"Think of all the careers horticulture is competing against. We need to make it sexier and more relevant in a highly competitive market," said Paul B. Redman, director of Longwood Gardens in Kennett Square and a strong supporter of a four-year remedial campaign outlined in the letter.
That campaign calls for:
A scientific study of the problem to support with numbers what backers believe to be true.
An education plan outlining how horticulture can be integrated into K-through-12 curriculums and promoted on college campuses.
An advocacy and marketing strategy to raise public awareness of horticulture's importance and of career options.
"We have to come up with a game plan. Period," said Redman, who has been in horticulture for three decades and who still has to define for people what that means.
Which may be the first hurdle this initiative faces - besides funding, which is still an unknown. And it's laughably elementary: What is horticulture, anyway?
By the book, horticulture is the art and science of growing fruits, vegetables, flowers, and ornamental plants.
More often, in the public mind, "it's a guy with a pickup truck and a lawn mower, a low-paying job requiring manual labor and no college degree," said Mary H. Meyer, horticultural science professor at the University of Minnesota and, as president of the American Society for Horticultural Science, a critical force in the campaign.
Meyer cites other career opportunities: plant breeding; greenhouse and food production; the cut-flower, landscape, and nursery industries; public gardens, parks, and sports turf; research into global climate change, plant pests, and diseases, water quality, biofuels, and food safety and security; and the psychological and physiological benefits of plants.
This crisis is not unique to the United States, as Meyer discovered during a teaching stint in England over the summer: England, the world's horticultural powerhouse, faces the same problems.
In a report in May, the Royal Horticultural Society decried "an alarming shortage of skilled professionals" in horticulture jobs, posing "a threat to Britain's economy, environment, and food security."
Horticulturists in both countries say the crisis has been building for decades, greatly influenced by the globalization of the food and flower trades, the population shift from farm to city, and the loss of personal connection to the land.
"When do most people get interested in plants now?" asked Richard Marini, head of Pennsylvania State University's plant science department. "Usually, when they buy a house, and by then, they're out of college."
(In another sign of the times, 18 months ago at Penn State, the agronomic and turf scientists merged with the horticulturists to form the plant sciences department.)
Matthew Bond, 21, a plant sciences major at Cornell University, found his future the old-fashioned way: He grew up in farm country in Ogdensburg, N.Y., where his father and grandmother were enthusiastic gardeners.
Bond, an officer of the National Junior Horticultural Association since 2009, is worried. The group's membership has plummeted from 1,000 in the '60s to half that number 15 years ago to 300 today. He suggests today's heavily scheduled kids have no time for hobbies like gardening. "They don't even go outside," he said.
But Bond is encouraged by the surge of interest among young people in urban farming and organic food production, a trend that could inject much-needed energy into horticulture.
Pauline Hurley-Kurtz, chair of the landscape architecture and horticulture program at Temple University, Ambler, says that though student interest in traditional horticulture - ornamental shrubs, trees, and plants - is holding steady, practical courses on growing food, storm-water mitigation, native plants, landscape restoration, urban arboriculture, even beekeeping, had become extremely popular over the last two or three years.
"We're doing much more environmental horticulture here," Hurley-Kurtz said. "It's the way of the future, but we still need professionals who have a background in horticultural science."
There's the challenge.
"There's nothing sexy about plant science until you make it so for kids. Once you do, they're hooked," said Jessica McAtamney, who teaches environmental science and urban gardening at W.B. Saul High School in Roxborough.
Hydeia Brown, 17, from Germantown, could be the poster child for an idealized horticultural future, one that includes not just more practitioners, but more diversity, too. An environmental science major in Saul's horticulture program, Brown wants to make a career out of plants.
"I love science," she said in a phone interview from Morris Arboretum in Chestnut Hill, where her class is photographing and cataloging the Latin botanical names of pitch pine, American holly, and other trees.
Brown, whose family left their South Carolina farm to move north before she was born, wishes "other kids would come out and experience this. Not a lot of them know about the outdoors. They like electronics and stuff like that."
That mind-set is just one obstacle to a horticultural turnaround, which, if it happens, could take 20 years. But many believe a long-term commitment is critical.
For Douglas C. Needham, education department head at Longwood, it's also personal. "I'm passionate about this," he said, "and I don't want to see the art, science, and craft of horticulture die out."