Horticulture isn’t a vocation filled with aha moments, but Harold Pellett was well-suited for its deliberate pace.

A quiet, patient man of subtlety and dry humor, Pellett spent 30 years as a professor at the University of Minnesota and a leader in research at the Minnesota Landscape Arboretum and Horticulture Research Center. He died July 24 at age 76.

“His motivation was to bring new, improved hardy plants for gardeners in cold-zone areas,” said Nancy Rose, a research scientist who worked with Pellett for a decade in the 1990s and is now editor of Arnoldia magazine at Harvard University. “He widened the color palette.”

Pellett bred and evaluated nearly 40 varieties of large trees, small flowering trees and shrubs, but is most known for 14 colors and varieties of azaleas. He introduced the Northern Lights azalea in 1978 and expanded the original pinkish-mauve hues to white, lemon yellow, peach and lilac.

“We can thank Harold for such beautiful spring flowers,” said Steve McNamara, at the University of Minnesota Horticulture Research Center. “To this day at the arboretum, the azalea beds stop people in their tracks.”

Pellett’s surprising discovery with colleagues is that crossing plants from the northern and southern zones results in a plant that in its second generation is hardier than the original northern parent, said Peter Moe, director of operations at the arboretum. “He really had a major impact on the whole nursery industry,” Moe said.

The love of plants was bred into Pellett. His grandfather, parents and older brother also pursued horticulture, as does his son Darwin, a gardener and crew leader at the arboretum. He won scores of professional awards but never made a fuss over any of them.

“He sometimes disappeared for a day or two at work without saying where he was going, and then we’d hear about his latest award when someone from the arboretum stumbled upon an article in a trade journal somewhere,” McNamara said.

Pellett’s taciturn demeanor sometimes gave way to mischief. His brother Norman recalled when Harold, as a boy, dropped an earthworm into their father’s tobacco tin for hand-rolled cigarettes. “It didn’t taste good as part of dad’s tobacco smoke,” said the older brother, “but Dad took most of these pranks in good humor.”

When McNamara first started working with Pellett, the pair took a drive through the arboretum to look at the maple collection when they suddenly saw a bear standing in a clearing. “I fought off the instinct to jump from the truck and flee and shot Harold a sideways glance of veiled terror,” McNamara said. “He was grinning from ear to ear. They were filming an ad complete with trainer, lights and bear snacks. He knew it but never let on.”

At home, Pellett, his wife, Shelby, and their six children continued their love of plants and nature. They had four acres of garden space in Minnetrista and a greenhouse. “He and my mom would sell vegetables and annuals from the greenhouse out of their home,” said daughter Cindy Jacobs of Eden Prairie. “I would wait on customers. I learned math by counting change.”

Now Jacobs takes her own children to the arboretum a couple of times per year. “As a kid, I’d be running around the arboretum while Dad worked, catching tadpoles in the pond, and my mom and brother pointing out his Cardinal Red dogwood or azaleas in bloom,” she said.

Gardeners can still buy many of the varieties Pellett cultivated, though few know of the work behind them. It can take 10 to 20 years from initial breeding and, out of 10,000 seedlings, only one may reach production.

He is survived by his wife and all six children, 13 grandchildren, a great-grandchild and three siblings. Services have been held.