MOST OF THE rhododendrons we grow in our gardens are hybrids - distinct plants created by mixing up genetic material from two different kinds of rhodies. Breeders are after bigger flowers, disease-resistance, flashier colors.

In contrast, species rhododendrons are genetically unaltered by the human hand. They remain as they were when first collected in the wild. What difference does this make when selecting rhododendrons for your garden?

"Many people grow species rhododendrons for what they represent, their wildness," says Steve Hootman, curator of the Rhododendron Species Foundation Botanical Garden in Federal Way. When you grow a species rhododendron you are nurturing an identical plant to one first sighted in the misty mountains of Japan or painstakingly collected from the steep slopes of the Himalayas by a dauntless plant explorer.

Besides the romance, the bit of history they bring to the garden, what are the practical reasons to seek out species plants?

Hootman says gardeners choose species rhodies for their character. Attractive foliage and bark, rather than bloom, is often the prime reason. Instead of a large blob of green, which flowers for three weeks of the year, distinctive foliage and bark provide interest in all seasons. The flowers have all the characteristic beauty one expects of rhodies, plus they are purer in color, and often fragrant.

And any gardener with limited room (and don't we all end up,

later or usually sooner, desperate for more garden space?) will appreciate that species rhodies are more compact than the often ungainly hybrids. You know those leggy rhodies that started out as foundation plantings and now screen the windows? Not a problem with the tidier species; kind of like replacing a Great Dane with a trim little terrier.

A mission of the foundation is not only to find and introduce worthwhile species rhodies into the horticultural trade, but also to preserve these treasures for the future. "If people think we're cutting down forests quickly here, they should see the destruction in Asia," says Hootman, who travels to Asia a couple of times a year. He plans a collecting expedition to Tibet in June; one of the goals is to search out the best species rhodies for modern gardens.

The foundation's 24-acre botanical garden will open a newly renovated woodland garden in late April highlighting a group of species rhodies called Taliensias. The long-lived, slow-growing mountain species from China is particularly successful in our climate. At the garden, an acre-and-a-half of beds and paths beneath large trees has been redesigned and the soil enriched. Here primroses, magnolias, corylopsis, hellebores and meconopsis join 45 different species of Taliensias in a spring garden which will be at its peak of bloom when it opens to the public in late April.

Lest species rhodies sound too tantalizing to do without, a great variety will be available at the foundation's spring sale. The biggest of the early spring sales, it will be held at the botanical garden from 3 to 6 p.m. April 3, and 9 a.m. to 3 p.m. April 4. Little terrestrial orchids, alpines, choice perennials, trees, shrubs and herbs will join the species rhodies on the sale tables. The Rhododendron Species Foundation Botanical Garden is at 33663 Weyerhaeuser Way S. in Federal Way (at Weyerhaeuser Corporate Headquarters). Call 253-661-9377 for information and directions.

Valerie Easton is a horticultural librarian and writes about plants and gardens for Pacific Northwest magazine. Her e-mail address is vjeaston@aol.com

Now In Bloom: What garden can do without the speckled leaves and tiny, bright flowers of old-fashioned, sturdy Pulmonaria, or Lungwort? They bloom early and continue flowering for months, most curiously in flowers of pink and blue on the same plant. Cut back after blooming for a new flush of leaves that will serve as robust groundcover all summer.