Up a long and winding road, amid the shade of tulip poplars and the scent of earth, the tiny trillium awaits its admirers. For more than half a century, Trillium viride and other woodland flora were the joy of Pamela Cunningham Copeland, a passionate gardener who shared her majestic, 230-acre estate with others only a few times a year – all the while preparing to open its ornate iron gates to the public in perpetuity.

Mount Cuba, once one of Delaware's greatest private pleasures, is now a treasure for all. At the behest of Mrs. Copeland, who died at 94 in 2001, the Mount Cuba Center for the Study of Piedmont Flora will operate as a not-for-profit horticultural institution, where nature lovers may tour by appointment. It brings to five the number of elaborate gardens planted and bequeathed by DuPonts in a 10-mile circle.

On a dew-dripping morning, Rick Lewandowski, the center director, tramps past a pair of yews, evergreen sentries to a private formal garden. An allee of gum trees forms an inviting path. "When the trees drop their leaves, you can see the Delaware Memorial Bridge," he says. "It's simply an incredible piece of land."

Situated in the rolling hills of Greenville, Mount Cuba is one of the highest points in Delaware, home to such celestial wildflowers as monk's hood and jack-in-the-pulpit. But in 1935, when Lammot du Pont Copeland built a Georgian-style home there because Pamela enjoyed the view, the stately brick manse stood in the middle of an idle hilltop cornfield. Battered stalks lined the grand walkway to the house then, but out of the fallow farm would spring a new and wondrous crop of rhododendrons, azaleas and hollies, the verdant princes of the piedmont. Among the first plantings were the yews, a gift from industrialist Pierre S. du Pont, Copeland's uncle and the founder of Longwood Gardens in nearby Pennsylvania.

Mrs. Copeland grew with her surroundings, maturing as a gardener throughout her long and fruitful life. Her extraordinary personal evolution would become inextricably intertwined with the gardens. For example, she mandated that lilacs be pruned to grow no taller than eight feet, discerning it was the ideal height for someone strolling past the hedge to enjoy the luxuriant scent. Her sophisticated eye took in not only showy blossoms, but each part of a plant. "If the foliage on the roses was nice, she noticed," recalls gardener Vic Piatt.

The white roses called Pascali still bloom in the cutting garden at Mount Cuba. Delphiniums, coaxed into flower by Mother's Day, begin life in a cold frame, an incubator of sorts for flora. But the philosophy at Mount Cuba is to choose plants for their origin rather than their beauty. They must be native to the piedmont, the lovely crescent of land which stretches from New York to Alabama, bordered by the peaks of the Appalachian and Blue Ridge mountains on one side and the flat, sandy Coastal Plain on the other.

Currently, plants which don't grow naturally in the piedmont are being weeded out. Mrs. Copeland's tropical orchids, for example, were dispersed to hot houses throughout the east, ranging from Longwood Gardens to Smith College in Massachusetts. A garden of Asian species will be supplanted by native flora in the near future.

In this interpretation of the piedmont, towering tulip poplars form the canopy for shrubs and flowers below. They grew straight and tall under Mrs. Copeland's instructions to assiduously lop off the lower branches to force the trees upward. "She managed them brutally, but you can see how effective it was," Lewandowski says.

More subtly impressive is the trillium, a relative of the lily which bears a whorl of three leaves and a single, delicate flower. Despite their effortless beauty, persuading trilliums to propagate is a difficult task, requiring years of work by horticulturalist Jeanne Frett. It is an achievement quietly trumpeted by the Mount Cuba staff. "We have the finest display of trillium anywhere in the United States," Lewandowski says.

In all, there are more than 2,000 species of plants at Mount Cuba, from the candelabra primrose (Primula japonica) to snakeroot (Cimicfuga racemosa). A half-dozen cultivars developed at the estate are now sold at commercial nurseries; among them are: Aster novae-angliae, commonly known as purple dome; Cornus sericea or silver and gold; Heuchera americana or garnet; and Solidago sphacelata, called golden fleece.

Mrs. Copeland put down roots in gardening early, accompanying her mother as she made the rounds through the gardens surrounding her girlhood home in Connecticut. Her mother gave her treats for memorizing the Latin names of wildflowers the two spied in nearby woodlands. Although Mrs. Copeland's first adult forays into the garden were restricted to growing lettuce and cutting flowers, her youthful delight in the natural world would be revived later in life.

"In the autumn, she liked to have the leaves on the path, so she could shuffle through them like she did when she was a child," remembers Ed Allen, who gardened for Mrs. Copeland for 25 years. To that end, landscapers would quickly sweep leaves onto the walkway as the lady of the estate approached, heralded by her characteristic rapid stride, punctuated by the tap of her cane. When the rustling of the leaves stopped, Allen knew her stroll was complete. "And we swept the leaves away again."

The man in charge of her mother's garden was a Scot, who worked in a suit and tie, bowler hat and green canvas apron. When Mrs. Copeland decided to immerse herself in the piedmont in 1983, she turned to Richard W. Lighty, who coordinated Longwood's graduate program at the University of Delaware. Lighty directed the Mount Cuba center for 15 years before retiring to his own seven-acre garden in Kennett Square, Pa. Lewandowski, formerly director of horticulture at Morris Arboretum in Philadelphia, was named director in 1998.

This will be the second time Lewandowski has been at the helm in a time of transition. He supervised the transformation of the arboretum from a quiet estate into a world-class botanical garden and rebuilt its plant collection during his 16-year tenure there.

A few years after Mrs. Copeland was transplanted from New England to northern Delaware, she turned to Thomas Sears to design a formal garden. After World War II, she asked renowned landscape designer Marian Coffin, who had planned spaces for Henry Francis du Pont at Winterthur, to complete the plan. Coffin suggested rectangular hedges of azalea, circles of flowing, unclipped boxwood and flowers in vivid hues, all centered around a pool.

The design created a transition from the Copelands' formal home, furnished in mostly Chippendale antiques and paneled in wood salvaged from southern manors, to stands of trees beyond. But the overall plan for Mount Cuba took a new course when two tracts of land were added to the estate, one a meadow, the other woodlands. "Marian Coffin was interested in color and shape," Lewandowski notes. "But for the rest of her life, Mrs. Copeland would be interested in plants." To that end, she would swoop in to transplant wildflowers from farms slated for development. Soon, lady's slippers gained a foothold in the garden. A series of man-made ponds became the new home of such moisture-loving plants as vanilla-scented lady's tresses, white orchids and marsh marigolds. Even in winter the woodlands are vibrant with the scarlet blooms on Witch Hazel trees.

As Mount Cuba's transition to a public place progresses, the Copelands' former home will become a center for lectures and workshops. The team of 25 gardeners and landscapers will continue to define and refine the gardens. And Mrs. Copeland's beloved tulip poplars will grow taller. "All the wonderful things here will be preserved, just as she wished," Lewandowski says, "except more people will get to see it."