IN THE GARDEN GRAVEL FILLS AN AESTHETIC NEED.

Byline: JOSHUA SISKIN

One of the hottest trends in landscaping involves use of gravel, decomposed granite and river rock, in all sizes and colors, for use as walkways, for mulch or for covering unsightly tree roots, for simulating rivers or stream beds, or simply for ornamentation.

The most attractive aspect to landscaping with rock or gravel is the maintenance. No watering or fertilization is required. Prior to placement of your rock or gravel, you need only lay down weed-control fabric, an inexpensive material available at most nurseries and garden centers. Without this fabric, weeds could be a problem.

Where walkways are concerned, you might want to consider pea gravel or the smallest-sized colored stones. Some people enjoy the crunching sound and soft feel of these tiny rocks under foot. Decomposed granite is, in my opinion, a highly underutilized alternative substance for footpath construction.

This buff-colored, coarse-grained material, known in the trade as ``DG,'' is not only far less costly than concrete, but also it allows tree roots to grow under it without danger of cracking. DG is also an economical landscape material that can always be replaced, later on, with richer hardscape alternatives, as budgets allow. When you order DG, spend a few extra dollars per yard to get ``stabilizer-added'' material. The stabilizer enhances compaction.

Large river rock is being used increasingly as mulch for drought-tolerant trees. Although the horticultural literature is full of plant species for use under California oaks and other native trees, it is always a tricky proposition giving enough water to keep the companion plants alive without giving too much water to the trees. You can find river rock in several sizes, ranging from 1 to 6 inches in diameter, with names such as ``Mexican beach,'' ``Arizona'' or ``Colorado cobble,'' in colors ranging from black and gray to beige, buff and red.

Utilizing a swath of gravel in a landscape to represent flowing water is common in Japanese gardens. Palm Springs Gold is a multicolored, 3/4- inch gravel that suits this purpose admirably. Of course, you can also use common gray gravel, as well as any of the stones or cobbles mentioned above, for your river or stream bed.

For areas of deep shade in side yards, low alcoves or corners of interior courtyards, or for hot sun areas where sprinklers have no access, colored stones are an aesthetically pleasing way of covering otherwise bare ground. Find a supplier of the many different kinds of stones available and choose the ones you like best. Jacoby, on Vanowen Boulevard near Canoga Avenue, is one such supplier. Check the yellow pages under ``Building Supplies'' for others.

TIP OF THE WEEK: If you can afford flagstone, considered the Rolls-Royce of pathway materials, you might want to plant in between the individual stone pieces, rather than cement the gaps. Drought tolerant herbs are often recommended for this purpose. Consider lemon or woolly thyme, chamomile, yellow ice plant, cushion bolax (Azorella), pink pussy toes (Antennaria), dymondia and baby tears for flagstone planting.