by Diane Sagers

CORRESPONDENT

With very cold weather the order of the day outside, it is time to focus on gardening inside. We are not referring to those silk plants that grace so many homes these days. While they are attractive and care is painless -- requiring only a little dusting from time to time -- healthy plants growing indoors carry a peaceful charm and elegance.

We call them houseplants but that designation is a misnomer. All plants have natural habitats -- areas where they grow naturally -- and none of them grow naturally indoors. Plants are not houseplants, but are outdoor plants. However, with the right care, real plants will adapt to indoor conditions.

Try to identify and correct the differences between the home environment and the plant's natural environment.

Home conditions include a dry atmosphere and very low light. Those are two of the most important limiting factors for plants. Temperatures may not be just what the plants prefer, either.

Fortunately, you can alter the environment to a point, and plants are also somewhat adaptable. The trick to successfully raising robust plants indoors is to choose plants for which you can create a friendly habitat. Figure out what the plant needs and try to create those conditions in your home.

Most of the plants we try to grow indoors grow naturally in tropical environments. They like the warm temperatures of houses and adapt to lower light conditions, but humidity is always a problem.

With furnaces belching warm air through forced air heating, home humidity is something like that of the Sahara Desert. Humidity is very low -- often in the range of about 3 percent.

Resolving that problem is important but not simple. People have come up with an assortment of "fix-its" that are something less than effective. A spray bottle or misting bottle sounds like a good plan, but the very dry air throughout the room quickly absorbs the extra moisture.

The easiest solution is to grow plants in groupings. As plants in the groups transpire, they create some humidity around them. A group of them tend to support each other.

Pebble trays are also easy to make and use. Fill a tray or low dish with pebbles. Add water nearly to the top of the pebbles. Sit a pot on top of the pebbles making sure that it does not rest in the water. As water evaporates from the pebble tray, it creates a pocket of humidity around the houseplant. A room humidifier is also beneficial for plants.

The tropical environment our plants are naturally adapted to consists of an overhead canopy of dense foliage that shields the sun. However, the light naturally in houses is often less than that. You can adjust light conditions for a plant by placing it carefully. Direct light through a south window is usually too strong for tropical house plants. Except during the dark winter months, even diffused light through a curtained south window can be too strong. A curtained east or west window would probably provide enough light for most plants. A north window or no window probably will be too dark and plants grow long and gangly between the leaves.

Water is a critical factor in houseplant care. Everyone knows the tropics are wet with annual rainfalls that are way off the charts. However, that does not translate to wet soils for the plants. House plants are far more likely to be overwatered than underwatered.

Drainage is critical. In natural soil, water tends to drain through the soil, drawing air down to the roots in the process. Confining roots to a small pot means water cannot drain as easily. Drainage is the key to watering.

Pots should never stand in water. Many times people want a formula for watering. Water when the plants need it. In most cases, houseplants should be watered when the surface of the soil is dry to the touch. However, it should never dry throughout the root ball unless you are raising desert plants. The pot should be moist to about a half-inch of the surface of a 6-inch pot.

Water thoroughly enough that it completely penetrates the pot and drains through the bottom. Be sure to empty trays containing water that drain through the holes in the bottom of the pot. Standing water promotes root rot by cutting off oxygen. Roots do require water to grow, but they also require air. As much as water draining from a straw pulls air behind it, air follows water through the potting soil structure as it drains.

Proper potting soil is also a critical factor for plant growth. While many plants grow well in the garden where water has wide expanses to drain away, garden soil is too heavy for potting plants. Water stands in the soil and the soil hardens as it dries, further cutting off water.

A good soil mix should include a sterile combination of humus for water retention, sand for permeability and the addition of peat moss to make the soil mixture light and spongy.

Some potting mixtures contain no soil, but consist of components like peat moss, perlite, vermiculite, bark or sand. Many of these support plant growth exceptionally well. A wide assortment of potting mixtures are on the market, and some are better than others, but blacker isn't necessarily better. Government regulations do not cover soil labeling. Anything can be listed as "potting soil," so quality is not standard.

If you haven't settled on a favorite mixture, ask for a sack of whatever your favorite nursery uses.

Plants should be re-potted, generally in the spring, when they outgrow their pots. Roots need room to expand as plants grow larger.

Unfortunately, when you create the ideal environment for plants to grow, you also create ideal conditions for plant pests to thrive. Pest control can be a concern, but healthy plants are less susceptible to pests than those on life support.

Take care of the general concerns of sunlight, soil type, water, temperature and humidity to avoid a lot of problems.

Check plants periodically for insects and other pests to catch them before they severely damage the plants. Cleanliness also helps prevent pest attacks. Keep plants clean by dusting or washing leaves, removing damaged foliage and faded flowers, and sterilizing pots when re-potting.