The flower of the rare Emmenopterys henryii in Chestnut Hill. (Photo by Ken LeRoy)

by Ken LeRoy

Three years ago a friend asked me if I knew the species of an odd tree growing along the 8400 block of Seminole Ave, across from the Chestnut Hill West train station parking lot. Odd indeed, because I didn't have a clue.

Growing out of a hedgerow between properties, this 40-foot tree with light gray, finely fissured bark and large, simple, Magnolia-like leaves with red petioles was totally new to me. Instead of researching using a tree identification key, I took a short cut and called Paul Meyer, director of the Morris Arboretum.

"Paul, there's a tree on Seminole Ave that I don't know."

His immediate response: "Emmenopterys henryii."

Thanks Paul! That's a new one for me! New, because it is so rare under cultivation that the Morris does not have one, nor Swarthmore's Scott Arboretum. Although they have some young ones coming. Longwood Gardens also has some young trees.

Found in Badong Province in the mountains of central China at 2 -4,000 feet elevation by Augustine Henry in 1882, the Hsiang Ksu tree, as it is known in China, was collected and introduced in 1907 by the famed plant collector Ernest "Chinese" Wilson who called it, "One of the most strikingly beautiful trees in the Chinese forest."

According to Andrew Bunting, Curator of Collections at the Scott Arboretum of Swarthmore College, "Emmenopterys henyii is very rare in cultivation, most botanical gardens and arboretums don't grow it, and extremely rare to find a flowering specimen."

The first sporadic flowering in Europe occurred at Wakehust Place in Sussex in 1987. Kalmthout Arboretum in Belgium reported flowering in 2009, and built a viewing platform for visitors. I noticed sporadic flowering at the top of the crown in 2013, but this year the tree is in full, spectacular bloom from the top of the crown to the bottom. The flowers occur in a panicled inflorescence, with the creamy white, tubular individual flowers opening one at a time over two to three weeks. Showy white bracts highlight the scene and remain persistent, which is where the tree gets its name, Emmenopterys - "Persistent Wings." The flowers have a Gardenia-like fragrance, that one has to inhale to appreciate. The perfect flowers, having both male and female parts in the same flower, should produce seed this year if pollinated. I have observed butterflies and bumble bees visiting the tubular flowers, and speculate that the fragrance may attract nocturnal moths.

Horticulturists have speculated that warm, dry summers followed by a cold winter may stimulate the tree to flower. So, at least this past winter was beneficial in some way.

I have not spoken with the owners and have no idea who planted the rare tree, but it must have been a very knowledgeable, well-connected plantsman. Perhaps the tree is 60 - 80 years old, that's only a guess. It is easy to admire the tree from the sidewalk along Seminole Ave.

Ken LeRoy, ISA, is a Certified Arborist, teacher and photographer. He is also the founder of the Facebook Page: Arboretum Philadelphia, dedicated to posting significant trees of the Philadelphia metropolitan region. A community page where people can share the special trees in their neighborhoods.