Forestry

Tree and Shrub Identification

Populus Key

The genus now has many hybrid clones, most of which are not keyed out here.

Summer Key

1 Branchlets, outer bud scales, and lower surface of leaves permanently white tomentose; leaves usually lobed; petiole terete. Introduced. (white poplar) Populus alba
  Branchlets, bud scales, and leaves not white tomentose (when mature); leaves not lobed 2
2 (1) Petioles terete or grooved above; leaves becoming rusty along the lower surface of veins; buds very resinous and strongly balsamic fragrant 3
  Petioles flattened, especially near the base; leaves not rusty along the lower surface of veins 4
3 (2) Petioles and twigs pubescent; leaves heart shaped, pubescent beneath, especially on veins and midrib (Balm-of-Gilead poplar) Populus balsamifera var. subcordata
  Petioles, twigs and lower sides of leaves glabrous; leaves cuneate to rounded or subcordate at base, lanceolate to narrow ovate (balsam poplar) Populus balsamifera
4 (2) Leaves distinctly deltoid in shape, copiously dentate, bright or yellow green; buds not pubescent 5
  Leaves ovate to suborbicular or elliptic, not so strongly dentate, dull gray or gray-green 6
5 (4) Leaves broader than long, abruptly pointed at apex, with marginal teeth not conspicuously incurved; mature leaf blades on short branches (not sprouts) without basal glands; branches erect and more or less appressed to the main stem, forming a narrow, spirelike crown. Clone. Introduced. (Lombardy poplar) Populus nigra var. italica
  Leaves longer than broad, more or less taper pointed at apex, with marginal teeth rather conspicuously incurved; mature leaf blades with basal glands; branches spreading, forming a broad crown (eastern cottonwood) Populus deltoides
6 (4) Leaf margin finely dentate (20 or more teeth on a side); buds glossy brown (quaking aspen) Populus tremuloides
  Leaf margin coarsely dentate (with 5-15 coarse and remote unequal deltoid teeth); buds gray pubescent (bigtooth aspen) Populus grandidentata

 

Winter Key

1 Buds downy or silky 2
  Buds glabrous or resinous 3
2 (1) Buds and younger twigs both white downy (white poplar) Populus alba
  Buds pale downy; twigs glabrous or only slightly pubescent (bigtooth aspen) Populus grandidentata
3 (1) Twigs yellow, yellowish brown or olive green; buds not fragrant 4
  Twigs dark brown or reddish brown 5
4 (3) Lateral buds appressed, mostly under 8 mm long, crown very narrow (Lombardy poplar) Populus nigra var. italica
  Lateral buds divergent, usually 10 mm or longer; crown spreading (eastern cottonwood) Populus deltoides
5 (3) Buds small, less than 10 mm long, glossy, slightly resinous but not fragrant, margin of bud scales scarious (quaking aspen) Populus tremuloides
  Buds large, more than 15 mm long, resinous, fragrant 6
6 (5) Lateral buds with three visible scales; twigs hairy, at least at base (Balm-of-Gilead poplar) Populus balsamifera var. subcordata
  Lateral buds with two visible scales; twigs glabrous (balsam poplar) Populus balsamifera
Last Revised: Monday July 30 2007