Quercus serrata - Quercus serrata

A deciduous tall tree of the Fagaceae family (APG classification: Fagaceae). It grows to a height of around 15 meters, with larger ones reaching over 25 meters and a diameter at breast height of 80 centimeters. The bark is grey-brown and irregularly shallowly lobed vertically. In older trees, it turns grey-white and deeply lobed. The taproot is vertical and deep, reaching up to 3 meters below ground, and even in young seedlings the taproot is thick and rod-shaped. The branches grow obliquely upwards, with thin branches at the tips. One-year-old branches are grey-brown and hairy, but later become hairless. The lenticels are white and scattered, and the winter buds are conical with five ridges and densely covered with brown scales. The leaves are alternate, with petioles 3-20 mm long, gray-green with soft hairs on the underside, obovate or oblong leaf blades 6-15 cm long, and leaf margins with coarse, slightly inward-curving serrations. There are 9-12 pairs of lateral veins. The male inflorescences hang down from the lower part of the new shoots immediately after the leaves open, are 4-8 cm long, and produce many flowers. They are wind-pollinated flowers that release countless pollen from 4-6 stamens. The female inflorescences grow obliquely upward from the axils at the top of the new shoots, are 1-2 cm long, and contain two or several flowers enclosed in an involucre, with a heart-shaped stigma divided into three lobes. In autumn, the ovary develops into a nut, and the involucre grows by affixing together like a tile layer, forming a cupule. The nuts are cylindrical and elliptical, brown, with the stigma remaining at the top, and one-third to one-quarter of the lower part being enclosed in the cupule. The nuts do not have dormancy, and within a month of falling, they produce roots about 20 cm long, but the cotyledons remain inside the seed and survive the winter as underground cotyledons. They are extremely sensitive to dryness.

It is a sun-loving tree and young trees grow quickly. It has strong sprouting power and can reach a height of 15 meters 20 years after felling, forming one of Japan's leading firewood and charcoal forests along with the Sawtooth Oak. It is most commonly found in the low mountain areas throughout Japan north of Tanegashima and on the Korean Peninsula, but natural forests are rare. Some forests are still managed artificially to use fallen leaves for plowing into fields for tobacco cultivation or as logs for shiitake mushrooms, but forests that have been left abandoned due to the recent fuel revolution are turning into forests of oaks that are more shade-tolerant, just like pine forests. The wood is ring-porous and has beautiful grain. Contrary to conifers, the faster it grows, the higher its specific gravity and the better the quality of the wood, but because large diameter trees are no longer available, most oak wood for furniture and other purposes is made from Mizunara, a higher quality variety from Hokkaido.

The foreign words oak (English), chêne (French), and Eiche (German) refer to the genus Quercus , which includes Quercus serrata, but in the narrow sense, they refer to oaks in the subgenus Lepidobalanus, which are evergreen and contrast with oaks with ring-like patterns on the cupule, and which have the characteristic of having overlapping scales on the cupule. This oak is a large group that is widely distributed in the temperate zone of the Northern Hemisphere, mainly in North America, and includes more than 200 species. European oaks Q. robur and Q. petraea grow to large trees and are revered as the "kings of the forest." They are used for building materials, furniture, and barrels for Western wine, and their large amounts of nuts are important as pig feed along with beech. There are evergreen oaks on the Mediterranean coast, in the warm temperate zone, and in the subtropics, and they are sometimes distinguished as holm oak and live oak. Simply oak refers to deciduous oaks, so it is not accurate to translate it as oak. In China, the character "" is used to distinguish it from the "" of oak. The Japanese name "nara" usually refers simply to konara, or sometimes to mizunara. Hahaso (柞) is an old name for konara and sawtooth oak.

[Shinsuke Hagiwara January 21, 2020]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

ブナ科（APG分類：ブナ科）の落葉高木。高さ15メートル前後で、大きいものは25メートル以上、胸高直径80センチメートルに達する。樹皮は灰黒褐色で縦に不規則に浅裂する。老樹では灰白色となり深裂する。主根は垂直、深根型で、地下3メートルに達し、稚苗も主根は太く棒状となる。枝は斜上し、先端は細く分枝する。1年枝は灰褐色で有毛であるが、のちに無毛となる。皮目は白色で散生し、冬芽は5稜(りょう)のある円錐(えんすい)形で、褐色の鱗片(りんぺん)で密に包まれる。葉は互生し、葉柄は3～20ミリメートル、裏面は軟毛が残り灰緑色、葉身は倒卵形ないし長楕円(ちょうだえん)形をなし、長さ6～15センチメートル、葉縁にはやや内曲する粗い鋸歯(きょし)がある。側脈は9～12対。雄花序は開葉直後に新枝の下部に数個下垂し、長さ4～8センチメートル、花は多数。4～6個の雄しべから無数の花粉を放出する風媒花である。雌花序は新枝の上部の葉腋(ようえき)から斜上し、長さ1～2センチメートルで、花は総包に包まれて2個ないし数個つき、柱頭は心臓形に3裂する。秋には子房が発達して堅果となり、総包は瓦(かわら)重ね状に癒着しながら成長し殻斗(かくと)となる。堅果は円柱状楕円形で褐色、上端に柱頭が残存し、下部は殻斗に3分の1ないし4分の1が包まれる。堅果に休眠性がなく、落下して1か月足らずで長さ20センチメートルほどの根を出すが、子葉は種子内にとどまり、地下子葉として冬を越す。乾燥には極端に弱い。

　陽樹で若木の成長は早い。萌芽(ほうが)力が強く、伐採後20年で樹高15メートルに達し、薪炭林(しんたんりん)としてクヌギとともに日本を代表する雑木林をつくる。種子島(たねがしま)以北の日本全土および朝鮮半島の低山帯にもっとも普通にみられるが、天然林はまれである。タバコの栽培では落ち葉を畑にすき込んだり、シイタケの原木として利用するために、人為的に管理された林も残るが、近年の燃料革命で放置された林は、マツ林と同様に、より耐陰性の強いカシ類の林に変わりつつある。材は環孔材で木目は美しい。針葉樹とは逆に、成長の早いものほど比重は重く良材となるが、大径木がなくなったため、家具などのナラ材はほとんどがより良質の北海道産のミズナラを用いる。

　外国語のoak（英語）、chêne（フランス語）、Eiche（ドイツ語）はコナラを含むナラ属Quercusをさすが、狭義には、常緑で殻斗に輪紋様があるカシ類と対比されるコナラ亜属Lepidobalanusに含まれ、殻斗に鱗片が瓦重ね状につく特徴があるものをさす。このナラ類は北アメリカを中心に北半球の温帯に広く分布し、200種以上を含む大きなグループである。ヨーロッパナラQ. robur、Q. petraeaは大木となり、「森の王者」と尊ばれ、建築材、家具材、洋酒の樽(たる)材として、また大量の実はブナとともにブタの飼料としてたいせつであった。地中海沿岸や暖帯、亜熱帯には常緑のナラもあり、holm oak、live oakとして区別することもある。単なるoakは落葉性のナラをさし、カシと訳すのは正確ではない。中国では「」の字をあて、カシの「」と区別する。和名のナラは、単にコナラ、ときにミズナラをさすのが普通である。ハハソ（柞）はコナラやクヌギの古名である。

［萩原信介　2020年1月21日］

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