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Rare in the wild, trees now common in cities

Unique ginkgoes are living fossils

by Adrian Higgins

The Washington Post

This fall, the fan-shaped leaves of the ginkgo tree will turn a golden yellow, and in the silence of the night, the tree will offer a little arboreal tremor and drop its entire canopy in a total release of its unique and primal foliage.

The phenomenon leaves a knobbly, naked tree and a pavement of gold. An old ginkgo can have as many as a million leaves.

Some people dislike the ginkgo, mostly for its smelly and messy fruit, others because it is not a native plant.

Sir Peter Crane loves it. In his new book, “Ginkgo,” he ties together the botany, history and lore of a plant that is unique on Earth.

“Unique” is an overworked adjective, but it applies to the ginkgo. Among seed-bearing plants, botanists know five groups. Four are the vast tribe of flowering plants, from maples to rice; the conifers; the palmlike cycads; and an obscure clan called the gnetales, whose most famous member is the ephedra.

The fifth group is represented by the lone surviving species of the living fossil we know as Ginkgo biloba.

It is this unbroken connection to a world dating back tens of millions of years that gives the ginkgo a singular appeal, imparting a frisson at the thought that among us today is the same plant known to the dinosaurs.

Among its oddities:

It behaves like a conifer but it has leaves, not needles.

Individuals are either male or female (far more common is the hermaphroditic flower).

Its pollen, in the act of fertilization, act as swimming sperm. This phenomenon is also seen in other primitive plants such as ferns and is linked to the fact that they emerged from a wet environment.

The swimming abilities of the spermatozoids were discovered by teaching assistant Sakugoro Hirase in a female ginkgo that is still growing at Tokyo University’s Koishikawa Botanical Gardens, available for public viewing. The ginkgo has been the official tree of Tokyo since 1996.

Old trees in general remind us of our own limited life span, but the ginkgo “epitomizes that in an even greater way because it’s a member of a lineage going back 200 million years,” said Crane, a paleobotanist and dean of the school of forestry at Yale University. When he served as director of the Royal Botanic Gardens at Kew, southwest London, he knew as a venerable friend a ginkgo that was one of the few original Kew trees, the “Old Lions” dating to the mid-18th century. It was one of the first ginkgos brought to the West from China.

In spite of its tenacity, the ginkgo has only barely survived in the wild. Closely related species — known only as fossils — ran their course. Ginkgos once grew around the world, but the tree was erased from all but Asia by glaciers and, Crane believes, the extinction of animals that spread its seed.

“When the last great southward push of the ice had retreated, ginkgo was barely hanging on, perhaps only in protected valleys scattered across eastern and south-central China,” he writes. “By the time modern people arrived in that part of Asia, perhaps 50,000 years ago, ginkgo was already a relic.”

So, as Crane points out, the lone surviving species of ginkgo came to rely on the lone surviving species of hominid — us — to save it. Nurtured for its sacred symbolism and the practical value of its edible nuts, the tree would take on a greater role in modern times.

Ginkgos grow tall but don’t spread much, flourish in tight quarters and endure pollution. These qualities make them useful in that most unprehistoric of places — the city. This has been their salvation.

They are free of disease and pests (presumably because none coevolved with them), and this in itself is a big deal when you consider the afflictions of elms, oaks, maples, lindens and ashes — and the effort, money and poisons expended to protect them. Ginkgos deserve a following on the simple basis that they are attractive and useful additions to our landscapes.

The fruit around the nuts is messy and malodorous and detracts from the tree’s value along a street or next to a patio. Its sex is not revealed until it reaches fruiting age, about 25 years.

Ginkgos, thus, have a place on our tree lists, especially as street trees so that we can see out the growing season in splendor.

In 1982, Crane was among a small team of paleobotanists who came across fossils of an extinct ginkgo in a fossil-rich area of North Dakota. Their ginkgo, a species now bearing Crane’s name, was pegged at 57 million years old. The discovery raises questions, surely, about the wisdom of viewing plants as “native” or “alien,” a distinction that preoccupies a lot of people these days.

As much as we have saved the tree, we have the capacity to destroy it.

Crane pointed out that we can take a tree that has stood for centuries “and cut it down in a morning.” He spoke of an awful episode in Washington in February when a contractor for the National Park Service cut down the city’s largest ginkgo by mistake. Distinctive baby leaves now sprout around the stump’s edge, and it may yet survive.