Ginkgo - Ginkgo

Japanese: イチョウ - いちょう

It is a large deciduous tree of the Ginkgo family (classification based on molecular phylogeny: Ginkgoaceae), and the larger ones can reach a height of 45 meters and a diameter of 5 meters. The bark is gray and thick, with vertical cracks. Aerial roots called milk may hang down from the trunk branches. There are long and short branches, and the leaves are sparsely alternate on the long branches, while on the short branches several leaves grow in dense bundles. The leaf blade is fan-shaped with a single notch in the center, and some have more irregular notches. The leaves turn a beautiful yellow in autumn. Dioecious. The male flowers are short pale yellow spikes with many stamens. The female flowers are green, and two ovules are attached to the end of the stalk. The pollen of the male flowers is scattered far away by the wind. The pollen that enters the pollen chamber of the ovule in April develops there, and before maturation in early September, sperm are produced, which enter the archegonia and are fertilized. The production of sperm was discovered in 1896 (Meiji 29) by Ikeno Seiichiro and Hirase Sakugoro, and its taxonomic position was clarified. The original tree on which the sperm was discovered is still on display in the Koishikawa Botanical Gardens of the University of Tokyo. The seeds are drupe-like, and when ripe the outer seed coat turns yellow and is fleshy with a foul odor, while the inner seed coat is hard and white with two or three ridges. The plant blooms in April and the seeds ripen in October. Native to China, it is cold- and heat-tolerant and is widely planted from Hokkaido to Okinawa, as well as in other parts of the world.

It is strong and resistant, and grows in any soil. It grows quickly and is rarely affected by diseases and insects. It has strong sprouting power and can withstand heavy pruning. Its bark is thick, corky, and has air pockets, making it highly fire-resistant, and it has long been known as a fire-resistant tree. There are varieties such as the Ohatsuki ginkgo, which has deformed seeds on the edge of the leaves, the Trumpet ginkgo, which has trumpet-shaped leaves, and the Variegated ginkgo, which has white and yellow spots on the leaves. It is usually propagated by seed, but it can also be propagated by cuttings and grafts. The wood is pale yellow, soft, dense, and glossy, with little recurving, cracking, or shrinking, and is used in architecture, tools, sculptures, etc. The seeds are called ginkgo nuts and are edible. The trees are widely used as garden trees, park trees, street trees, windbreaks, firebreaks, and bonsai, and in recent years they have also been cultivated as fruit trees for producing seeds.

[Yayoi Hayashi March 19, 2018]

Folklore

Ginkgo trees are often found at shrines and temples, but it is taboo to plant them in private homes, and this is true throughout the country. There are many legends about ginkgo trees, including the "Cane Ginkgo" tree, which is said to have grown from the walking stick of a high priest such as Kobo Daishi, which was stuck in the ground and grew branches and leaves. One example is the one at Zenpukuji Temple in Azabu, Tokyo. The name "upside-down ginkgo" comes from the fact that the branches and leaves grow facing downwards, but there are old ginkgo trees all over the country, such as at Yogoji Temple in Kawasaki City, Kanagawa Prefecture, which are said to improve milk production if you scrape off the aerial roots that grow on old ginkgo trees and drink the decoction. In addition, there is a ginkgo tree in the grounds of Kishimojin Shrine in Zoshigaya, Tokyo, which is said to be a "child-giving ginkgo" tree, and if a woman holds the tree and puts the leaves or bark on her skin, she will be blessed with a child. There is also a tree called "crying ginkgo," and there are various stories about its origin. The famous one at Mamasan Kohoji Temple in Ichikawa City, Chiba Prefecture, is said to come from the fact that the monk Nitcho Shonin (1252-1317) chanted sutras around the tree while crying after he was disowned by his father.

[Tokihiko Oto, March 19, 2018]

[References] | Seiichiro Ikeno | Koishikawa Botanical Garden | Sakugoro Hirase

Yellow leaves of ginkgo
It is often used as a roadside tree or park tree, and its leaves turn a beautiful yellow in autumn. ©Shogakukan Photo by Hideyuki Asakura ">

Yellow leaves of ginkgo

Ginkgo male flower
It blooms around April. It has many stamens and scatters a large amount of pollen on the wind. ©Shogakukan Photo by Okuyama Hisashi ">

Ginkgo male flower

Ginkgo female flower
The tip of the long fruit stalk is divided into two, each of which bears one ovule. ©Shogakukan Photo by Okuyama Hisashi ">

Ginkgo female flower

Ginkgo fruit
It ripens on female trees from mid to late October. The seeds are drupe-like, and when ripe, the outer seed coat turns yellow, and they are fleshy and have a foul odor. The seeds are called ginkgo nuts and are edible. ©Shogakukan Photo by Hideyuki Asakura ">

Ginkgo fruit

Ginkgo (tree shape)
©Junzo Fujishima ">

Ginkgo (tree shape)

Ginkgo
©Shogakukan ">

Ginkgo

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

Japanese:

イチョウ科（分子系統に基づく分類：イチョウ科）の落葉大高木で、大きいものは高さ45メートル、直径5メートルに達する。樹皮は灰色で厚く、縦に割れ目ができる。幹枝から乳といわれる気根を下垂することがある。枝には長枝と短枝があり、葉は長枝ではまばらに互生し、短枝では数枚が密に束生する。葉身は扇状で中央に一つの切れ込みがあり、それ以上に不規則に切れ込むものがある。秋には美しく黄葉する。雌雄異株。雄花は淡黄色の短い穂となり、多数の雄しべがある。雌花は緑色で、果柄の先に2個の胚珠(はいしゅ)がつく。雄花の花粉は風によって遠方まで飛散する。4月に胚珠の花粉室に入った花粉はそこで発育し、9月上旬の成熟前に精子を生じ、造卵器に入り受精する。精子のできることは、1896年（明治29）池野成一郎、平瀬作五郎によって発見され、分類学上の位置がはっきりした。この精子が発見された原木は、現在も東京大学小石川植物園内に健在している。種子は核果様で、熟すと外種皮は黄色となり肉質で悪臭があり、内種皮は硬く白色で、2～3の稜線(りょうせん)がある。4月に開花し10月に種子は成熟する。中国原産で、耐寒耐暑性があり、北海道から沖縄まで広く植栽され、また世界各地に植えられている。

　強健で抵抗力が強く、土地を選ばず生育する。成長は早く、病虫害は少ない。萌芽(ほうが)力が盛んで、強い剪定(せんてい)にも耐える。樹皮は厚く、コルク質で気胞分があり耐火力に優れ、古くから防火樹として知られる。葉の縁(へり)に奇形的に種子をつけるオハツキイチョウ、葉がらっぱ形をなすラッパイチョウ、葉に白や黄の斑(ふ)のあるフイリイチョウなどの品種がある。繁殖は普通は実生(みしょう)であるが、挿木や接木もできる。材は淡黄色をなし、柔らかく緻密(ちみつ)で光沢美があり、反曲折裂および収縮が少なく、建築、器具、彫刻などに利用する。種子は銀杏(ぎんなん)といい食用とする。木は庭園樹、公園樹、街路樹、防風樹、防火樹、盆栽など広く利用され、近年は種子をとる果樹としても栽培される。

［林　弥栄　2018年3月19日］

民俗

神社や寺院などに多くみられるイチョウは、民家に植えるのを忌み嫌うが、これは全国的である。イチョウについては多くの伝説が語られており、杖(つえ)銀杏というのは、弘法(こうぼう)大師などの高僧が携えた杖を地面にさしたのが成長して枝葉を生じたといわれ、東京・麻布(あざぶ)の善福寺にあるものなどはその一例である。また、逆さ銀杏というのは枝葉が下を向いて生えるのでいったが、イチョウの古木に生じる気根を削って煎(せん)じたものを飲むと乳の出がよくなるという乳銀杏の古木が、神奈川県川崎市の影向寺(ようごうじ)など全国各地にある。このほか子授け銀杏といって、東京・雑司ヶ谷(ぞうしがや)の鬼子母神(きしもじん)の境内にあるイチョウは、その木を女が抱き、葉または樹皮を肌につけていると子供が授かるという。泣き銀杏というのもあるが、そのいわれはさまざまで、有名な千葉県市川市の真間山(ままさん)弘法寺(ぐほうじ)のものは、日頂上人(にっちょうしょうにん)（1252―1317）が父の勘当を受けたためにこの木の周りを泣きながら読経したからという。

［大藤時彦　2018年3月19日］

[参照項目] | 池野成一郎 | 小石川植物園 | 平瀬作五郎

イチョウの黄葉
街路樹、公園樹などに多く利用され、秋には美しく黄葉する©Shogakukan　撮影／朝倉秀之">

イチョウの黄葉

イチョウの雄花

イチョウの雌花

イチョウの果実

イチョウ〔樹形〕

ぎんなん

出典　小学館　日本大百科全書(ニッポニカ)日本大百科全書(ニッポニカ)について　情報 | 凡例

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