After 17 years with the PHS Philadelphia Flower Show, Sam Lemheney has accumulated a long list of ideas to reference when it’s time to pick a theme for the esteemed annual event. This year’s Riviera Holiday had been on that list for a while, but a partnership with the Principality of Monaco, where a certain Philadelphia actress-turned-princess once lived, elevated the exhibition entirely. “Grace Kelly had a long history with the Flower Show,” says Lemheney, chief of shows and events. “She was an exhibitor, a judge and visited a number of times over the years.” Amid the clouds of lavender plants and rows of Italian cypress trees is the Princess Grace Rose Garden, inspired by the famed garden of the same name in Monaco, with a replica of Kelly’s wedding dress as its centerpiece. PHS worked closely with the Prince Albert II Foundation for its Gardening for Biodiversity Symposium on March 4. Says Lemheney, “We want to change the mindset about gardening, that it can be sustainable and beautiful at the same time.” Feb. 29 - March 8, Pennsylvania Convention Center, 1101 Arch St., theflowershow.com