A tree 100 ft high in the wild, but rarely more than half as high in this country, producing suckers freely; young shoots smooth, round; winter-buds thickly covered with a balsamic, very fragrant, viscid, yellowish resin, often 1 in. long, long-pointed. Leaves broadly ovate, rounded or slightly heart-shaped at the base, slender-pointed, very variable in size, round-toothed, ordinarily 2 to 5 in. long, 11⁄4 to 3 in. wide, dark shining green above, glabrous or slightly downy beneath, the pale or whitish ground conspicuously net-veined; stalk 2⁄3 to 2 in. long. Male catkins 3 in. long; female ones 4 or 5 in. long.
Native of N. America, where it is widely spread and abundant in the northern latitudes. It was introduced some time in the 17th century.
The balsam poplar was at one time represented in cultivation by a male clone, propagated by the suckers which it produced in great abundance. On vigorous suckers the leaves were occasionally of enormous size – up to 13 in. long and 10 in. wide. But this poplar was probably never very common; most of the plants grown under the name P. balsamifera were in fact P. candicans. The true P. balsamifera is a poor grower in this country – that is true both of the old clone and of subsequent importations. The great charm of P. balsamifera is the balsamic odour of the unfolding leaves in spring which fills the air around. But P. trichocarpa, its western ally, is just as fragrant and a more satisfactory tree in this country.
var. michauxii (Dode) Henry P. michauxii Dode; P. balsamifera var. subcordata Hylander – Leaves ovate, with a broad, rounded or subcordate base, slightly downy on the midrib and veins beneath; petioles and twigs also slightly hairy. This variety, which occurs wild in various localities in north-eastern N. America, has been confused with P. candicans, which is not known in the wild.
Dode, in describing this poplar (as a species), erroneously stated that it was the same as the poplar figured by the younger Michaux as P. balsamifera in Hist. Arb. For. Amer. Sept., Vol. III, t. 13, fig. 1; the poplar there figured is in fact typical P. balsamifera. But this misidentification is insufficient reason for invalidating the name P. michauxii, and still less for rejecting Henry’s var. michauxii, which is based on Dode’s ample description, drawn probably from a cultivated plant, and on leaf specimens from wild trees sent to him by Prof. Sargent.
P. × jackii Sarg. P. baileyana Henry – A natural hybrid between P. balsamifera and P. deltoides. Leaves glabrous, broad-ovate, up to 6 in. long and 5 in. wide, cordate at the base, long-acuminate at the apex, whitish beneath, and with quadrangular petioles, but showing the influence of P. deltoides clearly in the presence of two glands at the junction of the petiole with the blade, and the translucent margin with scattered hairs; the acuminate leaf-apex and the relatively wide leaves, also derive from P. deltoides. This hybrid was described in 1913 from specimens collected by J. G. Jack in Canada (Nun’s Island, at the mouth of the Chateauguay river and on the south bank of the St Lawrence at Beauharnois). The synonymous name P. baile ana is founded on the Jack specimens and also on one collected by L. H. Bailey near South Haven, Michigan, USA. The hybrid has since been found in numerous localities.
P. × jackii is of interest as a natural hybrid between a balsam and a black poplar, and could be regarded as the New World counterpart of P. × berolinensis, which has also been found in the wild.
P. balsamifera × P. trichocarpa – This cross between the eastern and western American balsam poplars occurs spontaneously in the wild, but the cultivated trees are mostly the result of deliberate hybridisation. The best known of these is ‘Tacatricho 32’ (‘TT 32’). It is a fast-growing female tree of remarkably narrow habit, much used in plantation for timber production, and also for shelter and screening. See further on p. 295.