Several types of pots are commonly used for houseplants—the clay pot, the glazed pot, and the plastic pot. Clay pots are porous, permitting the soaking method of watering, but allowing the soil to dry out faster in heated rooms. Glazed ceramic and plastic pots are nonporous and tend to hold moisture longer under such conditions. No matter which pot is used it should have one or more drainage holes in the bottom; without proper drainage, plants will not live long.

Houseplants need repotting when they become top-heavy in their pots; when their roots become a crowded, tangled mass (an indication of this is when new leaves grow smaller and farther apart than normal); or when the roots begin to grow out of the drainage hole. The plant is removed for repotting by placing the stem (or stems) between spread fingers, turning the pot upside down, and gently rapping the sides of the pot against the edge of a table or bench to loosen the plant from the pot. If the plant's roots are tightly matted, they can be gently loosened with the fingers.

The new pot should be about one inch (2.5 cm) larger in diameter than the old one. The drainage holes should be covered with shards (broken pieces of pottery) and these covered with gravel or small pebbles. Next, a thin layer of sphagnum moss should be added to prevent the potting soil above from washing into the gravel layer and out of the pot. Enough potting soil should be added so that when the plant is centered on top of the soil, the beginning of its stern comes to about 3/4 of an inch (2 cm) below the top of the pot. (The empty space at the top prevents overflow when watering.) More soil is then added so that the roots are completely covered. The plant should be watered immediately after potting.

There are several relatively quick and easy ways to propagate house-plants without growing them from seed. By these methods mature plants can be the source of smaller, young plants in a short time. The most common methods are by using leaf and stem cuttings, by dividing the roots, and by air layering.

The leaves and stems of many common houseplants will develop roots and new shoots if placed in water or a rooting medium (such as perlite, vermiculite, or sand that is kept moist). The leaf cutting method works with plants such as African violets, gloxinias, echeverias, and sedums, which have fleshy or succulent leaves. Stem cutting can be used with most plants having upright or creeping stems. Propagating plants by dividing their roots is effective with plants that grow in clumps or form more than one crown of leaves; for example, African violets, begonias, the Chinese evergreen, and echeverias. They can be pulled apart so that a few roots will adhere to each section.

The air layering method is usually used for large plants such as the rubber plant, which often grows tall and whose stern grows only a tuft of leaves at the top. By this method a shorter plant can be made from the leafy top portion of the original plant.

First, a small notch is cut in the bare stem a short distance below the last leaf. Moist sphagnum moss is then wrapped around the cut and a piece of plastic is firmly tied around the moss to permit it to retain its moisture. After 7 to 10 weeks, a mass of roots can be seen growing in the moss. The stem should then be cut just below the plastic wrapping. The wrapping is then removed and the newly rooted upper portion of the plant is potted. In many instances the bare, potted stem that remains will grow a new leafy top if watered sufficiently.

Houseplants often thrive so well that their growth becomes overabundant and unattractive and should be controlled by pruning—cutting back the plant with a pair of sharp shears. Plants also need pruning when they lose their bushiness to tall spindly growth. A gentle form of pruning, called pinching, consists of removing the growing tips of the stems with the fingernails. Pinching can encourage lower, fuller growth; when used on flowering plants in their budding stage, it generally produces larger and longer-lasting flowers. (The reason is that the buds receive additional nourishment—that which would have gone into the growing stem tips.)

Houseplants are occasionally attacked by such pests as aphids, mealybugs, mites, red spiders, and scale insects. These pests thrive in the dry, warm air of heated rooms. Certain species can be discouraged from attacking plants by frequently sponging the leaves or spraying the plants with lukewarm water. Aerosol insecticides or miticides can be used on plants already infested. Most insects lay their eggs under the leaves, so the undersides of leaves as well as the tops should be sprayed.