832 Yearbook^ of Agriculture 1949 



K. Deciduous leaves borne singly (alternate), not divided into leaflets (simple), leaf 

 edges lobed, Nos. 45 to 50 (see also No. 35). 



45. WHITE POPLAR, Populus alba L. (ebele; silver poplar and Bolleana poplar are 

 clones). Large, much branched tree. Bark smooth, whitish or light gray. Leaves long- 

 stalked, oval or 3- or 5-lobed and maplelike, 2 1 /; to 4 inches long, short-pointed, coarsely 

 and irregularly toothed, dark green above with a white hairy coat beneath. Male and 

 female flowers on different trees in early spring, many in clusters 2 to 3 inches long. 

 Capsules with cottony seeds. Native from central and southern Europe to central Asia. 

 Planted across the United States and naturalized in Eastern States and adjacent Canada. 

 Spreads by objectionable root-sprouts. The commonly cultivated silver poplar, a clone 

 with maplelike leaves silvery white beneath, is tolerant of city smoke but its leaves 

 become dirty colored from city dust. Bolleana poplar is another clone with columnar 

 shape and leaves green beneath. Gray poplar (P. canescens (Ait.) Sm. ), thought to be 

 a hybrid of white poplar and European aspen (P. tremula L.), has the leaves toothed but 

 not lobed. Zone 3. 



46. EUROPEAN WHITE BIRCH, Betula pendula Roth (European birch, European weeping 

 birch; B. alba L. in part). Medium-sized tree with slender, drooping branches. Bark 

 white, papery. Leaves long-stalked, triangular, 1 to 2 l /z inches long, long-pointed, doubly 

 toothed, also deeply lobed in the commonly cultivated varieties, smooth. Flowers male and 

 female, small, in narrow clusters in early spring. Fruiting cones 1 inch long, narrow, 

 slender-stalked. There are numerous horticultural varieties. Extensively planted across the 

 United States as a lawn tree for its white bark and graceful drooping branches. Subject 

 to attacks by the bronze birch borer. Zone 2. 



47. WHITE MULBERRY, Morus alba L. (silkworm mulberry; Russian mulberry and 

 weeping mulberry are varieties ) . Small tree with rounded crown and spreading branches ; 

 juice milky. Leaves broadly oval but variable in shape, 2/4 to 7 inches long, rounded or 

 heart-shaped at base, short-pointed, coarsely toothed and often lobed, light green and 

 smooth above, slightly hairy beneath. Male and female flowers small and greenish, 

 clustered, in spring. Fruits tys to 1 inch long, white, pinkish, or purplish, edible. Native of 

 China. Extensively grown and naturalized in many countries, as the leaves are the main 

 food of silkworms. Widely planted for ornament across the United States and naturalized 

 in the East. Russian mulberry, a hardy variety, has been vised in shelterbelts. Male trees 

 or fruitless varieties, such as the rapidly growing Kingan fruitless variety, are preferred. 

 Zone (4). 



48. LONDON PLANETREE, XPlatanus acerifolia (Ait.) Willd. (P. occidentalisX 

 orient alis ). Large tree with upright axis, spreading branches, and rounded crown. Bark 

 peeling off in large flakes, smoothish, with patches of brown, green, and gray. Leaves 

 long-stalked, heart-shaped, 5 to 10 inches long and wide, 3- or 5-lobed, with edges of the 

 triangular pointed lobes smooth or with few teeth, bright green and shiny above, pale 

 beneath. Flowers male and female in ball-like clusters in spring. Fruit of usually 2 bristly 

 balls 1 inch in diameter, conspicuous on trees in winter. Probably a hybrid between Ameri- 

 can sycamore and Oriental planetree, originated long ago. Widely planted as a street tree 

 in eastern United States and Pacific coast and southern Rocky Mountain regions. Tolerant 

 of city smoke and alkali but subject to a canker disease. Zone 5. 



49. CHINESE PARASOLTREE, Firmiana platanifolia (L. f.) Schott & Endl. (Phoenix-tree, 

 Japanese varnish-tree, bottletree; Firmiana simplex auth., Sterculia platanifolia L.). 

 Small to medium-sized tree with rounded crown. Bark smooth, gray green. Leaves long- 

 stalked, very large, heart-shaped, 6 to 12 inches long, 3- or 5-lobed with pointed lobes 

 and smooth edges, finely hairy beneath. Flowers small, yellow green, l /z inch long, in 

 clusters 8 to 18 inches long in summer. Fruit 2 to 4 inches long, showy, of 4 or 5 podlike 

 parts with pealike seeds. Native of China and Japan but widely planted as an ornamental 

 and street tree in warmer regions of United States, including South Atlantic and Gulf 

 States and California. Naturalized in Southeastern States. Zone 7. 



50. ENGLISH OAK, Quercus robur L. Medium-sized to large spreading tree with short 

 stout trunk, widespreading branches, and broad rounded crown. Bark dark, deeply 

 furrowed. Leaves oblong, 2 to 5 inches long, with 7 to 15 rounded lobes, smooth, dark 

 green above and pale blue green beneath. Flowers male and female, small, in early spring. 

 Acorns 1 to 5 on a stalk 1 to 3 inches long, % to 1 inch long, a third enclosed by the cup. 

 There are many horticultural varieties. Native of Europe, northern Africa, and western 

 Asia. In the United States planted chiefly in the Pacific, Gulf, and South Atlantic States. 

 Zone 4. 



ELBERT L. LITTLE, JR._, is dendrologist in the Division of Dendrology and 

 Range Forage Investigations, Forest Service, Washington, D. C. 



