Lying down in the back of the moving car, watching trees ... almost home, suddenly I saw one I'd never noticed before: in front of the rectory of St. John's Catholic Church, at the north end of Townsend Common, a ten-foot Ginkgo.

Ginkgo biloba is the only remaining member of the phylum Ginkgophyta, which predates the dinosaurs. During the saurian ages (hundreds of millions of years) Ginkgoes spread throughout what is now Asia, Europe and North America. About seven million years ago they disappeared from North America; after 2.5 million, from Europe. In China they survived into historical times cultivated in Buddhist temple gardens; from there they were transported to Japan and Korea. In 1691, the German physician-botanist Engelbert Kaempfer discovered the Ginkgo in Japan; he brought seeds back to Holland with him.

The tree initially grows slowly, in a narrow column; the one here, 20 feet tall, is probably about 11 years old, and is just starting to widen, with a spread of 13 feet. It's also losing its central leader, which is not uncommon: older trees can develop several trunks. Eventually it may reach 100 feet tall, with branches sometimes growing in odd and picturesque shapes.

Leaves grow alternately along the trunk and main branches, and in clusters from little projecting spurs. Slightly leathery, the leaves have a broad fan shape, usually two-lobed — resembling a three-inch-wide version of the leaflets on a Maidenhair fern. Ridged leaf veins fan out from the base, too, without any midrib — a primitive vascular pattern, unique to the Ginkgo. Carried on a three-inch petiole (leaf-stem), these leaf-fans flutter in the slightest breeze. Green (sometimes yellow-green) summer foliage turns yellow in fall — occasionally quite spectacularly. Then the leaves all fall together, within 24 hours.

Not picky about soil, resistant to fire, diseases, insects, and air pollution, Ginkgoes grow well in cities. They even survived nuclear bombs in Hiroshima.

The trees are dioecious: each bearing flowers of one sex. Like conifers, they release pollen profusely, depending on wind for dispersal. Achoo! — guess I won't plant one. Nevertheless Westerners prefer male Ginkgoes, because on the female, the fleshy seedcoat contains butyric and hexanoic acids, which smell putrid and are dangerous. In the Orient, people consider the nuts (carefully prepared) a culinary delicacy.

Ginkgoes are so unusual, I've always been fascinated by them. Why did it take me so long to see this one?

• The Ginkgo Pages - a huge site, with fascinating detail, photos, and links, by Cor Kwant, a Ginkgo enthusiast in the Netherlands.
• A Tree Preservation Project at the University of New Hampshire, held October 23, 2002, to restore a mature Ginkgo.
• RUFF: Shade Trees: Large: Ginkgo. The Roseville Urban Forest Foundation in California, provides trees for residents and businesses to plant. They say their Ginkgoes are sterile, with no reproductive parts. I'd like to find out where to get them!