Maybe you have been wondering if you should repot your house plants this spring. Start with a question. Does the plant really need it? There are ways to tell:

Roots have filled the pot. Roots show on the soil surface, or grow through the drainage hole. New leaves are smaller than average for the plant.

Another circumstance, sometimes overlooked, in which repotting may be needed, is when the condition of the soil is no longer congenial for root growth. This occurs when growing mixes have been used that contain a large amount of organic matter, such as those for streptocarpus, African violets, begonias and ferns. Under the influence of warmth and frequent watering the organic matter breaks down and the soil becomes compacted so that roots do not get enough air.

To help you decide about repotting, examine the condition of the roots by removing the plant from its pot. If there is a solid rootball surrounded by a fine mesh or network or roots, repotting is in order. Some plants make arrive at this condition and need repotting only every other year. Some, such as Ficus, Schefflera, Boston fern, palms and cacti, can remain undisturbed for several years if they are well taken care of.

If a plant has already grown as large as you want it to be, you need not repot it. Just remove some of the soil at the top of the pot and replace it with fresh mix. Or transfer the mature plant to a clean pot of the same size; prune the roots and top a little and remove some of the old soil and replace it with fresh.

Some foliage plants, for example Ficus species, do very well when their roots are crowded. Many flowering plants bloom better when slightly pot-bound.

When repotting, use the next larger size pot, that is, move from a three-inch to a four-inch pot, or from four to six inch, and so on. Roots need to be fairly snug in the pot. A pot that is too large may not only be out of proportion to the size of the plant but it will hold too much soil, which tends to retain more water than the plant can use, and roots will rot.

Always use pots that are absolutely clean, either new pots or well-scrubbed old ones. Clay pots-new or old-should be soaked overnight in water so that when used tha porous clay will not draw moisture from the potting mix.

For potting soil, it is simplest to rely on ready-made potting mixes sold in packages at garden centers, variety stores and by mail order, especially if you have only a few plants.A recent column in this space covered choices between ready-made and homemade potting mixes.

When all is in readiness, remove the plant from its pot. Do not tug on the plant.Put your hand over the soil surface with stem or base of the plant between two fingers; invert the pot and lift it off. If it does not come off easily, jar it against a counter or table to loosen the plant. With some plants it may be necessary to break the pot; for instance, The roots of a large asparagus fern will adhere to the inside of a clay pot. Better to break the pot than damage a plant.

With thumb and fingers, crumble away some of the soil ball. If roots form a solid ball, gently loosen them with a pointed stick.

Places pieces of broken pot or small gravel over the drainage hole of the new pot. A thin layer of sphagnum moss will help prevent the mix from washing out through the drainage material. Then start to fill the pot.

The potting mix will be more manageable and less "dusty" if it is slightly moistened with warm water before using it. pour in a layer of mix deep enough so that when you set the roots of the plant on it, the plant will be at the same depth, in the new pot as it was in the former pot.

Next, start filling in around the root-ball, tamping with a potting trowel or plant stake. Gentle finger pressure will help to assure good contact of roots with the new soil mix.

Keep adding mix until all exposed roots are covered. The new soil level should be about an inch below the rim of the pot (half and inch on very small pots) to allow space for watering without overflow.

Use tepid water to water the plant. Note: Cactus plants are potted into almost-dry soil and are not watered for at least a week after reporting.

A newly potted plant should have less than normal light for a day or two. If it shows signs of wilting, cover it with a plastic bag perforated for ventilation. Do not fertilize a newly repotted plant for about a month or until new growth is evident. Be espescially careful about frequency and amount of water. Wait until the soil has dried a bit, then resume watering.

For most house plants, early spring is the best time to do any necessary repotting.