Obai - Obai

A deciduous shrub of the Oleaceae family (APG classification: Oleaceae). It grows to 1-2 meters tall, with green, 4-ridged, angular stems that grow long and slender in a slightly creeping manner, and root when the tip touches the ground. The leaves are compound with 3 leaflets, each of which is oblong, 1-3 cm long, dark green on the surface, and has short bristles on the edges. In March and April, before the leaves appear, yellow flowers bloom one by one in pairs. The flowers are 2-2.5 cm in diameter, open flat with six lobes at the top, and have a high-pitched shape with a long, tubular bottom, and are fragrance-free. There are two stamens that grow inside the flower tube. It is native to China, and the time when it was introduced to Japan is unclear, but it is listed as Obai in the Kadan Komoku (1681). It is easy to cultivate and is a sun-loving tree that grows well in any soil. It is cold-resistant and grows in Hokkaido. It is propagated by cuttings and layers. It is often planted in gardens, and is also used as a potted plant or bonsai, and is trained as a cliff. Its yellow flowers bloom in early spring, so it is called 'yellow plum' in reference to plum trees, and in China, it is called 'geishunka' (flowers welcoming the spring) because the blooming of these flowers marks the beginning of spring.

There are over 400 known species of the Juniperus genus in the world, but in Japan, in addition to Juniperus persica, other species include Juniperus humile, Juniperus japonica, and Juniperus japonica. Juniperus humile L. var. revolutum Stokes is an evergreen shrub native to the Himalayas, with odd-pinnate compound leaves that grow alternately, and yellow flowers bloom in corymbs at the ends of the branches in May and June. The upper part of the corolla is divided into five lobes that open flat, and the flowers have no fragrance. Juniperus mesnyi Hance ( J. primulinum Hemsl.) is an evergreen shrub native to Yunnan Province, China, with opposite trifoliate compound leaves, and yellow flowers with 6 to 10 lobes at the top of the corolla bloom in May. It is cold-resistant and is cultivated in areas south of the Kanto region.

[Yoshio Kobayashi July 16, 2021]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

モクセイ科（APG分類：モクセイ科）の落葉低木。高さ1～2メートルになり、茎は緑色で4稜(りょう)があって角張り、ややつる状に細長く伸びて、先が地につくと発根する。葉は3小葉からなる複葉で、小葉は長楕円(ちょうだえん)形、長さ1～3センチメートル、表面は深緑色で、縁(へり)に短剛毛がある。3～4月、葉の出る前に黄色の花が1個ずつ対生して開く。花は径2～2.5センチメートルで上部が6裂して平らに開き、下部が細長い筒になった高坏(たかつき)形で、香りがない。雄しべは2本で花筒の内側につく。中国原産で日本に渡来した年代ははっきりしないが、『花壇綱目(かだんこうもく)』（1681）には黄梅(おうばい)として出ている。栽培が容易で、土地を選ばずよく成長する陽樹である。耐寒性があり、北海道でも育つ。繁殖は挿木、取木による。庭園に植え、また鉢植えや盆栽によく用いられ、懸崖(けんがい)仕立てなどにする。早春に黄色の花が開くので梅になぞらえて黄梅といわれ、中国ではこの花が開くと春になるので迎春花(げいしゅんか)とよぶ。

　オウバイ属の植物は世界に約400種余りが知られているが、日本にはオウバイのほか、キソケイ、オウバイモドキ、ソケイなどが栽培される。キソケイJ. humile L. var. revolutum Stokesはヒマラヤ原産の常緑低木で、奇数羽状複葉の葉が互生し、5～6月ごろ、枝先の散房花序に黄色の花が開く。花冠の上部は5裂して平開し、花に香りがない。オウバイモドキJ. mesnyi Hance（J. primulinum Hemsl.）は中国雲南省原産の常緑低木で、3出複葉を対生し、5月に花冠の上部が6～10裂した黄色の花が開く。耐寒性があり関東地方以南で栽培される。

［小林義雄　2021年7月16日］

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