花梣种

形态特征

花梣为中型落叶乔木，树高可达15–25米，主干直径约1米。树皮呈深灰色，即使老树仍保持光滑。

冬芽为淡粉棕色至灰棕色，表面密布灰色短绒毛。

叶片对生，羽状复叶，长20–30公分，具5至9枚小叶；小叶呈宽卵形，长5–10公分、宽2–4公分，叶缘具细锯齿与波状起伏，叶柄明显且长5–15毫米；秋季叶色会转变为黄色至紫红色。

花期在晚春新叶展开后，花朵密集组成圆锥花序（长10–20公分），每朵花具四片修长的乳白色花瓣（长5–6毫米），依靠昆虫授粉。

果实为细长翅果（长1.5-2.5公分），种子宽约2毫米，翅翼宽4–5毫米，成熟时由绿色转为褐色。

栽培与应用

花梣常被引种至原生区以北的欧洲地区作为景观树，其显著的花序特性使其成为观赏树种。部分栽培个体会嫁接于欧洲梣（Fraxinus excelsior）的砧木上，嫁接处常可见砧木树皮转为明显的纵裂纹理。

自树皮渗出的含糖汁液可提炼为甜味物质，中世纪晚期（约公元1400年）因其特性被比拟为《圣经》记载的吗哪，因而衍生出多种语言的俗名。现代化学中的甘露糖与甘露醇亦得名于此树汁。

Fraxinus ornus, the manna ash or South European flowering ash, is a species of Fraxinus native to Southern Europe and Southwestern Asia, from Spain and Italy north to Austria and the Czech Republic, and east through the Balkans, Turkey, and western Syria to Lebanon and Armenia.

Description

Fraxinus ornus is a medium-sized deciduous tree growing to 15–25 m (49–82 ft) tall with a trunk up to 1 m diameter. The bark is dark grey, remaining smooth even on old trees.

The buds are pale pinkish-brown to grey-brown, with a dense covering of short grey hairs.

The leaves are in opposite pairs, pinnate, 20–30 cm (7.9–12 in) long, with 5 to 9 leaflets; the leaflets are broad ovoid, 5–10 cm (2–4 in) long and 2–4 cm (0.8–2 in) broad, with a finely serrated and wavy margin, and short but distinct petiolules 5–15 mm (0.20–0.59 in) long; the autumn colour is variable, yellow to purplish.

The flowers are produced in dense panicles 10–20 cm (3.9–7.9 in) long after the new leaves appear in late spring, each flower with four slender creamy white petals 5–6 mm (0.20–0.24 in) long; they are pollinated by insects.

The fruit is a slender samara 1.5–2.5 cm (0.59–0.98 in) long, the seed 2 mm (0.08 in) broad and the wing 4–5 mm (0.2–0.2 in) broad, green ripening brown.

Cultivation and uses

Fraxinus ornus is frequently grown as an ornamental tree in Europe north of its native range for its decorative flowers—the species is also sometimes called "flowering ash". Some cultivated specimens are grafted on rootstocks of Fraxinus excelsior, with an often very conspicuous change in the bark at the graft line to the fissured bark of the rootstock species.

A sugary extract from the sap may be obtained from the bark of the tree; which was compared to biblical manna in late medieval times (attested circa 1400 AD), giving rise to the name of the tree in English, Spanish (fresno del maná), and Italian (frassino da manna). Likewise, the sugar alcohol mannitol derives its name from the extract.