Populus deltoides Marsh. subsp. deltoides, southern cottonwood, eastern cottonwood. Tree, winter–deciduous, not clonal, with 1—3 thick trunks, in range < 38 m tall; dioecious; shoots with long–petiolate leaves, having resinous, lanceoloid–ovoid winter buds, somewhat aromatic, glabrous or sparsely short–pilose; bark initially tight, dull tannish gray, on trunk thick and difficult to remove, coarsely and deeply fissured on trunk and major branches, light brown.
Stems initially ridged becoming cylindric, with transverse leaf scars, leaf scars narrowly crescent–shaped; young twigs somewhat knobby with leaf bases and sets of terminal bud scars, gray and brownish green; pith 5–angled and spongy whitish.
Leaves helically alternate, simple, petiolate, with stipules; stipules 2, attached at base of petiole and node junction extending across node, triangular–linear to strap–shaped, 8—18 × 1.2—2 mm, ± green, long–tapered base–to–tip, with wavelike teeth on margins, glutinous, early–deciduous, initially fleshy drying flat, with straight hairs to 0.2 mm long; petiole cylindric above base to compressed side–to–side to flattened above midpoint, 50—70 mm long, initially short–pilose, at top with 3(—6) light green, short–stalked, obovoid, fingerlike, or paddlelike glands 0.4—1.4 mm long; blade truncate to subcordate at base, serrate and puberulent–ciliate on margins, having (6—)12—20(—30) per margin and inrolled during early development, short–acuminate at tip, pinnately veined with principal veins raised on lower surface, upper surface puberulent, lower surface when developing exposed surface puberulent to short–pilose aging glabrescent, hidden portion glabrous.
Inflorescences unisexual catkins, racemelike, emerging before leaves from base of winter buds on stiff stems, many–flowered, flowers alternate, bracteate, glabrous.
Staminate inflorescence catkin (ament) lax and pendent, lanceoloid–cylindric, initially 50—70 mm long increasing 2× during pollen discharge and flowers maturing from the top of inflorescence to the base, when fully expanded to 140 × 13—15 mm; peduncle short, to 5 mm long; rachis often arching downward at base and ± straight to tip, cylindric or inconspicuously ridged on lower aments, smooth, pale green base–to–tip; bract (bractlet) subtending floral axis (“pedicel”) 0.5—1 mm with persistent base; floral axis 1—2 mm long at first dehiscence of anthers increasing 2—3×; involucre appearing like a perianth, broad and spreading, ± platelike (not funnel–shaped) aging with edges somewhat turned downward, 2.5—2.8 mm across, light green, glabrous.
Staminate flower = stamens attached to involucre, 4.5—9 mm across; perianth absent; stamens ca. 60, attached to and scattered on inner surface of involucre, exserted and hanging over involucre rim; filaments threadlike, mostly 1—1.4 mm long, white; anthers basifixed, dithecal, 0.9—1.4 mm long, yellow or purple–red, longitudinally dehiscent; pollen pale yellow; pistil absent.
Pistillate inflorescence catkin lax and nodding, with developing fruits 80—145 mm long, 25—40–flowered, glabrous; peduncle at anthesis < 5 mm long not increasing in fruit, with bud scars at base; rachis ± smooth and not ridged but with bases of bracts raised (cushions), each base with a crescent–shaped scar of bracts; bract (bractlet) subtending floral axis and somewhat cupped over flower bud, scooplike, 4—5 mm long including long fringes on margins above midpoint and at tip, white and cream–colored aging reddish to brown and scarious, abscising around anthesis at base cushion on floral axis; floral axis (pedicel) at anthesis to 3.5 mm long ascending and increasing 2× in fruit, green, expanding as base of “involucre”; involucre funnel–shaped, ca. 2 mm long, green but paler and thinner on uneven rim, aging scarious and appressed to fruit base.
Pistillate flower = pistil (surrounded by involucre), 4—5 mm across (= ascending stigmas; perianth absent; stamens absent; pistil 1; ovary superior, ± ovoid, 2.5—4 × 2.4—3 mm, green, glabrous, 1–chambered with many ovules attached typically to 4 placentae on outer side; style short; stigmas (3—)4, ascending to spreading, from narrow at base lobed and broadly fan–shaped, 3—4 mm long and wide, fleshy, yellow–green, crisped, wavy, lobes with jagged margin, persistent.
Fruit capsule, loculicidal, dehiscing by (3)4 valves reflexed from top downward, 30+–seeded, ovoid, 9—11 × 6.5—8 mm, glabrous; pedicel > fruit at base of inflorescence decreasing upward with pedicel < fruit approaching tip.
Seed with long, silky, white hairs attached at 1 end (comose); seed body before drying oblanceoloid to oblong, 3.5—4 × 0.8—1.1 mm, white, drying flattened, somewhat twisted, and darker, appearing glabrous on faces.
A. C. Gibson