Populus × berolinensis Dipp.

A supposed hybrid between P. laurifolia (female) and the Lombardy poplar, which arose in the Botanic Garden of Berlin some time before 1865. It is a handsome tree of slender columnar shape, with downy, slightly angled young shoots. Buds viscid, pointed. Leaves broadly ovate and rounded at the base, or somewhat diamond-shaped and wedge-shaped at the base, slender-pointed, finely toothed like those of P. laurifolia, and with a thin translucent border, 11⁄2 to 4 in. long, upper surface bright green, lower side pale, scarcely whitish, both sides soon glabrous; leaf-stalk downy at first, 3⁄4 to 11⁄2 in. long, not flattened.

The original tree was female. There is also a male form, originally distributed as P. certinensis, which is of unknown origin, but is believed to have originated in France.

P. × berolinensis is an uncommon tree in this country, but is widely planted in the prairie regions of N. America and the more continental parts of Europe, where it withstands the harsh winters and hot summers better than most poplars. In this country, the largest specimen grows in the poplar collection at Ryston in Norfolk; planted in 1914, it measures 85 × 81⁄2 ft (1969). A tree in the Forestry Commission collection at Alice Holt Lodge, nr Farnham, nineteen years planted, measures 52 ft × 2 ft 7 in. (1971).

P. × berolinensis is reported to occur occasionally in the wild where the two parent species are in contact.

The cross between P. nigra and P. laurifolia was made artificially by Schreiner and Stout, who raised 377 seedlings, of which three were named in 1934, namely, ‘Frye’, ‘Rumford’, and ‘Strathglass’. The first is growing well in the Forestry Commission collection at Alice Holt, where there is an example, pl. 1953, which measures 62 × 41⁄4 ft (1973). The other two are also in the collection.

Two hybrids raised in Russia around 1880 – ‘Petrowskyana’ and ‘Rasumowskyana’ – are closely allied to P. × berolinensis, and probably of the same parentage. The poplar that Dode named P. octorabdos is also near to P. × berolinensis.

P. × berolinensis and its allies are susceptible to Marssonina, a fungus that causes premature leaf-fall and seriously reduces the growth rate of these hybrids.

From the Supplement (Vol. V)

specimens: Forest Research Station, Alice Holt, Hants, Lawn, 56 × 31⁄2 (1979) and, Populetum, pl. 1955, 59 × 31⁄4 ft (1985); Prested Hall, Essex, three trees, the largest 108 × 103⁄4 ft (1977); Kingscliff Wood, Som., pl. 1951, 90 × 41⁄4 ft (1978); Queenswood, Heref., pl. 1961, 70 × 31⁄4 ft (1984).

The Schreiner and Stout hybrid ‘Frye’. pl. 1954, is now 85 × 61⁄2 ft at Alice Holt (1985).