THE Perennial Plant Conference

John Friel

Another Swarthmore perennial conference, one of horticulture’s few yearly rituals that still lures me back even in retirement, is history.

Like the Perennial Plant Association, this event started in 1983. I first attended sometime before 1990 and have rarely missed it since. I was honored to present once and later to join the planning committee. Like the Philadelphia Flower Show, another one I seldom skip, some years are better than others. But I’ve never left thinking my day could have been spent more profitably elsewhere. 

Let’s meet two of this year’s presenters. 

Tony Spencer is a Canadian writer, photographer and landscape designer. Known as “The New Perennialist,” he’s a sought-after speaker in America, the UK, Europe and Asia. He’s won PPA landscape design awards. His website, thenewperennialist.com, urges “Do try this at home.” 

Tony’s landscapes are often called “wild-ish.” He calls them “designed plant communities inspired by nature.” In “Wildscaping: Plant-driven Landscape Design,” he showcased his home in Ontario as “an open experiment in naturalistic gardening.” The heavily planted property comprises a green roof cabin addition, swales, a pond and multiple beds that “flow out into the greater landscape.” 

Result: A controlled riot of color, form and texture in all seasons and stages. Happily, the spectacular images included Latin names, very welcome for many of the unusual species profiled. More speakers should be so thoughtful. 

Tony took up designing in his 40s after discovering Dutch plantsman Piet Oudolf, at whose name naturalistic gardeners genuflect. If you’re unfamiliar with his oeuvre, conjure up the short film “Five Seasons: The Gardens of Piet Oudolf.” When Tony eventually got to work with the master, he said, “I have read over the shoulders of giants.” 

His website describes “a collective dream to re-wild our nature-deprived urban worlds.” But he cautioned us not to confuse “wildscaping” with “rewilding,” a very different discipline. 

Sam Hoadley is Manager of Horticultural Research at Mt. Cuba Center, a luscious 1,000-acre du Pont estate turned public garden in Delaware. There are 68 acres of gardens and 3 miles of scenic walking trails, all focused on the aesthetic and environmental value of native species. 

Mt. Cuba conducts rigorous four-year trials of multiple genera. Sam highlighted two: The underused, underrated vernonia (ironweed) and solidago (goldenrod), which he stressed does not­—repeat, not—trigger allergies. 

Vernonia was a candidate for the PPA’s Perennial Plant of the Year. The Garden Club of America has declared V. lettermannii Iron Butterfly (introduced by Steve Castorani of North Creek Nurseries) its plant of the year for 2026. Here’s hoping increased attention means increased usage. 

Trials are irrigated and fertilized for just one year. The goal, Sam said, is to identify “low-input, high-impact” garden plants. Data are gathered weekly, with plants evaluated on a 1-to-5 scale. A 5 score = “virtually perfect.” 

Beauty isn’t enough: environmental value also counts. Vernonia supports multiple pollinators, including Monarch butterflies. Consider planting it with asclepias and don’t baby it—it’s called “ironweed” for a reason. Said Sam, “People tend to treat it too nicely.”

Top performers of 45 tested: V. angustifolia Plum Peachy from Tony Avent, Plant Delights Nursery; and two hybrids, Summer’s Surrender and Summer’s Swan Song, bred by Dr. Jim Ault, Chicago Botanic Garden. 

Solidago also draws multiple pollinators, including bumblebees, wasps and small butterflies. Attention birders: kinglets and warblers visit, too. Sam said that while some forms sprawl, “there are plenty of well-behaved, clump-forming varieties.” Careful selection can yield six-plus months of bloom. 

Top performers of the 70 taxa tested included the familiar Fireworks, which Sam cautioned tends to spread. Others scoring from 4.5 to 5 were S. sphacelata Golden Fleece and S. drummondii. 

Trial results are available online. Vernonia is posted now; solidago will appear in January.

Fast-forward to October 2026. You and 599 fellow well-fed plant nerds, professionals and keen gardeners are in a comfortable auditorium, surrounded by the beautiful Scott Arboretum. The world’s finest plantspersons—public gardeners, designers, landscapers, breeders—have come to entertain you. It’s pretty sweet.

Can’t make it? It’s Zoomable, via Longwood Gardens Continuing Education. 

My apologies to the other four speakers that This Space isn’t more spacious. Rather than relegate their fine presentations to mere snapshots in words, we’ll give them their due next month. GP

John Friel is a freelance writer with more than 40 years of experience in horticulture.