GARDENING : HIGH-OCTANE CONTRAST IN GAS STATION GARDENS.

Byline: Joshua Siskin

Someday, when historians look back at the waning years of the 20th century, the gas station garden may well be regarded as the quintessential artifact of our times. Gas station gardens, consisting of planters filled with annuals and an occasional palm, are a vain attempt to bring opposites - polluting hydrocarbons and pulchritudinous pansies - together.

Our era will be remembered as a period when people wanted to have it all - from the visible signs of prosperity to a social conscience, from a fancy, air-polluting vehicle parked in front of the house to a healthy, organically nurtured vegetable plot in back.

The gas station garden may be viewed as a study in contradiction, but also as an attempt to assuage guilt or build public image. No enterprise has polluted the Earth more than the drilling, refining and burning of fossil fuels, to say nothing of their accidental dumping in the world's oceans. As if to atone for this environmental havoc (or to divert our attention from it), the purveyors of gasoline have, in recent years, adorned their filling stations with flower beds.

Not that there's anything wrong, in the end, with gas station gardens. The more flowers that surround us, the better. Why should flowers only be for life cycle ceremonies like birthdays, marriages and death? In some European countries, fresh flowers are brought home as often as fresh milk or eggs. In our upside-down world, it is entirely possible that gas station gardens may ironically serve to increase our appreciation of flowers.

On the southeast corner of Van Nuys and Ventura boulevards, in Sherman Oaks, there is a Union 76 station with planter beds of simplicity and distinction. Pygmy date palms (Phoenix roebelenii) are under-planted with crimson-leafed celosia (Celosia Huttoni). Celosias are annual flowers known commonly as cockscombs. There are plumed or feathered cockscombs, such as those at the 76 station, and crested coxcombs, whose flowers look like brains. Both kinds of coxcomb flowers are woolly to the touch and may be seen in pink, yellow, orange, gold and crimson.

The unusual flowers of the celosia create the mistaken impression that this is a delicate plant. Nothing could be further from the truth, as the celosia can go through the summer with a scant amount of water. As with all annuals planted in the Valley, though, it does best when protected from the full brunt of summer's sun. Amazingly vigorous and self-sowing in its tropical habitat, celosia is regarded there as a weed.

Celosias belong to the amaranth family. The word ``amaranth'' comes from the Greek for ``unwithering'' and, yes, the flowers of the plants in this family are popular in dried arrangements. Love-lies-bleeding (Amaranthus caudatus) has drooping red tassel flowers and young leaves that may be eaten when cooked. I once had a student from Southeast Asia who uprooted pigweed (Amaranthus hybridus), a common volunteer in Los Angeles gardens, for the purpose of consuming its leafy parts and its grainy seeds.

Mrs. M. Korman of Encino writes with the following question: ``Could you recommend nectar plants that attract butterflies?

The latest edition of the `Sunset Western Garden Book' contains four pages (pages 82-85) with lists of plants for a butterfly garden. Adult butterflies, in common with beneficial insects (parasitic wasps, lacewings, and ladybugs), require nectar-producing plants to be drawn to your garden. These include yarrow, agapanthus, snapdragon, penstemon, lobelia, and sweet alyssum, apple and citrus trees, lantana, lavender, honeysuckle and, of course, the butterfly bush (Buddleia). Plants that provide food for caterpillars complete the setting for a butterfly garden. These food plants include: hibiscus, rose, passion vine, oak, sycamore and nasturtium.

Barbara Otto of Burbank writes: ``I have a 250-year-old California oak tree in my back yard. I was told it's not good to plant under oaks, so I surrounded the trunk with river rock. However, I want green vegetation and color near the tree. Will impatiens, ajuga and hosta grow in the shade inside or outside the drip line (canopy perimeter of the tree?''

Great care should be taken that established oak trees get no more water than they have been accustomed to throughout their lives. Overwatering such a tree will result in root rot. An old tree such as yours, I would assume, has not been watered much, except for winter rain. Outside the drip line, you should plant California natives that do well in dry shade, as opposed to the thirstier plants you mention. I would recommend meadow rue, with leaves that resemble maidenhair fern; heuchera or coral bells, with white, pink or red flowers; Catalina perfume (Ribes viburnifolium) with leaves that become fragrant after a rain. These and other shade-loving natives are available at the Theodore Payne Foundation nursery in Sun Valley.

Tip of the week: Now is the time to prune overgrown shrubs. Instead of turning everything into meatballs or gumdrops, consider lacing out your plants. Cut out all branches and shoots that bend below the horizontal. Allow vertically growing or gently arching shoots to remain. Do not top or head back the plant. The result will be a thinned-out shrub whose natural shape has been preserved.