Plant entries have doubled in the last decade, to almost 6,000, according to the Pennsylvania Horticultural Society, the show's producer. PHS president Drew Becher attributes this to "younger competitors, high school garden clubs, and college students who've had success growing herbs on the kitchen windowsill, and garden clubs and social media spreading the word.
"It's become sexy again," he said.
And yes, the show still has idyllic landscapes and flower arrangements, speakers on topics ranging from garden photography to unusual houseplants, and row upon row of garden-related vendors.
But there are signs of new energy everywhere.
There's more emphasis on organic gardening, native plants, and wildlife habitats, and a growing culinary presence under the rubric "Garden to Table."
There's more space devoted to floral design and Iron Chef-like flower-arranging competitions with audience members as judges. And exhibitors on both the floral and landscape sides say PHS is encouraging them as never before to be creative.
"Last year, they assigned specifics, and everybody was not quite comfortable with that. It was much looser this year. They wanted to see something modern," said Michael Petrie of Michael Petrie's Handmade Gardens in Swarthmore, who won 2013 Best in Show/Landscape.
This year, MODA Botanica did a modernist take on the English moors, Schaffer Designs riffed on "Jack the Ripper," and 15 members of the American Institute of Floral Designers came from around the country (and England) to interpret the crown jewels using pine cones, seeds, raw cotton, and other plant material.
"Floral design has become much more important since Drew got here [in 2010]," said Ron Mulray, of Philadelphia Flower Co.
Becher is also interested in cultivating the next generation of gardeners, especially local high school and college students, whose exhibits are already show favorites.
Temple University Ambler launched "Wilde! Cultivating wonder in everyday places," an ode to spontaneous wildness in every form, even weeds.
"If a plant comes into your garden, you could choose to accept that plant and let it be. Seriously," said junior Shannon Kelly, who helped design the exhibit.
The Williamson Free School of Mechanical Trades in Media chose "Horticulture in 18th-Century America" as a theme, emphasizing the horticultural interplay between the colonies and England.
Students researched noted Philadelphia botanist John Bartram and other early seed dealers, such as David Landreth and Bernard McMahon, and re-created an 18th-century nursery with native plants that grow well in today's home gardens.
"Bartram was able to share with the rest of the world what America had to offer," senior Tom Bongiorno of Ridley said.
Kirk Brown was doing some sharing - as Bartram - at the Gardener's Studio, next to Williamson's exhibit, on Saturday. Dressed in an 18th-century costume sewn by his wife, Sara, the Orefield, Pa., actor and garden designer told a rapt audience that Bartram's plant expeditions throughout eastern North America were about "preserving God's world."
The biggest "new energy" at the flower show, which raises $1 million for PHS programs, is also its most controversial - the increasingly high-tech central feature, which critics dismiss as too much Disney and not enough flower show.
This year, it's Big Ben with palace gates and a fast-paced video with rock music, flashing lights, and iconic British images such as the royal family and the Beatles.
"Definitely a reflection of the times. To be relevant, the show has to touch more people than me," said Betsy Szymczak, a "hardcore horticulturist" from Boston who pronounced the central feature "interesting."
Carol Heim, a retired teacher and gardener from Haddon Heights, had the opposite opinion.
"Before I came, I was hoping, 'Please, don't have loud music, any music, the whole time' - and they have it," she said.
To watch a video of the members' preview at the Flower Show, go to www.philly.com/flowershow2013
Contact Virginia A. Smith at 215-854-5720