Sprightly geranium thrives on no-fuss gardening

Perky pelargonium will bloom all summer long, even if you skip the fertilizer , forget about watering for a week, and refer to it as a ''geranium'' - its common title.

Most of us tend to take this sun-loving plant of South African ancestry for granted, relegating it to a minor niche in the yard. Yet there are more than 4, 000 varieties and species, with leaf and flower forms so diverse and beautiful that there is an International Geranium Society (6501 Yosemite Drive, Buena Park , Calif. 90620), plus national shows every year.

Available in solid and multicolors, either brilliant hues or subdued; in dwarf, standard, and climbing varieties; with scented leaf, or flowers aromatic enough to be used in potpourris, there's a pelargonium, or geranium, to suit every gardener. Nor do you have to pay fancy prices for even the fanciest of specimens. Cuttings are the primary means of propagation, and you can get them from neighbors or make multiple copies from a single pot that you may buy yourself.

For best results, August and September are the recommended months for starting geranium cuttings destined for outdoor spring and summer bloom. For indoor winter gardens, you'll want to start thinking ahead the previous May and June.

Begin with healthy parent plants, selecting tips with firm, but not woody, growth. If you're not sure which is which, a good test for a sound plant is whether the stem snaps when bent but does not break completely through.

Discarding your ''tester,'' now go to work with a sharp knife, straight-cutting a 3-inch piece just below a stem node with two nodes above it. Snip off the lower leaves, but permit two upper leaves to remain. Remove all flower buds. The few leaves left manufacture food for the fledgling plant, but anything else encourages top growth before the cutting has a chance to develop an adequate root system.

Let the cut surfaces dry completely before placing them in a rooting medium.

It's possible to start your geranium ''babies'' in a glass of water placed in a well-lighted, but not too hot, window. You can also put them directly in the garden by wrapping the cut end with sphagnum moss or surrounding it with sand. Another easy method is to use sterilized commercial soil or washed sharp sand in a 3-inch pot, setting the cutting about 2 inches deep. Firm the soil or sand around the cutting so that it stands upright, taking care that the lower leaves do not touch the surface of the planting medium.

The ground should be well watered before insertion, and then kept moderately moist until the new root system forms. This takes an average of three weeks, although a few species can stretch the time to five months. Much depends on the time of year, stem condition, and placement of the plants.

Don't be discouraged if your young plants seem to wilt a bit the first day or so. This is normal, and they will soon absorb enough moisture to liven up.

Should your cutting be started in an extremely hot garden section, you may want to shade it a bit with newspaper or cloth until the new growth commences.

Once the growth starts, you just have to pinch out the centers occasionally to encourage a multiple branching pattern.

Fertilizer is not recommended, even for adult geraniums. Warm-weather watering varies, according to type, from once a week to every two weeks if outdoors, the key being when the soil dries to about one inch below the surface. Indoors you will need to water more often, using a ''dry to the touch'' soil guide.