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Potting-soil fungus draws gnats


Little black insects are flying around my houseplants. They don't seem to be eating the plants, but I'd like to know what are they and if I should be concerned.

You are seeing fungus gnats -- annoying but harmless flies. They live and breed on the organic matter in your potting soil. They feed on the fungi that grow in moist soil.

Temporarily dry out the potting soil in the plant containers that they are congregating around. When the soil dries out, the larvae will die. Avoid over-watering houseplants to prevent the gnat problem in the future.

Last winter my evergreen shrubs suffered from the extreme, cold weather. I've heard of anti-desiccant products that can protect plants from winter burn. Do these work?

Anti-desiccants are made of beeswax or other materials. They are sprayed on shrubs to form a coating over foliage. The coating is designed to help the plants hold moisture. Unfortunately, anti-desiccants have limited effectiveness. The coating wears off and may have to be reapplied as many as three to four times over the winter. The culprits are sunlight and heat during warm spells, which break down anti-desiccants.

Furthermore, over-application of an anti-desiccant can cause burning of foliage.

If you decide to use an anti-desiccant, apply it only when the temperature is above freezing. That way you'll avoid trapping ice or water in the foliage. For best results with an anti-desiccant once winter is under way, wait a few days after the temperature rises above freezing to reapply.

You can protect your shrubs from winter winds by surrounding them with burlap or by constructing small, solid windbreaks about 18 inches from the shrubs on the windward side.

I just received a Christmas cactus as a gift. How should I care for it and how long will it bloom?

Keep your cactus in a bright spot but out of direct sunlight. Excessive light will turn the foliage yellow. Cactus grows well at average household temperatures, but, as a succulent, it needs constant moisture. Always keep the soil around your Christmas cactus moist.

Your cactus will bloom through the winter and perhaps into early spring. There is no need to fertilize a Christmas cactus over the winter months. Also, your plant can be set outdoors during the summer months and then brought back inside and forced to bloom in fall.

Garden tips are provided by the Home and Garden Information Center of the Cooperative Extension Service of the University of Maryland. For additional information on these questions or if you have questions of your own, call the center's hot line at (800) 342-2507.


Avoid the temptation to kill snakes that wander into your home during the cold months. In Central Maryland, there's virtually no chance you'll come upon a poisonous snake in your house. Instead, the usual trespassers are ring-neck and black-rat snakes. Both are harmless and both eat the field mice that can plague gardeners. Gently escort them outside or find someone else to do the job.

Review your 1996 garden diary to see what worked and what didn't work during the planting season. Jot down your observations so you can build on successes and avoid mistakes.

Drain water from garden hoses and store hoses indoors. Drain valves leading to outdoor spigots to avoid cracks in pipes caused by freezing.

Pub Date: 12/01/96

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