Extending Notes
Houseplant Care in Winter

Winter can be a time of stress for houseplants from many causes. I wanted to mention some stresses on plants that are fairly common.

It is normal for plants to be taken outside during the warmer weather, then brought indoors to get through the cooler season. In our area, it is during that indoor visit that most plants have the most difficulty. They are adjusting to substantially decreased light and low humidity if they are kept inside your house. Any additional stresses at that point can cause problems that are obvious. During the summer strong sunlight and long day lengths encourage vigorous new growth and problems are less noticeable.

Last week we talked about the effects of various de-icing compounds, including road salt, on landscape plants. Well, houseplants can also be affected by salt. .

If you use softened water for your houseplants, that water adds sodium to their diet, and to the soil. Water softeners work by replacing the calcium and magnesium in the water, often with sodium.

Calcium and magnesium compounds are the components that make water hard, leading to lime deposits on plumbing and making it hard for soaps to develop a lather. They are important nutrients for plants though, and sodium is not. Softened water can also affect the soil structure for a potted plant, just as too much road salt can affect the soil structure of the nearby soil.

The sodium compounds accumulate in the soil of the houseplant, and can cause problems for the plant. Different plants have different sensitivities to sodium itself, but sodium can also affect the soil. With a few simple remedies the problem can be solved.

First, if there is a source of unsoftened water, use that water for your plants. Rainwater is a good source of water for this purpose. If you have a faucet in your water line before the water softener, you can also use that tap as the source of unsoftened water for your plants. If you have been using softened water, flush the soil with a good watering of unsoftened water, letting the unsoftened water rinse out the sodium from the soil medium.

Be sure the plants are well drained. If you must use softened water even occasionally, be sure that the roots of the plant and the soil around the roots are not soaked with the water. While soaking roots is never a good thing, it is especially bad with high levels of sodium in the water. Using a bed of gravel or other good drainage material under the plant will help keep the roots from remaining soaked. Good drainage will also slow down the degradation of the soil structure that comes from the addition of sodium.

If there has been a lot of accumulation of sodium salts, re-pot the plant in new potting medium. Soils with excess sodium will lose their normally crumbly texture and be hard when dry. Replacing that soil with fresh soil will give the roots of the plant a much better opportunity to reach nutrients.

Other chemicals in drinking water can also affect plants. Chlorine and flouride are two chemicals used in municipal drinking water systems to protect the health of the people using the water. Neither is beneficial for houseplants, though.

If you have chlorine in your tap water, draw the water and leave it out overnight before using it to water plants. You can also collect rainwater or use some other source of water that is not chlorinated. Heating will also eliminate chlorine, as will aeration. The chlorine coming out of the water will have a noticeable aroma. When that aroma has left the water, it can be used on plants. Just be sure that if you heated the water, it is cool again.

Fluoride is also used in some water systems to prevent tooth decay. Some house plants, especially spider plants, are sensitive to fluorine. If you have fluorine in your water, add a couple of teaspoons of powdered limestone for each quart of potting soil in each potted plant. The limestone will raise the pH of the soil, making the fluoride less available to the plants, thereby less harmful.

With a few precautions, your house plants will be much more likely to survive the winter, and remain healthy and ready to flourish when they go out in the spring.

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