A very nice variegated ivy has been relegated to the rear of my fluorescent light garden. Last year it was beautiful and many people asked for a cutting from it. This year it is a straggling, unkempt sprawl, and I have to confess neglect (it happens in the best regulated gardens). The plant was not pinched and pruned when it should have been.

Pinching and pruning are operations performed on a plant to maintain or improve its size, shape and health, or to train it.

After the dark days of November through January, some of your plants, such as coleus, begonias and impatiens, may be looking emaciated - thin and pale and leggy - a condition which in relation to plants is called "etiolated."

Plants grown in poor light show this effect, and faulty watering and fertilizing practices contribute to it. Judicious pinching or pruning will achieve wonders in restoring the appearance and vigor of such plants - along with better light, of course.

Another candidate for pinching or pruning is the plant that has grown so vigorously that it is a tangled mass of greenery or occupies more than its allotted space.

Pinching is a simple form of pruning. It is done by removing the new growth at the tip of a branch; use your thumb, or thumbball, and forefinger to pinch out the tender young shoot. Pinching encourages buds to develop farther back on the stem; more branches are the result, and extra growing points for flowers on flowering plants. When those new branches have developed they too may be pinched at the growing tip. The plant becomes bushier and more floriferous.

Begonias, Swedish ivy, coleus, geraniums and impatiens benefit from pinching (or from pruning). When the avocado grown from a pit is about 10 or 12 inches tall, pinch out the growing tip to cause it to branch; otherwise, it will grown to a tall, gangling specimen. Philodendron can be pinched so that it won't spread too far. Pinching is especially effective on trailing plants such as ivies, gynura (velvet plant) and wandering jew.

The purpose of pinching is to force branching, so it won't work on nonbranching plants. Some plants that should not be pinched or pruned are bromeliads, chlorophytum, African violets and orchids. Cacti and some other succulents are not pruned. Nor are ferns. Palms will die if the terminal bud is removed. The pruning of palms deals mostly with mostly with removal of old unsightly leaves.

Pruning is a more radical treatment to improve the growth and shape of a plant by selective removal of stems and branches, as well as any dead, diseased or misshapen parts.

Pruning is done with a sharp instrument, such as a razor blade, scissors, or small pruning shears.

Prune a branch just above a node - that is the point from which a branch or leaf grows. At that point buds are located from which new growth will develop. Generally, it is safe to remove as much as one-third of the plant's foliage at one time, but approach the job slowly and selectively. Remove branches to shape the plant, to allow remaining branches to have better light exposure and air circulation, and to control rampant growth.

Writing of potted trees in the Brooklyn Botanic Garden Handbook on Houseplants, Ernesta D. Ballard, president of the Pennsylvania Horticultural Society, says: "As an indoor tree grown from year to year, new growth will appear at the tips of the stems and branches, and older leaves will yellow and eventually drop off. How long this takes depends largely on the species. At some point, pruning will be necessary to keep the tree to a reasonable size and to encourage new branches along the stems to replace fallen leaves. At the axil of every leaf is a bud capable of developing into a branch. On most trees these embryo branches can be induced to develop by pruning the tips of existing branches and the main stem. In the case of flowering and fruiting trees, pruning also produces more andbetter blooms and fruit."

Cutting back is a drastic type of pruning. A schefflera that has become too tall, with leaves only at the top can be cut back to 10 or 12 inches from the top of the pot to force new growth. A rubber plant, grown tall and top-heavy, can be cut back also. The potted stumps are unsightly but they must be cared for to continue in growth. Give them good light, a humid environment, and, because they are leafless, reduce the amoount of water given until bud and leaf growth resumes.

Grooming a plant is a form of pruning. Cut off dead flowers and disfigured leaves; trim brown edges to the natural contour of a leaf, as for examaple on chlorophytum and streptocarpus. The plant will be reinvigorated, and its appearance improved, by such incidental attention.

The roots of plants can be pruned as an alternative to top pruning. Root pruning will help to reduce rampant growth and is a means of controlling the size of plants. It is as important as top pruning in the care of potted trees. It is the only means of control for those non-branching plants mentioned above which cannot be top pruned.

When you undertake root pruning, carefully remove the plant from its pot. Gently untangle and trim away some of the longer dark-colored roots. Use a sharp knife or shears. Revolve the plant and trim from all sides of the root ball without damaging the central ball. A good measure is to reduce the size of the root ball to the point where there is one inch between the roots and the container from which the plant was removed. Repot in a clean pot of the same size, using fresh soil.

For plants which can be top pruned it is desireable to give a light top pruning at the time of root pruning so as to reduce the leaf expanse and the loss of moisture while the plant recovers from the root pruning.

When you have finished a top pruning job your plant may appear shorn - as someone with a too-short haircut. But do not despair. With good culture, the plant will send forth new leaves and branches and the appearance and health of the plant will improve. A leggy, spindly plant cannot do the job for itself so it will never look any better unless you are willing to "give it a hand."