All houseplants need a certain amount of light each day for growth, the amount varying with different plants. Some plants need full sunlight—day-long exposure to the sun—while some require only partial sunlight. Flowering plants require sunshine for the development of buds, and plants with colored leaves need it to retain their bright colors. Most foliage plants, on the other hand, grow well in indirect light or shade.

Houseplants are usually kept near windows to give them the best possible exposure to light. Generally, windows facing south receive full sunlight during the day, and east and west windows receive partial sunlight—that is, sunlight during the morning or afternoon only. Some of the plants that do well in full sunlight are azaleas, cacti, geraniums, and the shrimp plant. Such plants as African violets, begonias, and coleus grow better in partial sunlight. Many green-leaved, non-flowering plants—such as Chinese evergreen, ivies, philodendrons, and the rubber plant—will grow well in the shade or in north windows, which receive indirect light.

Certain houseplants can grow well in basements and other areas without natural light if placed under a combination of fluorescent and incandescent light for 14 to 16 hours a day. However, maintaining the proper temperature and humidity in these areas is often difficult.

Most house-plants grow best at temperatures between 60° and 70° F (16° and 22° C). Fresh air is good for plants, but they should not be exposed to sudden changes in temperature. Cold drafts from open windows and doors, as well as excessive heat from radiators, can harm them.

Almost all plants grow better in an environment of high (5O to 60 per cent) humidity. Since most heated homes become rather dry in winter, some steps can be taken to provide additional humidity for plants. One way is to spray the plant's foliage once a day with a fine mist of water. Another way is to place a potted plant atop pebbles contained in a saucer filled with water. As the water evaporates, vapor will rise to the leaves of the plant.

Houseplants can die from over-watering as well as from under-watering. Too much water will cause a plant's roots to rot; when this happens there is little chance of reviving the plant. The lower leaves of an overwatered plant fade and drop off, while a plant given too little water will have a noticeable droop in its leaves and stems. A good rule to follow is to water plants when the soil appears grayish and feels dry when rubbed between the fingers.

Once the soil is ready for water, it should be completely soaked. When the plant is watered from the top, excess water will seep out through the drainage hole in the bottom of the pot. It should be collected in a saucer or other container, which should be emptied as soon as the seepage stops; a watered plant should not continue to sit in water.

A plant can also be watered from the bottom; this is done by continually filling a saucer underneath until no more water is taken up into the pot. A third watering method is possible when clay pots are used. Clay is porous and easily absorbs moisture, so the plant can be watered by soaking the pot in a container of water filled to about one inch (2.5 cm) from the rim of the pot. The pot should be removed from the water when the surface soil becomes moist.

Most houseplants will do well in a potting soil mixture of equal parts of builder's sand, peat or sphagnum moss, and loam (topsoil). Builder's sand is coarser than beach sand and promotes better drainage of water. Peat and chopped sphagnum moss are fibrous vegetable materials that absorb water and keep the soil moist. Loam contains plant nutrients and provides the weight and body needed to support the plant and hold it upright.

The nutrients in the small amount of soil in which potted plants live are continually absorbed by the plant or washed away by waterings. Therefore houseplants need feedings about every two weeks with ordinary garden fertilizer or commercially prepared plant food. Commercial plant foods are available in liquid, powdered, granulated, or tablet form. All plant foods contain three primary ingredients—nitrogen for the healthy growth of leaves and shoots; phosphorus for the development of flowers, fruits, and seeds; and potassium for strengthening stems.

Newly potted or purchased plants should not be fed for at least six weeks, nor should plants be fed during their dormant periods. Most plants become dormant between October and March; during this time they stop producing new growth and do not benefit from feedings. Plant food should be given sparingly because too much will burn the roots. Watering a plant just before feeding will protect the roots from the chance of being harmed by too strong a concentration of fertilizer.