Plant of the Month

Plant of the Month: June 2024

Daimyo Oak

Quercus dentata Th.

= Quercus Daimio K. Koch

FAGACEÆ; Beech Family

A reader questioned the drawing of the leaf and acorn of this oak, that appears in my books Trees of Green Lake and North American Landscape Trees. So, here I show how this oak has variable leaves, including the kind illustrated in my books.

Quercus dentata is called in English Daimyo (Daimio) Oak, or (Japanese) Emperor Oak. In Japanese it is called Kashiwa. In Chinese it is called Hu Shu (柞栎). It is native in Mongolia, China, the S Kuriles, Korea, and Japan, and was introduced to Western cultivation in 1830. It was brought to North America by G.R. Hall in 1862. Extremely rare overall, it is sold these days mostly in its deeply lobed form called 'Pinnatifida'. Overall, the oak is remarkable for giant leaves, to 20 inches long and almost 12 inches wide, with bluntly rounded lobes (hence the name dentata) or deep undulations; downy beneath. Fall color tawny to russet, red rarely. Acorns squat, three-quarters on an inch, in distinctive shaggy-scaled cups. Growth usually slow, the crown often gaunt. The tree can reach 100 feet tall. One in in Japan with a trunk circumference of 17 feet 9 inches, may be over 600 years old. In 1937, the Arnold Arboretum sent the arboretum in Seattle acorns of this species.

Besides about 8 of the 1937 trees still in Washingtion Park Arboretum, others were planted elsewhere in Seattle, such as at Green Lake (the largest; now 93.75 feet tall, 103.5 feet wide, its trunk circumference 15 feet 2 inches), Woodland Park, and the Seattle Center. The deeply lobed cultivar exists in private gardens as relatively young, small trees.

My photos below show the leaf shape variations. In any form, I think this species handsome enough to warrant more planting. (In late August, the Green Lake giant had a break so severe that the entire tree was cut down.)

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