A deciduous tree, not yet found by Europeans in a wild state, but from 30 to 65 ft high, as seen cultivated by the Chinese. It probably attains a larger size. Leaves alternate, ovate or oval, long and slender-pointed, toothed, 3 to 8 in. long, slightly hairy on both surfaces when young, becoming glabrous above. Flowers unisexual, the sexes on separate trees; they are inconspicuous, the males consisting of brown stamens only; female ones of a single pistil. Fruit flat and winged, one-seeded, rather like an enlarged fruit of wych-elm, oval-oblong, 11⁄2 in. long, tapering at the base to a short stalk; apex notched.
Introduced to France from China about 1896, and a few years later to Kew. It was first discovered in China by Henry as a cultivated tree, 20 to 30 ft high, but as its bark is and has for 2,000 years been highly valued by the Chinese for its real or supposed tonic and other medicinal virtues, it is never allowed to reach its full size, but is cut down and stripped of its bark.
The most interesting attribute of the tree is its containing rubber. The rubber is apparently of inferior quality, but the tree is of peculiar interest as the only one hardy in our climate that is known to produce this substance. If a leaf be gently torn in two, strings of rubber are visible. Fossils found in tertiary brown-coal deposits in Germany, and known as ‘Monkey’s Hair’, derive from the leaves of some extinct species of Eucommia; they are well enough preserved to burn when a match is put to them, giving off a smell of burning rubber.
At Kew, grown in good loam, it has proved absolutely hardy, and a vigorous grower. There is a good specimen to be seen by the Temple of Bellona, planted 1930 and measuring 42 × 43⁄4 ft (1967), and another fine specimen (see Plate 23) is in the Duke’s Garden. Two others of about the same size grow in the Cambridge Botanic Garden. It can be propagated by cuttings made of half-ripened wood put in gentle heat. Wilson introduced seeds to the Coombe Wood nursery, from which, no doubt, trees of both sexes have been raised, though female trees seem to be rare in gardens.