inch-thick slices about 1 inch in diameter. Press the pieces into the surface of the potting mix, and leave in place for 48 to 72 hours. The other way is to cut the potato into "French fry" shaped pieces, which allows you to insert them deeper into the soil. Either way, check the pieces every couple of days, and if you find larvae tunnels in the potato, discard it, and replace with a fresh piece.
For more information and an illustration of fungus gnats, visit http://ohioline.osu.edu/hyg-fact/2000/2114.html. And you can always drop off a sample at our office any time for a free identification and information.
Amy Ivy is executive director of Cornell Cooperative Extension, Clinton County. Office phone numbers: Clinton County, 561-7450, Essex County, 962-4810, Franklin County, 483-7403. Website: www.cce.cornell.edu/ecgardening. Email questions to askMG@cornell.edu.