1. Populus heterophylla Linnaeus, Sp. Pl. 2: 1034. 1753.
Swamp or downy poplar Swamp or downy poplar
Plants to 28 m, 
1. Populus heterophylla Linnaeus, Sp. Pl. 2: 1034. 1753.
Swamp or downy poplar Swamp or downy poplar
Plants to 28 m, 12 dm diam.; not obviously heterophyllous. Bark reddish brown to brownish gray, deeply furrowed. Branchlets reddish brown, becoming grayish by third year, round to 5-angled, 3-6 mm diam., very coarse, thinly tomentose to glabrate. Winter buds reddish brown, pubescent, slightly resinous; terminal buds 4-7 mm; flowering buds separated on branchlets, 4-7 mm. Leaves: petiole round distally, (1-) 4-8(-12) cm, 1/2 blade length, (tomentose to glabrate); blade ovate, (3.5-)9-20(-24) × (3.5-)7.5-12.5(-19) cm, w/l = 2/3-3/4, base deeply cordate to subsagittate, basilaminar glands 0 or 2, round, margins not translucent, not ciliate, apex obtuse to apiculate, abaxial surface pale green, pubescent to partly glabrate, retaining tomentum at least basally and on midvein, adaxial dark green, glabrous; preformed and neoformed blade margins finely and unevenly crenate-serrate throughout, teeth 30-60 on each side, sinuses 0.3-1 mm deep. Catkins sparsely 10-15(-45)-flowered, 4.5-8(-18 in fruit) cm; floral bract apex deeply cut, not ciliate (pubescent abaxially). Pedicels (1-)5-10(-18 in fruit) mm. Flowers: discs (caducous), cup-shaped, not obviously oblique, toothed, 1.5-2.5(-4) mm diam.; stamens 15-35; anthers apiculate; ovary 3-carpelled, ovoid to spherical; stigmas 2-4, convoluted, expanded, erect. Capsules ovoid, 8-14 mm, glabrous, 3-valved. Seeds 6-9 per placenta.
Flowering Apr; fruiting May-Jun. Nyssa-Taxodium swamps, drainage ditches, natural and artificial wet depressions, coastal plains, central lowlands, piedmont along major streams; 0-200(-400) m; Ont.; Ala., Ark., Conn., Del., D.C., Fla., Ga., Ill., Ind., Ky., La., Md., Mich., Miss., Mo., N.J., N.Y., N.C., Ohio, S.C., Tenn., Va.
Populus heterophylla is widespread and uncommon in most of its range, which is entirely included within that of P. de