The only constant is the trim figure who traverses the gardens, weeding by starlight, gathering bouquets in the rain, occasionally plucking a lime for his gin and tonic.

Richard Lighty, Ph.D., is a celebrated teacher and horticulturalist, a breeder of plants and a designer of landscapes. But on the 7.5 acres in Kennett Square, Pa., he calls home, he is simply a man of the soil and all that comes from it. "In my heart, I'm a gardener," he says.

When he first surveyed the property in 1961, corn was the primary plant life there. Lighty yearned for tall trees, but found only nine, spindly ashes, "which I loathed."

He was a young man with a budding family, but happily his vision for the land stretched beyond his years. He took stock of the streams and swales and realized he could thicken the plot with fragrant viburnum and flowering cherries. Skunk cabbages would fare nicely in the marshy stretch. Astilbes, hostas and ferns would form a ground cover beneath the canopy of trees that would eventually grow. And the rancher already on the property would provide shelter, as well as a view of the gardens to come.

"The house mattered, but not that much," he recalls. "We are terrain people – good water, rolling hills, great topography. This property was a clean canvas, and a good one."

Coral bells and yellow false indigo in front of a Chinese snowball

On the day his family moved in, Lighty brought a truck bearing maples from nearby Longwood Gardens, where he was developing plants. He soon added a border of hemlocks around the perimeter of the property, a buffer against the development he knew was coming even then. He worked at Longwood by day and on his own garden after hours, frequently tending plots at night.

Soon, the one-time cornfield grew green with thousands of plants. The lace-cap hydrangea called Blue Billow blossomed in summer, when the freckle-barked camellia, Stewartia koreana, showed off saucer-size blooms. Witch hazel unfurled bewitching red shoots in the crystalline January air. Despite their exotic names and lovely bearing, most of the wonders in the garden were castoffs from Longwood or sprang from seeds, cuttings or divisions. "For the first 20 years, we spent maybe $45 for plants," he recalls.

The first plant geneticist at Longwood, Lighty also established and directed research and graduate programs at the University of Delaware. As a founding member and the first director of the Mount Cuba Center in Greenville, he became the architect of the late Pamela Copeland's vision of an expanse devoted to the flora of the piedmont, the fertile crescent that slices through southern Pennsylvania and northern Delaware on its verdant run from New England to the Carolinas.

Lighty calls Mount Cuba "my later-in-life inspiration, the epitome of native plant gardens." That spark took root at home, as well. At Springwood, one quarter of the land is devoted to native plants, such as trillium and wildflowers. Still, the larger landscape is astonishingly diverse, including such delights as pines brought home from an expedition to South Korea in 1966, a land that was to become a favorite source of unusual flora for Lighty.

"His garden is a reflection of his curiosity and interest in temperate plant species and his abiding love of gardening," says Jeanne Frett, assistant to the director at Mount Cuba. "One comes away from a garden visit with either a gift of keen insight or a particularly interesting plant – sometimes both!"

Now 69 and energetically retired, Lighty still takes joy in finding the right plant for the right spot. Blueberries and wintergreen thrive in acidic soil at the top of a hill. A less likely choice is the bamboo he grows, thinning the tranquil stand as he harvests stalks for plant stakes. "From the time I was a kid, I always wanted a bamboo grove," he says.

Lilium Tsingense, a tough, shade-loving lily with pagoda-like tiers of foliage

The boy who loved bamboo was born in the Midwest, where most folks are more concerned with growing grain. He realized he wanted to breed plants as he watched his father put in sweet Williams, noticing that some flowers were red in the center and white on the outside – and some flowers were the other way around. When he was in grammar school, Lighty's family moved to Huntington, West Va., where he met a lively girl named Sally, who is now his wife of 47 years.

At Springwood, the Lightys watched two children, a son and a daughter, grow taller among the poplars and the hemlocks. Their ponies provided fertilizer for flower beds. "Today, they're both in horticulture because we never made them weed," Lighty says.

Still, plenty of sweat has gone in to the garden. Lighty remembers digging trenches for daffodils that would erupt from beneath a ground cover of native pachysandra. Today, the plot is a dependable source of color and vitality in spring – and green throughout the year. "It's a lot of work – but when it's done, it's done," he says.

Although he's devoted vast hours to weeding – "it's a vanity of mine" – Lighty designed his garden so there's less maintenance as both he and the property mature. He shuns cedar chips from home centers, preferring to mulch with pine needles hauled down from his vacation home in the Adirondacks. "I hate store-bought mulch," he says.

He also chops several tons of leaves each year and applies them to beds in his continuing war to protect the good plants and keep unwelcome volunteers out. After decades of vigilance, he recently declared victory over chickweed. He eliminates other intruders with judicious a spritz of herbicide. "The secret is very low pressure," he confides. "A single squirt in the center of the plant will seal the weed's fate."

Because he is captivated by growing things, Lighty finds himself contemplating what not to add to the garden these days as much as what he will cultivate. "Sally is the one with the discipline to maintain the open vistas," he says. "I'm the guy who walks around with a plant, looking for a place to plant it."

Gem-like plants and creeping loosestrife adorn the dooryard garden

He's fond of flowering species such as the purple-bloomed Aster laevis, known as Bluebird, descended from a plant Lighty found in Connecticut. But his discerning eye sees beauty in the striped leaves of hosta and the twisting, zebra-like bark of the Clethra barbinervis. "Both Sally and I love textures," he says. "They delight us all year round."

Although it's difficult to find such unusual plants at garden centers, Lighty notes many species are available through mail order catalogs. "They're great sources, although the plants are small," he says. "But that's OK if you take the attitude of just planting them and watching them grow."

Exploring other gardens is a lifelong passion for Lighty. The nearly untended and all but unsung Crowninshield Garden at Hagley's Eleutherian Mills tops his list of inspiring places. Moved by its beauty, he wept when he first beheld the garden, landscaped around the iron and stone of a factory knocked down by a gunpowder explosion in 1890. "It is one of the most ethereal gardens in the world, just incredibly romantic," he says. "I thought, 'My God, what a place for a fashion shoot!'"

Ordinarily, Lighty doesn't care for artfully arranged ruins or otherwise contrived gardens for the same reason he frowns on declawing cats. "It's jarring and unnatural, an exclamation point on the landscape," he says. Still, he confesses an affectation of his own, a 25-year-old ginkgo tree by the swimming pool. By meticulously breaking off the long shoots, he tricked the tree into growing into a pure, straight oblong post. "It's a green telephone pole," he says.

Some times, the sweetest pleasures are the smallest, as in the crocus planted by the patio, the first delicious bonbon of spring. Inside the house, Lighty is now growing Wilson lemons and key limes, his latest horticultural infatuation.

"All gardeners become fascinated by one thing or another," he says. "I call this my citrus phase."