In Bloom: Bamboo-leaf Oak

Bamboo-leaf oak at the Northwest corner of the Garden (Photo: Aleks Monk)

Bamboo-leaf oak is notable for its smooth, broad trunks that look remarkably like the legs of elephant.

Bamboo-leaf oak (Quercus myrsinifolia) is a wonderful broadleaf evergreen tree, but it’s easily missed by visitors to the Seattle Japanese Garden. Both specimens, planted in the 1960s, are over 40 feet tall and near the path, but they’re surrounded by other large trees in the northwest corner of the garden. It’s easy to walk under them without noticing their beauty and uniqueness.

Bamboo-leaf Oak is an oak tree, not a bamboo, but its slender evergreen leaves clustered at the ends of branches resemble the appearance of bamboo. Its smooth, broad trunks look remarkably like the legs of elephants. Other common names are Japanese live oak, Japanese white oak, and Chinese evergreen oak. In Japan, it’s known as shira kashi (shira means “white;” kashi means “oak”).

With time, Quercus myrsinifolia can reach 80 feet in height. Narrow when young, it matures with a compact-rounded crown. Its glossy, leathery leaves are narrow, lance-shaped and drooping, with finely-toothed margins and pointed tips. They’re 4 to 6 inches long, and are held alternately on the stem. The new leaves emerge rather late, in purple-bronze tones, and mature to a dark green on top, paler beneath. It has smooth, silvery-gray bark, and white wood.

Bamboo-leaf oak blooms in May, with two kinds of flowers. The male flowers are golden, resembling catkins, and hang downwards. The female flowers are upright, and appear in the upper part of the tree. Like other oaks, the fruit is an acorn, held in groups of 2 to 4, and are ½ to 1 inch in length. The acorn’s cap has 3-6 concentric rings. The species name, myrsinifolia, means “myrsine-leaves, from the Greek name for myrtle. A separate genus, Myrsine consists of numerous glossy-leafed evergreen trees and shrubs. Widely distributed in eastern Asia (including Korea, southern China, Laos, Thailand and Vietnam), Quercus myrsinifolia is native to central & southern Japan, usually in mixed evergreen forests. It’s planted as a shade tree in parks, and used as a tall hedge, in urban areas and in the countryside. When needed, its size is artfully controlled by the annual removal of branches & leaves throughout the tree. This pruning method is known as chirashi.

Bamboo-leaf oak has no serious pests or diseases, and is remarkably tolerant of heat, drought, varied soil conditions (sandy, clay & acid), and sun or part shade. It’s also the most cold-hardy of the Asian evergreen oaks, hardy to at least USDA Zone 7 (0-10 degrees F). Unlike the evergreen oaks of the Mediterranean and the Western U.S., it typically grows in high summer-rainfall areas. Its drought-tolerance is unusual – especially notable during periods of high temperatures.

It’s still rare in the United States, including Seattle, although older specimens are to be found in the Arboretum, at the Locks and in Redmond’s Marymoor Park. Its adaptability and cold hardiness are becoming known, and it’s now available in the U.S. from specialty nurseries.

Corinne Kennedy is a trained guide for Seattle Japanese Garden and a contributor to the garden's blog.