Ginkgo

Three nuts in a golden casket

Kaifeng, early in the eleventh century. The capital of Song China has no duck-foot trees.¹

Li Zunxu, who is married to a princess, means to change that. He has the trees brought up from the river country south of the Yangtze and planted at his mansion.^{1, 2}

One autumn the trees bear fruit for the first time, and the whole picking is three or four nuts. They go to the emperor in a golden casket, before the great lords of the court even know what they are. The emperor sends back a hundred in gold.¹

In the south it had a homely name, duck-foot, for the shape of its leaf. Sent north in crimson bags as tribute, it was prized in the capital under a grander name. It looked like a small apricot with a pale stone, so they called it silver apricot.^{1, 3}

Years went by and the nuts grew thick on the branches. The master of the house, famous for his hospitality, handed them out like pearls. One who got some was the poet, historian and statesman Ouyang Xiu, and he told the whole story in a poem.¹

The poem recalls grapes and pomegranates. They must have cost as much when the envoy Zhang Qian first brought them from Central Asia. Now they grew at the foot of every hedge and along the tops of walls. People's feelings drift with the times, so the nut's beginning should be written down for later ages to know. This too is the historian's method.¹

The nut was new to the court. The tree was one of the oldest living plants on earth, its line barely changed in at least 200 million years.⁴

A thousand nuts and you die

By 1578, when the Ming herbalist Li Shizhen finished his Bencao gangmu, the nut had a third name, white fruit.³

The tree flowered in the night, he reported, and the flowers dropped at once, so hardly anyone saw them. A female would bear if a male grew within sight of her, or if she stood beside water. Failing that, you could bore a hole in the tree, push in a plug of male wood and seal it with mud.³

He prescribed the cooked nuts for wheezing, coughs and passing water too often, and the raw ones, chewed to a paste, for chapped hands and feet. He warned that too many left you bloated and dazed. One older book said that whoever ate a full thousand would die, and told of starving people who once ate their fill of the nuts in place of rice. The next day they were all dead.³

A herbal of the 1300s had already warned that children who ate too many went dazed and had fits.³

In Japan the warnings came true. About seventy reports describe ginnan poisoning, named after the nut. It broke out now and then in the hungry years between 1930 and 1960, mostly in infants. The telltale sign was convulsions, and more than one in four died.⁵

In 1985 a team of pharmaceutical scientists in Hokkaido found the cause. They fed fractions of the kernels to guinea pigs, and within 40 minutes the animals' legs were paralysed and their backs arched in convulsions. The culprit was a compound that blocks vitamin B6, never before found in a natural product.⁵

The doctor's spelling

In September 1690 a German doctor named Engelbert Kaempfer reached Nagasaki, the only Japanese port open to Dutch and Chinese ships. He was physician to the Dutch East India Company's post on Dejima, a small artificial island in the harbour that he called a jail. Twice he went to Edo, to the court of the shogun Tokugawa Tsunayoshi.^{6, 7}

In a Latin book printed in Germany in 1712, he described a nut tree with a leaf like a maidenhair fern.^{8, 9} It grows as big as a walnut tree, and its bluish green leaves, deeply notched in the middle, turn reddish yellow in autumn. The fruit looks like a damson. Its white flesh is very harsh and clings so hard that the nut can only be freed by letting it rot and stirring it about in water.⁸

The kernel inside is sweet as an almond, with a harsh edge. Eaten after a meal, the kernels were said to ease a belly swollen with food, so no formal banquet ever left them out of the dessert.⁸ Li Shizhen had blamed too many of them for exactly that swelling.³

Kaempfer headed the entry with the two characters for silver apricot, and beside them their reading. Ginkgo.⁸

It should have been Ginkjo. A Japanese picture dictionary of the time reads the characters as ginkyō, and everywhere else Kaempfer wrote that sound as kio or kjo. His own notes from Japan already say Ginkgo, so no printer was to blame. The Kaempfer scholar Wolfgang Michel calls it a small mistake, perhaps made over a glass of liqueur, or on one of those sticky Kyushu summer days when tiny details stop mattering.⁹

In 2015 three researchers offered another answer. Kaempfer was faithfully writing names down the way his young assistant, Imamura Gen'emon, said them, in the old Nagasaki dialect.¹⁰

Either way, it stuck. In 1771 Linnaeus took it from Kaempfer's book and made it Ginkgo biloba, the two-lobed ginkgo.¹¹

One leaf, or two?

The tree reached Europe from Japan about 1730, at the botanic garden in Utrecht, and Kew had one by the 1760s.^{12, 13}

In September 1815 Johann Wolfgang von Goethe, then 66, was in Frankfurt as the guest of his friend Johann Jakob von Willemer, a banker.^{14, 15} Willemer's wife Marianne was thirty. Born in Austria, she had been an actress, singer and dancer, and had come into Willemer's house at fifteen as his foster daughter. She had married him the year before. She was Goethe's love in old age.^{14, 15}

In mid-September Goethe sent her a ginkgo leaf from town. The art collector Sulpiz Boisserée was staying with him at the Gerbermühle, the Willemers' mill house outside the city. He wrote it up in his diary on the 15th. The leaf was "a symbol of friendship", and a verse went with it. It said nobody could tell whether this was one leaf dividing into two, or two joining into one. "We sat on the balcony in the lovely warm evening air."^{15, 16}

The verse grew into a poem, its first version dated the 15th too. The leaf of this tree from the East holds a secret meaning, it begins. Is it one living thing that has split in two, or two that have chosen each other and are known as one? Can't you feel in my songs, the poet answers, "that I am one and double"?¹⁵

He printed it in 1819, as "Gingo biloba", in the Book of Suleika of his West-Eastern Divan. Some of the Suleika poems were Marianne's own, among them the songs to the East Wind and the West Wind. Neither of them said so in public. She kept the secret for more than forty years and told it, shortly before she died, to the scholar Herman Grimm.^{14, 15}

One and double, after all.

Swimming sperm in the shogun's garden

Tokyo, 9 September 1896. At the Imperial University, Sakugorō Hirase is cutting open young ginkgo seeds one after another, looking for something he has only ever seen in prepared slides.¹⁷

Hirase was no trained botanist. Born in Fukui in 1856, he had taught drawing, and in 1888 the university hired him to draw plants. He taught himself to make microscope slides, and in the ginkgo's pollen tubes he found an oval body with a coiled band like a snail's shell, fringed with fine hairs. In April he told the Tokyo Botanical Society it was a sperm.^{17, 18} A sperm should swim.

On 9 September he saw them swim, the first swimming sperm ever seen in a seed plant.^{17, 18} Mosses and ferns have swimming sperm and flowering plants do not, and the ginkgo sat between them. Along with Seiichirō Ikeno's cycad sperm that same year, it was Japan's first contribution to modern biology.^{18, 19}

The next year Hirase left the university. He taught in middle schools and died in Kyoto in 1925. His tree, a big female about three hundred years old, still stands near the middle of the university's garden at Koishikawa, which began in 1684 as the shogun's herb garden.^{17, 18, 19}

Ten million trees in South Carolina

In America, meanwhile, ginkgo had become a favourite street tree from Boston to Washington. In the 1920s and 1930s the female trees came of age. Their fallen seeds, crushed underfoot, smelled of vomit, and the gardening books reached for every word they had. Disagreeable, evil, offensive, disgusting, repulsive, nauseating, abominable.¹²

The leaf's fortune was made in Germany. In the 1950s the Schwabe family firm in Karlsruhe began studying the tree. Its technologists worked out a twenty-step process that concentrates some substances up to twentyfold and cuts the unwanted ginkgolic acid twenty-thousand-fold. Schwabe protected the process with patents, and its first ginkgo medicine went on sale in 1965.²⁰

By 1982 there were leaf plantations at Bordeaux in France and at Sumter, South Carolina. By 1991 Sumter's 400 hectares held some ten million trees. It was "surely the largest Ginkgo forest on earth," wrote Peter Del Tredici of Harvard's Arnold Arboretum, "at least since the Paleocene."^{12, 20}

Machines stripped the leaves while still bright green, and ships carried them from Charleston to extraction plants in Europe. Sales there reached about 500 million dollars in 1988.¹²

From 2000 to 2008 an American trial, the Ginkgo Evaluation of Memory study, followed 3,069 volunteers aged 75 and over for about six years. Each took the extract or a dummy pill.²¹ What that trial and the others found is in the Research tab.

The five thousand years

An encyclopedia of diets gives ginkgo about five thousand years in Chinese medicine, for memory loss among other things. Supplement sites say millennia.²² A German university garden adds that its healing power was first written down in the famous "Handbook of Barefoot Medicine", in 2800 BC.²³

The barefoot doctors were real. They were village health workers in Mao's China, and the best known of their manuals came out in 1969.²⁴

The herbal behind the date is named after Shennong, a mythological ruler said to have tasted hundreds of herbs. It was written down about two thousand years ago and lists 365 drugs. Ginkgo is not one of them.^{22, 25}

The trail runs back at least to 1991, when Del Tredici wrote that ginkgo "is apparently mentioned" in that herbal, "dating from 2800 B.C." His source was a 1988 chapter by P. F. Michel and D. Hosford, and there the trail goes cold.¹²

In a 1986 French book the same Michel told of a ginkgo in Hiroshima's Peace Park, a few hundred metres from ground zero, that had survived the blast. Del Tredici repeated it, then tried to confirm it, and could not.^{12, 26}

Li Shizhen had put it plainly in 1578. Ginkgo only became known when the Song dynasty began, and for generations the herbal writers left it out.^{3, 25} A Yunnan herbal credited to a fifteenth-century doctor says to pound the leaves and rub them on freckles.²⁷ None of them says a word about memory.

The five thousand years belong to a legend. The memory belongs to the twentieth century.¹²

By every hedge and wall

When the atomic bomb fell on Hiroshima in August 1945, ginkgo was among the burned trees that sprouted again from roots that had survived underground. One in Shukkeien garden, 1,400 metres from ground zero, was still standing in 1993, when the photographer Hiromi Tsuchida took its portrait.²⁶

The tree the lords of Kaifeng did not know has gone the way of Ouyang Xiu's grapes and pomegranates. People carried it around the world, and its leaves now gather in city streets far from the river country it came from.^{1, 4, 12}

He wrote down its beginning so that later ages would know. Nearly a thousand years on, they still can.