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A tree up to 80 ft high in cultivation; young stems angled and hairy at first, becoming terete and glabrous, brownish green the first season, greyish the second; lateral buds slightly viscid, slender, loosely appressed. Leaves on strong shoots ovate or elongate-ovate, 71⁄2 to 12 in. long, 5 to 8 in. wide, acute at the apex, mostly strongly cordate at the base, petioles stout, up to 3 in. long, reddish; leaves on young spurs 3 to 41⁄4 in. long, 17⁄8 to 21⁄2 in. wide, ovate to narrow-ovate, acuminate at the apex, rounded or slightly cordate at the base, petioles 11⁄4 to 21⁄2 in. long, slender; leaves at the ends of old spurs resembling those of the long shoots but not quite so large; all leaves dark green above, undersides pale green, becoming whitish on dried specimens, midrib and main veins densely furnished with more or less persistent curled hairs which near the base of the blade extend onto the minor veins, margins crenate-serrate to serrate, petioles hairy at first like the midrib, becoming glabrous. Catkins not seen.
The above description is made from specimens taken from a tree at Westonbirt, Glos., grown as P. szechuanica var. tibetica, and from another at Stourhead, Wilts. The origin of these trees, which are very similar, is not known, but they agree well with material in the Kew Herbarium taken from young trees received from the Arnold Arboretum in 1916 under Wilson’s number 4361; the corresponding herbarium specimen was collected by him in W. Szechwan near Mupin in 1910, and plants were sent under the same number. The description of P. szechuanica in previous editions of this work was based on the Kew plants, which no longer exist, and the hairiness of the shoots and leaves was remarked on. The Kew plants, and probably those at Westonbirt and Stourhead, came from the Arnold Arboretum under the name P. szechuanica, in which W.4361 had been included by Schneider. In 1933 Rehder described P. cathayana and transferred W.4361 to this new species. But the cultivated material under W.4361 in the Kew Herbarium agrees better with P. szechuanica, and that is certainly true of the Westonbirt and Stourhead trees. Probably all represent a pubescent form of that species. Wilson’s 4257, collected during the Veitch expedition, appears to be the same; also a specimen collected by Forrest in Yunnan on the Mekong-Salween divide.
The measurements of the trees referred to above are: Westonbirt, 82 × 41⁄4 ft (1972); Stourhead, 82 × 5 ft (1965) and 80 × 7 ft (1970).
Whatever may be the identity of the plants received under Wilson’s 4361, the undoubtedly true P. szechuanica was introduced by means of young plants collected south-east of Kangding (Tatsien-lu) in western Szechwan (W.4355). A tree under this number at Borde Hill in Sussex died around 1960 but was propagated by Messrs Hillier and is the source of the plants they distributed. The same firm’s P. szechuanica var. tibetica derived from stock received from a French nurseryman, and its history is unknown.
Roy Lancaster tells us that he saw what seemed to be P. szechuanica growing in the area of Minya Konka. This is not far from the locality where Wilson collected his plants.
The Stourhead tree mentioned on page 323 has been felled.
This variety is founded on specimens of uncertain attribution collected in the N.W. Himalaya by Thomson and by Schlagintweit. Schneider considered that they represented a pubescent form of P. szechuanica and under this variety he also placed Wilson’s 4527, collected in Szechwan. If Schneider is right, the Westonbirt and Stourhead trees would be referable to var. tibetica, but further investigation may show that the balsam poplar of the N.W. Himalaya is specifically distinct from P. szechuanica.