A tree 80 to 90 ft high; young shoots glabrous or minutely downy; winter buds resinous. Leaves composed of sometimes five, usually seven, leaflets, which are narrow-oblong or obovate, 5 to 8 in. long, about one-third as much wide, tapering to a fine point, shallowly and evenly toothed, the stalk 1⁄/6 to 5⁄8 in. long. Panicle 8 to 14 in. long, and 2 to 4 in. wide at the base, narrowing gradually to the top, the basal one-fifth naked. Flowers on glabrous stalks, white, 1⁄2 to 3⁄4 in. across; petals four; stamens rather longer than the petals. Fruit truncate or slightly indented at the top, subglobose, 2 in. in diameter, rough, but not spiny.
Native of N. China, and although known to botanists for over seventy years was only introduced in 1912. It was collected near Pekin by Purdom, and from seeds sent by him to the Arnold Arboretum plants were raised and distributed. The tallest of these at Kew is now 33 × 13⁄4 ft (1966) and no longer suffers from late spring frosts, as it did when young. For many years A. turbinata was grown on the continent as A. chinensis, and even figured under that name, but the true plant is absolutely different.
A. wilsonii Rehd. – This tree was introduced by Wilson from Szechwan and Hupeh, China, in 1908. It was first considered to be A. chinensis, to which indeed it is very closely allied. It may be distinguished from A. chinensis as follows: Leaflets longer stalked, not generally so tapered at the base, but rounded or even slightly heart-shaped there; more downy at first beneath (but in both species becoming glabrous); veins more numerous (up to twenty-two pairs), forming at their junction with the midrib a more obtuse angle than in A. chinensis. Flower-stalks more downy. Fruit ovoid to pear-shaped, with a mucro at the apex, and, according to Rehder, with the husk only half as thick as in A. chinensis. Seed larger, with the scar (hilum) covering about one-third (one-half in A. chinensis). A. wilsonii has a more southern distribution. Racemes up to 16 in. long.
It flowered at Caerhays in June 1934. The tree there, raised from W. 200, is 48 ft high, with 48 ft diameter of spread (1966).
These two chestnuts, with A. indica, belong to a distinct section of the genus (Calothyrsus), but A. indica has broader panicles with less crowded, more erect branches, larger flowers, and broader petals.
From the Supplement (Vol. V)
The tree at Kew remains the same height as when measured in 1972 (34 ft) and is 21⁄2 ft in girth (1981). It was planted in 1913. Other examples, almost certainly of the same date and provenance, are: Myddelton House, Enfield, Middx., 20 × 21⁄2 ft (1976); Aldenham House, Herts., 36 × 21⁄2 ft (1976).
On a visit to China in 1979, Roy Lancaster saw two trees by the West Lake, Hangchow, in Chekiang province, the larger 60-70 ft high and 6 ft in girth at breast-height. They were in flower, 'the slender tapering cylindrical panicles, up to 16 in. long, leaning out or gently ascending from the shoot tips. The white petals were exceeded by the stamens, and the overall effect of some hundreds of inflorescences was staggering' (The Garden (Journ. R.H.S.), Vol. 105 (1980), p. 122, with colour photograph). As Mr Lancaster suggests, this species must need a continental climate to thrive.
A. wilsonii – The tree at Caerhays, Cornwall, now measures 62 × 71⁄2 + 51⁄4 ft (1984); another example, at Melbury, Dorset, in the Pleasure gardens, is 70 × 51⁄2 ft (1980).