IN THE GARDEN IT'S A GREAT TIME TO BEGIN PLANTING.

Byline: JOSHUA SISKIN

If you have delayed planting because of the hot weather, delay no more.

October is the best time of the year to plant a Valley garden. Daylight hours are increasingly scarce so that even a hot day will lose steam before it can cook or bake a new planting.

In our climate, roots grow fastest and deepest in October. If you are planning a backyard graduation party for next June, and you want to spruce up the landscape in the meantime, do so now. Shrubs, vines and flowering perennials of all kinds will look better next June if they are planted now than if you were to wait and plant next spring.

During the fall, a plant devotes nearly all of its resources to root growth, so you may see little, if any development of new stems and leaves at this time. But have no doubt. Fall's invisible underground growth will bear heavy dividends in flower and foliage starting around the middle of February, which is when our precocious spring season usually begins.

Plant selection, of course, is a highly personal matter, but you might wish to consider the following few species if you are thinking of starting or adding to a garden this fall. These plants would probably be more visible if their growth habits were more precisely understood.

SHRUBS: The princess flower (Tibouchina urvilleana) is one of the most glorious if least understood shrubs. It needs half a day of sun, regular water and a healthy dose of fertilizer after each flowering flourish is over. It should be pruned down to a height of 3 to 4 feet in early spring. If you treat this shrub right, it will reward you with large, silky, purple blooms most of the year. 'Torch Glow' bougainvillea has tentacled branches with dark, rose-colored bracts adhering to the stems. This bougainvillea is more of a static living sculpture than a rampant plant and peaks out at a manageable height of around 6 feet. Its pruning requirements are minimal.

VINES: Clematis is entirely undeserving of neglect and yet, somehow, it is almost forgotten as garden fare. As long as its roots are cool, clematis will spiral without complaint up patio posts, climbing roses, prickly conifers and every kind of tree trunk. Clematis needs little rooting area to thrive, existing happily in a terra cotta pot or narrow planter. Both deciduous and evergreen types grow nicely in the Valley. Flowers are up to several inches in size and appear in pink, blue, purple and white.

Costa Rican nightshade (Solanum wendlandii) is somewhat cold-sensitive but worth the risk. Although deciduous, it puts out a profusion of 2-inch lilac blue flowers throughout summer and fall.

HEDGES: Once it reaches a height of 5 feet, blue potato bush (Solanum rantonettii) flowers virtually year-round in full or partial sun. Unfortunately, many people insist on keeping it small, as a lollipop or topiary subject, and it soon loses its luster in this form. Left to grow without constraint, it will reach 10 feet or higher soon enough and may be used to hide a chain-link fence or block wall, or simply as a privacy screen.

PERENNIALS: Japanese anemones are a fall surprise that no garden should be without, announcing their arrival with large sprays of white or pink flowers. However, if their roots are disturbed - a likely occurrence during much of the year when they are nothing but a subterranean clump of roots - they flounder.

Hellebores are the understated beauties of the winter garden and are worthy of the plentiful organic amendments that they demand.