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Zelkova serrata
"Noma Keyaki", a 1,000-year old Keaki in Nose near Osaka in Japan, 25 m tall, 11.95 m trunk circumference; second-largest known specimen[1]
Scientific classification
Kingdom: Plantae Division: Magnoliophyta Class: Magnoliopsida Order: Rosales Family: Ulmaceae Genus: Zelkova Species: Z. serrata
Binomial name
Zelkova serrata (Thunb.) Makino

Zelkova serrata (Keyaki or Japanese Zelkova; Japanese: ケヤキ keyaki; Chinese: 榉树 ju shu) is a species of Zelkova native to Japan, Korea, eastern China, and Taiwan.^[2][3]

Foliage and flowers in spring

It is a medium-sized to large deciduous tree growing to 20-35 m tall, with a trunk up to 2 m (exceptionally 4 m) diameter with smooth grey bark, becoming flaky and browner on old trees. The branches are numerous, usually strongly ascending from a short trunk to give a high domed crown. The leaves are alternate, 3-11 cm long and 1.3-7 cm broad with a 2–7 mm petiole; hairless or finely hairy both above and below; the margin is sharply serrated with 8–16 teeth on each side. The autumn colour is orange to red. The flowers are 1.5 mm diameter, inconspicuous and yellowish-green with no petals, and are wind-pollinated. The fruit is a small nut-like dry drupe 2.5-3.5 mm diameter with a ridged surface.^[2][3]

There are two varieties, Zelkova serrata var. serrata in Japan and mainland eastern Asia, and Zelkova serrata var. tarokoensis (Hayata) Li on Taiwan; the latter differs from the type in its smaller leaves with less deeply cut serration on the margins.^[3]

The Japanese name, 木　means tree 挙げる means lift up hand, so a big tree that grows like a raised hand is the meaning of 欅.

It is often grown as an ornamental tree, both in its native area and in Europe and North America. The first cultivation outside of Asia was by Philipp Franz von Siebold, who introduced it to the Netherlands in 1830.^[3]

Numerous cultivars have been selected, including 'Fuiri Keaki' (variegated leaves), 'Goblin' (dwarf), 'Goshiki' (variegated leaves), 'Green Vase' (tall, narrow crown^[4]), 'Green Veil' (pendulous branchlets), 'Iruma Sango' (fastigiate), 'Nire Keaki' (semi-dwarf), 'Pulverulenta' (variegated leaves), 'Spring Grove' (upright crown), 'Variegata' (variegated leaves), 'Village Green' (fast-growing, straight trunk, vase-shaped crown^[5]), and 'Urban Ruby' (red autumn colour). It has also hybridised with Zelkova carpinifolia in Europe, the hybrid being named Zelkova × verschaffeltii.^[3]

Keaki wood is valued in Japan and used often for furniture, such as tansu.

The tree is a symbol of Saitama Prefecture.

Wikimedia Commons has media related to:

Zelkova serrata

Autumn colour, November, Saitama Prefecture, Japan.

Trees lining an avenue in Sendai, Japan

Tree at the Morton Arboretum (acc. no. 10-54-1)

A Japanese Sendai-dansu for kimono made from keaki wood