WINTER CARE OF HOUSEPLANTS
by Jerry Parsons, Ph.D.
Horticulture Specialist, Texas Agricultural Extension Service in San Antonio

Now that the cold winds of winter have arrived, people are keeping their green thumbs in tune with care and culture of houseplants.

The custom of growing plants indoors is not a new one. At a very early date, man learned how to grow plants indoors during the long winter. These plants probably had culinary or medicinal uses. Gradually, man came to grow house plants simply for his own pleasure and enjoyment. Thousands of years ago, homes were decorated with pots, jars, and baskets containing living bits of nature.

Until about the middle of the eighteenth century, the indoor gardener had only a limited variety of houseplants from which to choose. Luckily, many rare and exotic species were discovered through world exploration. Today, many hundreds of species are available for indoor gardening.

The plants one chooses to grow should be readily adaptable to its new indoor environment. The more nearly the indoor conditions resemble the natural habitat of the plant, the better it will grow. The plants should be compatible with the existing decorating plan and act as room accents. Most importantly, select healthy plants.

Light is the source of energy for plant growth, so the amount and type of light available make it the first consideration in choosing a place for growing indoor plants. The length of the day has a great effect on metabolism - during the fall and winter when the days are shorter, most plants almost completely stop growing. Many homeowners who want to decorate with growing plants don't have adequate light in which to culture them. For those who want to try some houseplants in low lighting, choose those which will tolerate such conditions. These include the Chinese Evergreen, Spathyphyllum, Cast-iron plant, Maidenhair Fern and Birds-Nest-Fern.

In addition to the shortness of the days, another factor which contributes to the dormancy of many plants is the diminished intensity of light in the winter. Plants will not bloom unless the level of illumination is approximately that of their habitat, although they may survive and even grow quite well with considerably less light in many instances.

A southern exposure gets the most light and is usually the best location for most plants. An east window is the second choice because it receives the morning sunlight. A western exposure can support many plants but afternoon protection may be needed. A north window gets almost no directly sunlight, but a good variety of plants may still be grown if they are selected carefully.

Temperature is also an important environmental factor. Plants flourish much better at their natural temperature. In almost every house, there are wide differences in temperatures between rooms, and even between areas of the same rooms. For example, window sills are almost always cooler at night than the center of the room.

Humidity is the third important factor to consider when growing plants indoors. The natural habitat of a plant may have been very humid or very dry or somewhere in between. The air in most homes is usually too dry in winter to support many types of plants except succulents. The gardener must then provide the additional humidity that the plants require.

There are several ways to increase the humidity around houseplants: misting with lukewarm water, placing a tray of water near the plants, and grouping plants close together so that their combined transpiration will raise the humidity around them.

The quality of the soil that the plants will grow in is vital. Most plants grow well in the packaged commercial soil mixes. Be sure to choose one that is high in organic material and has been sterilized to kill insects, diseases, and weed seeds.

The correct container is also important. The height or diameter of the container should be from one-fourth the height or width of the plant. Unglazed clay pots with drainage holes are usually the best types to use because they lessen the chances of overwatering.

The steps in potting a plant are simple, but it is vital to the future plant to follow them carefully. A plant needs repotting when a mass of roots develops that presses against the wall of the pot. To remove a plant, hold the root ball with your hand, turn the pot upside down, tap the pot sharply, and the plant will slide out. The job is much easier if the plant was watered thoroughly the night before repotting. Place the plant in a pot one-half to one inch larger than the previous pot. Fill the soil in gently around the tender roots.

Of all the factors in the natural environment of a plant, the most difficult to reproduce is the moisture content of the soil. The amount of water a plant needs usually depends on the temperature of the room, the kind of pot, and the size of the plant. Be sure to soak the soil thoroughly so that every particle is wet. Then, when the excess water drains away, the soil will be uniformly damp and the roots can use all of the available space. The best way to determine how much moisture is in the earth is to touch it with your finger. Avoid overwatering -the soil should be slightly dry before the plant is watered again.

There are many easy to grow houseplants - for instance Chinese evergreen, Cast-iron plant, Maidenhair Fern, Birds-Nest-Fern, Sansevieria, Philodendron, Pothos, Spathiphyllum and Zebrina to name a few that can be used. Some of the most dramatic houseplants, however, are the various species of palms. The Lady Palm (Rhapis excelsa) is a palm that can be used outdoors in the shade and its shade tolerance also makes it an excellent indoor palm. It's rather slow growing and large specimens can be expensive, but it is a beautiful palm well adapted to indoor conditions. The Pigmy Date Palm (Phoenix roebeleneii) is often used as an indoor palm and unlike its huge relative that produces the commercial dates it is more adapted to home conditions. Fountain Palm (Livistonia chinensis) is a palm that will grow in protected locations outdoors here and has huge, bright-green fan-type leaves. It would be an excellent plant to use in an atrium. The European Fan Palm (Chamaerops humilis) is quite hardy outdoors going as far north even as central Texas, but it can make an excellent indoor palm as well. With age it tends to form multiple trunks in cluster fashion. One of the best of the indoor palms available on most seed racks and is the best to use for ornamental use since it produces several blooms with much better than some other palms, especially the often sold Areca Palm.

There are many good houseplant fertilizers on the market. Frequent fertilizing is necessary because the soil rapidly loses many of its nutrients through frequent watering. However, overdoses of these fertilizers can cause weak stems, lanky growth, and even death. Read the label and follow the directions! Don't overdo the fertilizers! In fact, if the light intensity is low, it would be best not to fertilize from October 15 until March 15.

By providing the correct natural environment including light, temperature, and humidity and by careful potting, watering and fertilizing, you can grow beautiful healthy plants. Finally, some of the few good imitations of real plants have been several of the artificial palms. If your thumb isn't the least bit green, or if you need a plant for a dark hallway, these might be permissible.

For more information about many types of houseplants and pictures of each, see:

http://aggie-horticulture.tamu.edu/interiorscape/indexcommon.html