6. Populus fremontii S. Watson, Proc. Amer. Acad. Arts. 10: 350. 1875.
Fremont cottonwood
Plants to 30 m, 37 dm diam.; strongly heterophyllous, (often 2 or more trunks near base). Bark pale tan, deeply furrowed. Branchlets tannish brown, becoming paler tan to bone- white by third year, round, 1-3(-5) mm diam., slender to coarse, glabrous, glabrate, or sparsely to densely hairy, (yellowish). Winter buds yellow-brown, usually densely stiffly hairy, resinous (resin yellow); terminal buds (4-)7-11(-14) mm; flowering buds separated on branchlets, (5-)11-18(-22) mm. Leaves: petiole distally flattened at right angle to plane of blade, 1-6(-9) cm, 3/5-3/4 blade length; blade rhombic-ovate to broadly triangular-ovate, (1.5-)4-8 (-14) × (1.5-)3-8(-11) cm, w/l = 3/5-1/1, base cuneate to truncate or cordate, basilaminar glands 0, margins translucent, ciliate, apex short- to long-acuminate, surfaces yellowish green, resin stains not evident, glabrous or densely hairy; preformed blade margins coarsely crenate-serrate midblade, teeth 3-10(-15) on each side (graded, rounded), sinuses (0.2-)0.5-4(-5.5) mm deep; neoformed blade margins finely crenate-serrate much of margin, teeth (10-)20-30(-45) on each side, sinuses 0.1-1 mm deep. Catkins loosely (10-)15-25(-35)-flowered, (3-)4.5-10(-14 in fruit) cm; floral bract apex deeply cut, not ciliate. Pedicels 1-4 (-5.5 in fruit) mm. Flowers: discs broadly cup-shaped, not obviously oblique, entire, (2.5-)4-7(-9) mm diam.; stamens (30-)40-60(-70); anthers truncate; ovary 2-4-carpelled, spherical; stigmas 2-4, flat, platelike, expanded. Capsules spherical, (5-)6-11 mm, glabrous, 2-4-valved. Seeds 9-15(-25) per placenta. 2n = 38.
Subspecies 2 (2 in the flora): sw United States, n Mexico.
