VALLEY GARDEN LIKE EDEN'S.

Byline: JOSHUA SISKIN

``You are nearer to God's heart in a garden than anywhere else on earth.''

These words are painted on a sign in the garden of Marie Odenheimer Thomas. In truth, she has transformed a backyard hillside in Sherman Oaks into a virtual Garden of Eden.

Thomas' garden is virtually free of weeds and pests, a testimony both to her soil, to the breeze that blows through her garden every afternoon and to the occasional pest control measures she employs.

You can tell that Thomas has good soil by the abundance of plants that self-sow and the variety of ordinarily finicky perennials that naturalize or come back every year in her garden. Her nasturtiums in every shade of orange and gold, her lilac larkspurs, sky blue forget-me-nots, fragrant sweet peas, florist chrysanthemums, dark and light blue lobelia, and normally temperamental cineraria are all growing from seeds that germinate where they have fallen or have been moved by water, wind, or avian creature. Her plants grow in such density that weeds can hardly find their way in.

Dahlias are found everywhere in Thomas' garden, thick clumps of dahlias which are obviously enlarging their girth from one year to the next. Just as remarkable are her lilies - and I am talking about true lilies, such as Easter lilies, that grow from bulbs - which have come back annually for more than a decade. Her true blue delphiniums also persist for years, a phenomenon that depends on well prepared-soil and application of snail bait the moment succulent new basal shoots appear. Finally, there is her peony, a glorious, vigorous plant that has been in the ground three years and shows off extraordinary pink flowers each spring.

Did I say Valley garden? Although her garden is technically in Sherman Oaks, it is topographically more hillside than Valley, situated halfway up that long incline between Ventura Boulevard and Mulholland Drive, between Sepulveda Boulevard to the west and the San Diego Freeway to the east. There is a salubrious breeze that blows through her garden every afternoon, drying up any potentially harmful excess water - an invitation to pests of all kinds.

The most memorable specimens in Thomas' garden are her several hundred roses. Before planting a rose, she digs a hole that is two feet deep and two feet wide. Liberal quantities of products such as Supersoil and Gromulch are put back into the planting hole together with some native soil. Superphosphate is added to make sure roots get off to a fast start. This preplant ritual results in amazing first-year growth, which may exceed 6 feet where her climbing roses are concerned.

Along her backyard slope, Marie's husband Robert has built a hooped arbor out of schedule 40 PVC pipe. Thomas has planted several hybrid musk roses in her garden. Her favorite is ``Sally Bowles,'' which produces huge 50-bloom clusters on terminal shoots. The flowers open up ivory, blushed with pink and gold, and then fade to white. Although not a true climber, ``Sally Bowles'' is vigorous enough to ramble up her arching arbor and beyond. The pink ``Kathleen''' and the coral ``Cornelia'' are other hybrid musks in Thomas' collection. These roses are nearly ever-blooming, lightly fragrant and capable of growing in partial sun locations.

Thomas also has many true climbers, including these nonstop bloomers: ``Altissimo,'' which has velvety red single flowers, ``Eden,'' a large, strongly fragrant, tightly layered pink rose, and ``Fourth of July,'' a red and white.

Thomas has a fondness for miniature roses and recommends ``Starina,'' an electric red, ``Popcorn,'' whose white flowers tinged with yellow are always in bloom, and ``Rainbow's End,'' which really looks like several different roses in one since one shoot on a plant may be showing yellow roses, another shoot orange, another shoot pink, and still another shoot red roses, all at the same time.