Mackenzie’s willow

Salix cordata Muhlenberg var. mackenzieana Hooker; S. eriocephala Michaux subsp. mackenzieana (Hooker) Dorn; S. mackenzieana (Hooker) Barratt ex Andersson; S. mackenzieana var. macrogemma C. R. Ball; S. rigida Muhlenberg var. mackenzieana (Hooker) Cronquist; S. rigida var. macrogemma (C. R. Ball) Cronquist

Shrubs, 1-5 m. Stems: branches gray-brown or red-brown, not or weakly glaucous, (with sparkling wax crystals), glabrous or moderately villous; branchlets yellow-green, or yellow-brown to red-brown, glabrous or sparsely to moderately densely velvety, (inner membranaceous bud-scale layer free, separating from outer layer). Leaves: stipules foliaceous, apex acuminate to rounded; petiole convex to flat adaxially, 6-12 mm, glabrous or pilose adaxially; largest medial blade narrowly oblong, narrowly elliptic, lanceolate, or obovate, 50-150 × 10-53 mm, 2.4-4.5 times as long as wide, base cordate, subcordate, rounded, or convex, margins flat, serrate, serrulate, or spinulose-serrulate, apex acuminate to acute, abaxial surface glaucous, glabrous, adaxial dull, glabrous, pilose, or sparsely pubescent, (sometimes adaxial stomata only along veins or apically); proximal blade margins entire; juvenile blade reddish or yellowish green, glabrous, pilose or sparsely long-silky abaxially, hairs white. Catkins flowering as leaves emerge; staminate slender or stout, 16-41 × 8-12 mm, flowering branchlet 0.5-3 mm; pistillate moderately densely to loosely flowered, slender or stout, 19-66 × 8-18 mm, flowering branchlet 0.5-6 mm; floral bract brown, 0.8-1.6 mm, apex acute or rounded, abaxially hairy mainly proximally, hairs straight or wavy. Staminate flowers: adaxial nectary oblong to narrowly oblong, 0.8-1 mm; filaments distinct or connate less than 1/2 their lengths, glabrous; anthers purple turning yellow, (ellipsoid), 0.5-0.6 mm. Pistillate flowers: adaxial nectary oblong, square, or flask-shaped, 0.3-0.8 mm, shorter than stipe; stipe 1.3-4.2 mm; ovary pyriform, glabrous, beak sometimes slightly bulged below styles; ovules 12-22 per ovary; styles 0.3-0.7 mm; stigmas flat, abaxially non-papillate with rounded tip, or 2 plump lobes, or slenderly cylindrical, 0.16-0.28-0.4 mm. Capsules 4-6 mm.

Flowering late Mar-late Jun. Along streams, lakes, springs, marsh margins, sandy-gravel, sandy or silty substrates; 100-2300 m; Alta., B.C., N.W.T., Yukon; Alaska, Calif., Idaho, Mont., Nev., Oreg., Wash., Wyo.