A Mystery Tree Grows in Princeton

There's a small tree I've been encountering occasionally in Princeton woodlands, and no one thus far has been able to figure out what it is. I discovered it years ago, while preparing an ecological assessment for the Friends of Rogers Refuge. Over the past couple years, I've encountered a few younger versions in Herrontown Woods, and was finally moved to learn its identity. I thought it would be a simple matter to send some photos around to people particularly knowledgeable, and an answer would quickly be forthcoming. But no. This is turning into a botanical version of Stump the Stars.

I first saw it while taking that dirt road into Rogers Refuge, long known as a birding mecca just below the Institute Woods. The photo shows it in full bloom, though you have to look really hard to see the clusters of small flowers.

As someone schooled in botany, my experience of driving is different from most people's. While keeping an eye on the road, a botanist is also keeping an eye on the texture, shape and color of vegetation streaming by. You learn to identify trees in an instant. Their seasonal bloom or fall color can make it easy, but even their overall growth form--their body language--can be enough. The army fatigue bark of sycamores is distinctive, running up a valley in winter. Or the blotch of blue a Princess Tree's blooms make among the trees lining a highway. 

Over time, what for most people registers only as a blur of greenery becomes instead a language to be read. Driving along, reading the language of the roadside out of the corner of my eye, I'll very occasionally see something outside of my vocabulary of plants. Sometimes I pass by a given spot many times before a particular flower or growth shape catches my eye and I just have to stop to take a closer look. 

That's how this mystery tree first caught my eye, while driving into Rogers Refuge some years back in the second week of May.

It has the kind of bloom that looks showy close up, but doesn't have much of an effect from a distance.

Though most seen elsewhere in town tend to be the size of shrubs, the specimen in Rogers Refuge is about 20 feet high, with a cluster of sizable trunks.

New growth is distinctive.

Fruits are red, and scarce considering all the blooms.

Mike Van Clef mentioned "another confusing non-native relative found at Jockey Hollow."

Bob Wells of Morris Arboretum sent a scholarly response, based on some but perhaps not all of these photos:

I have no doubt that this is one of the Aronias:

• Rosaceae flower
• Alternate, simple, elliptic leaf that comes to an acuminate point.
• Small, even, serrated margins
• Secondary veins disintegrate before reaching the margins

He referred to the texts by Dirr and Easton, particularly a quote from Easton: “Chokeberries remind us that scientific taxonomy is only the least imperfect of the tools that we have fashioned to help us classify and understand organisms”

I'd love to call it red chokeberry and declare the case closed, but the leaves don't look or feel quite like any red chokeberry I've ever seen.