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Winter care for houseplants

November 5, 2008
By Richard Gast, Franklin County Cornell Cooperative Extension

Although taking plants from the wild and bringing them indoors would seem to defy all things natural, evidence of wild plants being successfully cultivated indoors can be found in writings dating back to ancient Egypt.

Many modern-day gardeners, with their ability to manipulate in-home

environments and control the amount of water and nutrition offered to plants, have made houseplants an essential part of their homes winter

decor. In fact, raising houseplants, by some accounts, continues to be one

of North America's fastest growing indoor hobbies.

Successful cultivation and care of houseplants doesn't have to be complicated, but success cannot be achieved unless the plants you start

with are healthy and free of pests. And even the healthiest plants will

not survive unless they are given the amounts of humidity, water, fertilizer and light that they require.

Most houseplants will grow adequately at temperatures of 65 to 75 degrees. Cooler nighttime temperatures may further stimulate growth, thereby improving the health of many foliage plants and extending the beauty of certain flowering plants. This does not hold true for all plants, however. African violets, for example, may suffer if temperatures fall below 60 degrees for a prolonged period of time.

Houseplants generally do best with a southerly exposure, although plants that normally do not need direct sunlight usually do well in east-facing windows.

Keep in mind that plants will not grow or bloom as they should unless the amount of light they receive is similar to that found in their native environment. In fact, availability of natural light may well be the indoor gardener's most important consideration. Symptoms of insufficient light include small leaves, long, thin stems and a lighter than normal color.

In most cases, unless you can provide supplementary light, it is best to

select plants that require medium to low light. Keep in mind, too, that

plants receiving light from a window may need to be turned from time to

time, and that keeping foliage clean will allow plants to take full advantage of the amount of light that is available to them.

By cleaning houseplants, you also improve their appearance, stimulate growth and help control insects and mites. Always wash foliage with a soft cloth or sponge, using a very mild solution of (insecticidal) soap and room temperature to lukewarm water. Avoid washing hairy surfaced plants like African violets and begonias.

Be aware that plants grown on cool windowsills may be exposed to cold drafts or sudden freezing conditions. Some may suffer injury after just a few seconds of exposure. And since most plants will not tolerate hot air blowing on them, indoor gardeners should avoid placing plants next to or over heating ducts.

Almost all plants native to temperate or subtropical environments require relative humidity levels of about 40 to 50 percent. This is also a preferred relative humidity level for human health. Many tropical plants will adapt to this humidity level, but there are those that demand much higher relative humidity.

During winter months, relative humidity levels in homes can be as low as 10 percent. Almost all plants, other than desert plants, will wilt when exposed to such low humidity for prolonged periods, even when the soil they are growing in contains adequate moisture. Humidity levels in a home or a room can be increased by using a humidifier or by setting a pan of water on a radiator or wood stove. High humidity areas such as bathrooms and kitchens are often ideal for indoor plants.

Although misting will temporarily raise humidity levels, the added

moisture will evaporate quickly and minerals in tap water may cause

unsightly water spots to appear on foliage.

What's more, many indoor

gardeners will argue that misting sets the stage for fungal and bacterial

leaf spot diseases. If you do mist, bear in mind that softened water

should never be used, that chlorinated water should be allowed to sit

overnight before it is used in misting or watering, and that some plants

are quite sensitive to fluorides.

Houseplants need to be watered thoroughly. Water should always be room temperature and soils should be allowed to dry between waterings. Excess water should be able to drain and should be immediately removed. They must never be allowed to sit in standing water.

Also, never assume that a wilting plant needs water. When soils become saturated roots can rot, which can cause wilting and eventual death.

Most gardeners agree that houseplants need very little or no fertilizer at all during winter months. Those that do feed their plants use dilute

solutions of complete and balanced water soluble fertilizers and they keep feeding to a minimum. The idea is just to maintain the plants until longer days and warmer conditions return.

For plant-specific information, contact me at Cornell Cooperative

Extension of Franklin County and ask for the fact sheet "Light,

Temperature, Water, and Other Basic Information for 50 Common




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