by Ned Barnard and Pauline Gray

The following is the second in a new series of columns by Ned Barnard and his wife Pauline Gray. Barnard is the co-author of several books on trees, including “Central Park Trees and Landscapes” and “Philadelphia Trees: A Field Guide to the City and the Surrounding Delaware Valley,” which he wrote with Paul Meyer, former director of the Morris Arboretum.

The ginkgo tree with its stiff, spiky branches, corky bark and spectacular yellow, fall foliage, is quite common along the avenues and streets of Chestnut Hill, Wyndmoor, Mount Airy and Germantown. It is the sole remaining member of an ancient arboreal order with a lineage that can be traced back nearly 250 million years. Only a single ginkgo species is known today, but several species coexisted with dinosaurs and were widespread in both hemispheres. By the ice age’s end, however, just a few wild trees were left in eastern China. Fortunately, Buddhist monks planted them around their monasteries and temples, and today, some of these compounds are shaded by ginkgos more than 1,500 years old.

The ginkgo first arrived in Philadelphia in 1785 when William Hamilton, a wealthy Philadelphia horticulturalist, imported several, one of which still stands in Bartram’s garden by the Schuylkill River. The ginkgo, tolerant of difficult urban growing conditions, is now found in cities the world over.

Ginkgo seeds are deemed by some to be delicacies. After collecting the fruit-like seeds when they drop to the ground in fall, some Asian people peel and either roast or boil them. In spring, the ginkgo bears inconspicuous male cones and female ovules on separate trees. Male trees are preferred because the females’ flesh-coated seeds become malodorous as they turn from green to yellow and drop to the ground.

Most Hill ginkgoes are males, but a few females are around, including one standing next to the entrance of the Evergreen Avenue parking lot behind Bank of America. It produces hundreds of seeds, which when crushed on the sidewalk, create a smelly, gooey, slippery obstacle course for passing pedestrians. Curiously, no rodents or birds seem attracted to the seeds.

It’s likely, however, that carrion-eating dinosaurs once considered these squishy, rotting globules reeking of butyric acid, which smells like vomit, tasty treats and spread seeds far and wide.

When dinosaurs disappeared and glaciers scoured parts of the Northern Hemisphere, worldwide ginkgo populations greatly diminished. Now humans have taken over the job of spreading the ginkgo around the globe once again.