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There is one thing we often do by accident with houseplants in winter, and in my sister’s case, it resulted in plant death when she tossed her plant out into the snow last week.

Overwatering kills houseplants.

The trouble is most gardeners like routines. “I’ll water on Tuesdays,” you think to yourself. Then you mark it on the calendar and water every Tuesday. And it works – in the summer.

The trouble in winter is the light, or lack thereof, during the season’s shorter days.

Short days mean less growing time for plants and less water needed. If the plant sits near a window, the cool air means even less water is needed. In the chill and low light of winter, most plants only need about half as much water as they needed in summer.

I water my Christmas cactus once a month in summer. The soil gets so crusty dry it almost looks like it is going to wilt. However, this tropical plant has fleshy leaves and it really doesn’t need a lot of soil moisture to thrive.

In the winter, I check my plant monthly but only water as needed. This general rule holds for philodendrons, citrus and dieffenbachia as well.

Water houseplants sparingly in winter. Otherwise, they might rot in soggy soil or slowly die from sitting in water.

If the excess water doesn’t kill your plants, a little black fly called a fungus gnat will eat the roots and finish it off. Gnats hatch when the soil is evenly moist for a long time. Adults emerge, mate and lay more eggs into the soft, moist soil.

This is exactly what happened to my sister’s plant. She overwatered her Christmas cactus, and when she went to add more water, the tiny black flies flew up into her face. Then she watered it again a few days later and more flies appeared. To eliminate her infestation, she threw the plant out into the snow.

This was completely unnecessary. All she needed to do was withhold water. A plant I got from the same source at the same time is currently sitting in my house dry as a bone. I will water it again when the soil is extremely dry.

Until then, I am saving my energy and my water. Because if overwatering doesn’t kill your houseplants, fungus gnats – or in my sister’s case, snow – surely will.