Bettie Willard wants to make sure you enjoy her magnificent 414-square-mile "back yard" especially the starkly beautiful sections above timberline.

So the veteran Boulder, Colo., botanist, ecologist and world-recognized alpine tundra expert has published "A Roadside Guide to Rocky Mountain National Park" with Susan Quimby Foster (Johnson, 309 pages, $12.95), a book to slip into your car the next time you head toward the park's high country.Willard's middle name should be "Wow," because she uses that exclamation frequently as she talks about the wonders of nature, especially the exquisite tundra plants, which are fragile but marvelously resilient once they get a foothold in an undisturbed environment.

She dates her lifelong interest in botany to childhood - she grew up near Palm Springs, Calif., the only daughter of a teacher mother and photographer/landscape painter father.

"I was toddling after my father out in the fields from the time I could walk," she said. "My first friends were the flowers and animals and other things. By the time I was 16, I was leading nature walks and lecturing about the plants."

After receiving her undergraduate degree from Stanford in 1947, she completed a course at the Yosemite Field School of Natural History and earned teaching credentials at the University of California at Berkeley. She did teach, but briefly: "I like the out-of-doors too much," she said.

It was the decision to study for her doctorate at the University of Colorado at Boulder that set her life's course.

"I got hooked on the Rocky Mountain National Park," she says, "the tundra plants are so lovely, so rare, so delicate looking." She hiked and studied and, in 1954, received a Ford Fellowship: "That gave me the chance to spend 14 months in Europe studying tundra in the Alps."

Willard's career boasts many peaks, including founding the environmental sciences program at Colorado School of Mines in Golden, originating the annual seminars at the Aspen Center for Environmental Studies, serving as trustee at the Thorne Ecological Institute in Boulder and the Colorado chapter of the Nature Conservancy, and founding the nature seminars at the Rocky Mountain National Park. She won national recognition in 1972 when President Nixon appointed her to the Council on Environmental Quality in Washington, D.C. And not least, she has written six books, including the popular "Land Above the Trees" with A.N. Zwinger.

Since 1958, she has kept a scholar's eye on tundra plants near Trail Ridge Road in the park, which is located about an hour's drive northwest of Denver. She is relatively happy with the survival rate of tundra today.

"It's improving. When I came to Colorado 33 years ago people just tramped wherever they wanted, with no regard to the tundra. It can take eight years for a cushion plant to recover after a foot crushes it. We have to realize that the tundra is fragile, there's no doubt about that, but we do want people to see it and enjoy it."

Willard is not advocating a "people-stay-out" policy. "The best protection for any wild land is a road or a trail going where people want to go," she said.

As Rocky Mountain National Park celebrates its 75th anniversary, park visitors interested in learning more about the landscape can tuck a copy of Willard's guidebook in their pockets. It measures 6 by 9 inches (convenient for stuffing into backpacks and gloveboxes) and is available in area bookshops as well as the park tourist information center.

It is well illustrated with photos, maps and activity symbols, and offers seven individual guides, each of which can consume from three to five hours. The Trail Ridge and West Slope trips each require a full day's journey.

This is a textbook on geology, biology, glaciology, ecology, anthropology, archaeology, history and hydrology.

But most of all, the park is full of adventure: 113 peaks over 10,000 feet; Trail Ridge Road, which is the highest continuous paved road in the country and 355 miles of hiking trails. And don't forget the tundra. Pack along a magnifying glass and study an alpine plant closely. Willard promises you will be delighted with its delicacy and perfection.