A dwarf shrub to about 3 ft high; stems square, glabrous. Leaves rather thin and membranous, 1⁄2 to 4⁄5 in. long, 1⁄/6 to 1⁄3 in. wide, narrowly elliptic-oblong to oblanceolate, rounded or notched at the apex, tapered or cuneate at the base. Flowers as in B. sempervirens, but with the rudimentary ovary of the staminate flowers much larger than in that species (as long as the inner sepals). An inhabitant of Japanese gardens; whether it is also found wild in its typical state is a matter on which Japanese botanists are not agreed. It is a pleasing little box, which resembles some of the small forms of B. sempervirens, but its stems and leaves are quite glabrous.
B. microphylla, although described from a garden plant, was the first to be named in a group of closely related wild boxes which are widely distributed in temperate E. Asia and usually considered as forming a single species of which B. microphylla must be regarded as the nomenclatural type. The following varieties are distinguished:
var. japonica (Muell.-Arg.) Rehd. & Wils. B. japonica Muell.-Arg. – A loose-habited shrub 3 to 6 ft high (more in the wild state); young stems glabrous, winged. Leaves 1⁄3 to 1 in. long, roundish obovate or inversely heart-shaped, sometimes as broad as long, tapered at the base, rounded or notched at the apex, smooth except for a slight down on the stalk when young. Native of Japan, and perhaps the least ornamental of boxes. It has an ungainly habit, and has not the healthy, vigorous aspect one associates with the genus. The roundish leaves, winged stems, and the absence of down are its distinguishing features. It also flowers more freely than any other species.
var. korean a Nakai – A dense shrub about 2 ft high; young stems and leaf-stalks downy. Leaves to about 3⁄5 in. long, obovate to elliptic-oblong, margins inrolled, venation scarcely visible on upper surface of leaves. Native of Korea and parts of China, valued in the north-eastern U.S.A. for its great hardiness.
var. riparia (Mak.) Mak. B. sempervirens var. riparia Mak. – Native of Japan, found on rocks by rivers in the mountains. Stems slender, often procumbent, leaves less than 1 in. long. This variety is said to be intermediate between var. japonica and the type.
var. sinica Rehd. & Wils. – -A shrub 3 to 18 ft high in the wild state; young stems downy. Leaves lustrous green, to 12⁄5 in. long, ovate to obovate, with the venation visible on the upper surface of the leaf. Native of China, where it is widespread. The “B. harlandii” of gardens belongs here; it is a dwarf form, perhaps of garden origin, growing to about 2 ft high, with leaves to 11⁄2 in. long and barely 1⁄4 in. wide.