The green links below add additional plants to the comparison table. Blue links lead to other Web sites.
enable glossary links

least willow, round-leaf willow

Coulter willow, Sitka willow

Habit Plants 0.005–0.05 m, (dwarf), forming clones by rhizomes. Shrubs or trees, 1–8 m, (sometimes forming clones by stem fragmentation).
Stems

erect;

branches yellow-green, yellow-brown, or gray-brown, glabrous;

branchlets yellow-brown or red-brown, glabrous;

branches and branchlets sometimes weakly glaucous.

branches (sometimes highly brittle at base), yellow-brown or red-brown, not glaucous, glabrous or pilose;

branchlets yellow-brown, gray-brown, or red-brown, densely short-silky, velvety, or villous, (buds caprea-type or intermediate).

Leaves

(marcescent but not skeletonized), stipules usually absent or rudimentary, rarely present on late ones;

petiole (convex, or shallowly to deeply grooved, flat), 0.4–4.6(–5.5) mm, (glabrous adaxially);

largest medial blade (2 pairs of secondary veins arising at or close to base, arcing toward apex) broadly elliptic, subcircular, or circular, 1.9–16.3 × 3–10.5 mm, 0.84–1.17(–2.53) times as long as wide, base rounded or convex, margins flat, entire, ciliate, apex retuse, rounded, convex, or acute, abaxial surface glabrous, adaxial highly glossy, glabrous;

proximal blade margins entire;

juvenile blade glabrous or puberulent.

stipules absent or rudimentary on early ones, rudimentary or foliaceous on late ones, apex acute;

petiole convex to flat, or shallowly grooved adaxially, 3–13(–16) mm, tomentose or velvety adaxially;

largest medial blade elliptic, narrowly oblanceolate, oblanceolate, or obovate, 31–70–120 × 17–48 mm, 2.1–3.1–4 times as long as wide, base cuneate or convex, margins slightly revolute or flat, strongly revolute proximally, entire, irregularly serrate, or sinuate, (glands submarginal or epilaminal), apex acuminate or convex, abaxial surface not evidently glaucous, (obscured by hairs), densely short-silky, woolly, or silky-woolly, hairs straight, wavy, or curved, adaxial slightly glossy (sometimes dull and glaucous), pilose or moderately densely short-silky;

proximal blade margins entire or shallowly serrulate;

juvenile blade green, densely long-silky or woolly abaxially, (sparsely silky-tomentose adaxially), hairs white.

Staminate flowers

abaxial nectary 0.5–1 mm, adaxial nectary narrowly oblong or oblong, 0.8–1.4 mm, nectaries distinct;

filaments distinct or connate less than 1/2 their lengths, glabrous;

anthers ellipsoid or globose, 0.4–0.6 mm.

adaxial nectary narrowly oblong, oblong, ovate, or flask-shaped, 0.4–1.3 mm;

stamens 1;

filaments distinct, glabrous;

anthers purple turning yellow, shortly cylindrical, 0.5–0.7 mm.

Pistillate flowers

abaxial nectary present or absent, adaxial nectary usually narrowly oblong or oblong, sometimes flask-shaped, 0.8–2 mm, longer than stipe;

stipe 0.4–0.8 mm;

ovary pyriform, glabrous or puberulent, (hairs in patches, especially on beak), beak slightly bulged below styles;

ovules 7–17 per ovary;

styles connate or slightly distinct distally, 0.5–1 mm;

stigmas flat, abaxially non-papillate with pointed tip, or slenderly or broadly cylindrical, 0.28–0.6 mm.

adaxial nectary square, ovate, or flask-shaped, 0.5–0.9 mm, shorter to longer than stipe;

stipe 0.4–1.4 mm;

ovary ovoid to pyriform, long- or short-silky or villous, beak sometimes slightly bulged below styles;

ovules 14–20 per ovary;

styles 0.4–0.8 mm;

stigmas flat, abaxially non-papillate with rounded tip, or broadly cylindrical, 0.16–0.28–0.4 mm.

Capsules

3.8–8.3 mm.

3.5–5.6 mm.

Catkins

from subterminal buds; staminate subglobose, stout, or indeterminate, 3.3–18.5 × 2.5–12 mm, flowering branchlet 0.5–9 mm; pistillate moderately densely to loosely flowered (2–15 flowers), stout, subglobose, globose, or indeterminate, 4.5–35 × 2–17 mm, flowering branchlet 0.5–22 mm;

floral bract brown, 1.6–2.8 mm, apex rounded or retuse, entire, abaxially sparsely hairy or ciliate, hairs usually wavy, crinkled or curly, rarely straight.

flowering just before or as leaves emerge; staminate slender or stout, (17–)22–54 × 8–15 mm, flowering branchlet 1–9 mm; pistillate moderately densely flowered, slender to stout, 25–73(–115 in fruit) × 5–15 mm, flowering branchlet 1–20 mm;

floral bract tawny to dark brown, 1.4–2.4 mm, apex rounded or acute, abaxially hairy, hairs straight or wavy.

2n

= 38.

Salix rotundifolia

Salix sitchensis

Phenology Flowering early Apr-mid Jun (Mar in California).
Habitat Tidal swamps and marshes, coastal fog belts and headlands, sand dunes, springs, gravelly streambeds and deltas, glacial moraines, avalanche tracks, dry canyons, clearings and edges of forests, shade tolerant
Elevation 0-1800 m (0-5900 ft)
Distribution
from FNA
AK; MT; WY; NT; YT; e Asia
[WildflowerSearch map]
[BONAP county map]
from FNA
AK; CA; ID; MT; OR; WA; AB; BC
[WildflowerSearch map]
[BONAP county map]
Discussion

Varieties 2 (2 in the flora).

Salix rotundifolia is closely related to S. polaris, from which it can be separated by its glabrous ovaries and fewer-flowered catkins. They also differ somewhat in leaf venation: S. rotundifolia typically having three main veins arising from the leaf base, often only one or two pair of secondary veins, and no or indistinct tertiary veins; S. polaris typically having pinnate venation, multiple secondary veins, and distinct tertiary veins. Salix rotundifolia consists of two varieties, the diploid var. dodgeana and the hexaploid var. rotundifolia. In general, var. dodgeana is a high alpine species in the southern cordillera of Wyoming and Montana, the St. Elias Mountains in Alaska and Yukon, the Mackenzie Mountains, Northwest Territories, and the Richardson Mountains, Yukon Territory. A diploid specimen of S. rotundifolia in the Cherski Mountains, Yakutia, Russia (B. A. Jurtzev and P. G. Zhukova 1982), which fits var. dodgeana in its 2–3-flowered catkins, relatively small leaves (3.5 × 3.9 mm), and small stomata (490 µm2), may represent an ancestral population. Variety rotundifolia usually occurs at lower elevations in Alaska and in easternmost Chukotka and Wrangel Island, Russia, but elevation separation is not distinct. There is a general correlation between stomatal size and ploidal level (W. Buechler, pers. comm.), but relatively large stomata in some diploid specimens of S. rotundifolia indicates a need for further cytological study. For the present, it is best to recognize the two cytotypes as varieties.

Hybrids:

Salix rotundifolia forms natural hybrids with S. arctica, S. phlebophylla, and S. polaris.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Ovary hairiness in some Salix sitchensis populations varies from uniformly hairy to glabrescent, with intermediates with patchy or streaky hairiness. All three variations can occur together and do not seem to indicate hybridization.

Both Salix sitchensis and S. scouleriana have similar variants with leaves having very densely curly hairs on abaxial surfaces [S. sitchensis forma coulteri (Andersson) Jepson and S. scouleriana forma poikila (C. K. Schneider) C. K. Schneider]. Plants resembling S. drummondiana but with similar indumentum probably are hybrids with S. alaxensis (see 84. S. drummondiana). The coulteri taxon resembles S. delnortensis in having stipules with adaxial surfaces glabrous and very sparsely glandular toward the base, densely hairy abaxially, and with gland-dotted margins; its branchlets have wavy to crinkly hairs. The possible hybrid origin of S. delnortensis needs study (R. D. Dorn 2000).

Hybrids:

Salix sitchensis forms natural hybrids with S. alaxensis var. longistylis and S. melanopsis. Hybridization with S. geyeriana reported by J. K. Henry (1915) is not based on convincing specimens.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Key
1. Pistillate catkins: (3-)4-7-15 flowers; largest medial blades 4.5-8-16.3 mm, 0.92-1.23-2.27 times as long as wide; petioles 0.5-2-4.6 (-5.5) mm; floral bracts: hairs usually wavy, some straight, curly, or crinkled, exceeding bract by 0.32-0.71-1.25(-2.4) mm; pistillate flowers: abaxial nectaries present or absent; 2n = 114.
var. rotundifolia
1. Pistillate catkins: 2-4-9 flowers; largest medial blades 2.9-6.1-7.4 mm, 0.84-1.5-2.2 times as long as wide; petioles 0.4-1.1-2.8 mm; floral bracts: hairs usually wavy, crinkled, or curly, rarely straight, exceeding bract by 0.1-0.37-0.75 mm; pistillate flowers: abaxial nectaries absent; 2n = 38.
var. dodgeana
Source FNA vol. 7, p. 69. FNA vol. 7, p. 159.
Parent taxa Salicaceae > Salix > subg. Chamaetia > sect. Herbella Salicaceae > Salix > subg. Vetrix > sect. Sitchenses
Sibling taxa
S. alaxensis, S. alba, S. amygdaloides, S. arbusculoides, S. arctica, S. arctophila, S. argyrocarpa, S. arizonica, S. athabascensis, S. atrocinerea, S. aurita, S. babylonica, S. ballii, S. barclayi, S. barrattiana, S. bebbiana, S. bonplandiana, S. boothii, S. brachycarpa, S. breweri, S. calcicola, S. candida, S. caprea, S. caroliniana, S. cascadensis, S. chamissonis, S. chlorolepis, S. cinerea, S. columbiana, S. commutata, S. cordata, S. daphnoides, S. delnortensis, S. discolor, S. drummondiana, S. eastwoodiae, S. elaeagnos, S. eriocephala, S. euxina, S. exigua, S. famelica, S. farriae, S. floridana, S. fuscescens, S. geyeriana, S. glauca, S. gooddingii, S. hastata, S. herbacea, S. hookeriana, S. humboldtiana, S. humilis, S. interior, S. irrorata, S. jejuna, S. jepsonii, S. laevigata, S. lasiandra, S. lasiolepis, S. lemmonii, S. ligulifolia, S. lucida, S. lutea, S. maccalliana, S. melanopsis, S. monochroma, S. monticola, S. myricoides, S. myrsinifolia, S. myrtillifolia, S. nigra, S. niphoclada, S. nivalis, S. nummularia, S. orestera, S. ovalifolia, S. pedicellaris, S. pellita, S. pentandra, S. petiolaris, S. petrophila, S. phlebophylla, S. planifolia, S. polaris, S. prolixa, S. pseudomonticola, S. pseudomyrsinites, S. pulchra, S. purpurea, S. pyrifolia, S. raupii, S. reticulata, S. richardsonii, S. scouleriana, S. sericea, S. serissima, S. sessilifolia, S. setchelliana, S. silicicola, S. sitchensis, S. sphenophylla, S. stolonifera, S. taxifolia, S. thurberi, S. tracyi, S. triandra, S. turnorii, S. tweedyi, S. tyrrellii, S. uva-ursi, S. vestita, S. viminalis, S. wolfii, S. ×fragilis, S. ×jesupii, S. ×pendulina, S. ×sepulcralis, S. ×smithiana
S. alaxensis, S. alba, S. amygdaloides, S. arbusculoides, S. arctica, S. arctophila, S. argyrocarpa, S. arizonica, S. athabascensis, S. atrocinerea, S. aurita, S. babylonica, S. ballii, S. barclayi, S. barrattiana, S. bebbiana, S. bonplandiana, S. boothii, S. brachycarpa, S. breweri, S. calcicola, S. candida, S. caprea, S. caroliniana, S. cascadensis, S. chamissonis, S. chlorolepis, S. cinerea, S. columbiana, S. commutata, S. cordata, S. daphnoides, S. delnortensis, S. discolor, S. drummondiana, S. eastwoodiae, S. elaeagnos, S. eriocephala, S. euxina, S. exigua, S. famelica, S. farriae, S. floridana, S. fuscescens, S. geyeriana, S. glauca, S. gooddingii, S. hastata, S. herbacea, S. hookeriana, S. humboldtiana, S. humilis, S. interior, S. irrorata, S. jejuna, S. jepsonii, S. laevigata, S. lasiandra, S. lasiolepis, S. lemmonii, S. ligulifolia, S. lucida, S. lutea, S. maccalliana, S. melanopsis, S. monochroma, S. monticola, S. myricoides, S. myrsinifolia, S. myrtillifolia, S. nigra, S. niphoclada, S. nivalis, S. nummularia, S. orestera, S. ovalifolia, S. pedicellaris, S. pellita, S. pentandra, S. petiolaris, S. petrophila, S. phlebophylla, S. planifolia, S. polaris, S. prolixa, S. pseudomonticola, S. pseudomyrsinites, S. pulchra, S. purpurea, S. pyrifolia, S. raupii, S. reticulata, S. richardsonii, S. rotundifolia, S. scouleriana, S. sericea, S. serissima, S. sessilifolia, S. setchelliana, S. silicicola, S. sphenophylla, S. stolonifera, S. taxifolia, S. thurberi, S. tracyi, S. triandra, S. turnorii, S. tweedyi, S. tyrrellii, S. uva-ursi, S. vestita, S. viminalis, S. wolfii, S. ×fragilis, S. ×jesupii, S. ×pendulina, S. ×sepulcralis, S. ×smithiana
Subordinate taxa
S. rotundifolia var. dodgeana, S. rotundifolia var. rotundifolia
Synonyms S. coulteri, S. sitchensis var. parvifolia
Name authority Trautvetter: Nouv. Mém. Soc. Imp. Naturalistes Moscou 2: 304, plate 11. (1832) Sanson ex Bongard: Mém. Acad. Imp. Sci. St.-Pétersbourg, Sér. 6, Sci. Math. 2: 162. (1832)
Web links