IN THE GARDEN BRINGING HIDDEN SURPRISES TO LIGHT.

Byline: JOSHUA SISKIN

Those of us who write about plants are among the most privileged of people. Our easy access to the world of plants puts us in constant touch with botanical treasures that remain hidden from most people. Luckily, there is a garden with exactly these kinds of treasures on display, open to the public at no charge, smack dab in the middle of the San Fernando Valley.

I am talking about the botanic garden at California State University, Northridge. If you never visit CSUN's garden, your perspective on what you can grow in our area will be forever diminished, limited to what is sold in nurseries. After your visit, you will realize the vast and rich spectrum of plants that can be grown, without much fuss, in Valley gardens. After seeing the many exotic plants on display, you may well imagine that this is only a hint of all that we could grow; your eyes will be opened to the vastness of the plant world and the myriad possibilities it offers us for our gardening pleasure.

At the CSUN garden, the plant I found most intriguing was the twisted myrtle (Myrtus communis ``Boetica''). This plant is ideal for an informal, drought-tolerant hedge. It has deep green, diamond-shaped leaves in dense whorls up and down the stem and, once established, needs water only once a month. It would also serve admirably as a garden accent or small specimen tree, reaching a mature height of 9 to 12 feet. In Phoenix, which is both hotter and drier than the Valley, the twisted myrtle is a popular plant for both container growing and bonsai treatment.

Perhaps the most astonishing and satisfying group of plants at the Northridge botanic garden is the Hebe (HEE-bee) collection. Hebes are considered problematic because of their sensitivity to fungal diseases that, without warning, scorch their shoots and lead to an early death. To keep ahead of this contingency, the keepers of the Northridge botanic garden make cuttings of their Hebe specimens, which are rooted and ready for planting if and when the mother plants die. Hebes have delicate, sequined, bottlebrush type blooms in every shade of blue and violet. Their shiny foliage varies from simple green to cream and white, to gray to purple-tinged.

Under a Valley oak (Quercus lobata), three natives have been planted to demonstrate what can be safely grown under this magnificent local tree. Ribes viburnifolium (Catalina perfume) has foliage that expresses its sweet scent following a rain. Heuchera, otherwise known as coral bells, is a ground cover with sprays of salmon, coral, red or white flowers and clumping maple-shaped leaves. Thalictrum polycarpum or meadow rue is a soft ground cover with tall outcroppings of ferny shoots.

Speaking of ferns, the CSUN botanic garden has an amazing Australian tree fern variety called ``Brentwood'' that is faster-growing, more robust and larger than the type typically planted in our gardens. There is also an unusual, fringed holly fern that is virtually maintenance free. In addition, Brenda Kanno, associate curator of the garden, has collected an impressive group of greenhouse ferns.

Brian Houck, supervising horticulturist of the CSUN botanic garden, is intent on publicizing the Valley's best-kept horticultural secret. The third annual CSUN twilight garden party will be held from 5 p.m. to dusk Aug. 23. Tours of the many exotic plant displays will be conducted against a backdrop of live music, art exhibits, and a spread of hors d'oeuvres and wine.

Houck also extends an open invitation to anyone who would like to volunteer to work at the garden. Volunteers meet there every Thursday morning to assist in maintenance and propagation. Nedra Bushby, a member of the highly dedicated troop of volunteers, has donated nearly 200 different cymbidium orchids, among them some rare trailing varieties, all of which are on display in a shade house.

The garden, located just north of Nordhoff Street on Zelzah Avenue, is open 8 a.m. to 5 p.m. Monday through Friday. For more information on the garden, call [phone].

TIP OF THE WEEK: One of the easiest and most rewarding California natives to grow in the Valley, on display at the CSUN botanic garden, is the island bush snapdragon (Galvezia speciosa). It is a large shrub that produces brilliant red flowers on and off throughout the year, requiring little if any water once established in the garden.