Rapidly growing trees; buds usually large, scaly and more or less resinous; leaves alternate, broad, toothed or sometimes lobed; flowers appearing before the leaves on large pendulous catkins; anthers red or purple.
In the following key mature leaves from trees are considered:
| Petioles round or channeled, scarcely or not at all flattened laterally. | |
| Leaves chalky-white tomentose beneath, some of them more or less lobed, blades 6-10 cm. long. | [1 P. alba.] |
| Leaves pubescent or whitish tomentose while young, never lobed, blades 10-17 cm. long | [2 P. heterophylla.] |
| Petioles strongly flattened laterally especially near the blade. | |
| Winter buds more than 8 mm. in length, stamens more than 20, capsules more than 3 mm. in diameter, leaves broadly deltoid, majority more than 8 cm. wide | [3 P. deltoides.] |
| Winter buds less than 8 mm. in length, stamens fewer than 20, capsules less than 3 mm. in diameter, leaves roundish ovate, majority less than 8 cm. wide. | |
| Winter buds more or less pubescent, dull; leaves generally with less than 12 teeth to a side | [4 P. grandidentata.] |
| Winter buds smooth or rarely somewhat pubescent, glossy; leaves with more than 12 teeth to a side | [5 P. tremuloides.] |
1. Populus álba Linnæus. Silver-leaf Poplar. [Plate 15.] Short-trunked trees with a round top, up to a meter or more in diameter; bark on young trees smooth, greenish-white or gray, becoming furrowed on old trees, gray or dark brown; shoots white tomentose, becoming smooth in age; leaves ovate or triangular, 3-5 lobed or irregularly toothed, hairy on both surfaces on expanding, becoming dark green and glabrous above, remaining white tomentose beneath; stamens about 8; wood light, soft and weak.
Distribution.—Introduced from Europe and escaped in all parts of the State.
Remarks.—This tree has long been under cultivation, and several horticultural forms have been introduced. It is falling into disuse on account of its habit of sending up root shoots. It adapts itself to all kinds of soil, grows rapidly, transplants easily, stands pruning well and has few insect or fungous enemies.
