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Humboldt's willow

skeleton-leaf willow

Habit Plants 0.01–0.07 m, (dwarf), forming clonal mats by rhizomes.
Stems

trailing;

branches red-brown or yellow-brown, glabrous;

branchlets red-brown, glabrous.

Leaves

(prominently marcescent, becoming skeletonized);

stipules absent or rudimentary;

petiole (deeply grooved or convex to flat adaxially), 1.2–3.2(–4.8) mm, (sparsely pubescent adaxially);

largest medial blade amphistomatous, (2 pairs secondary veins arising at or close to base, arcing toward apex), elliptic, broadly elliptic, obovate, subcircular, or circular, 7–15 × 3–11 mm, 1.1–2.5(–3.5) times as long as wide, base convex or cuneate, margins flat, entire, sometimes ciliate, apex convex, rounded, or retuse, abaxial surface not glaucous, glabrous, midrib sometimes pilose, hairs long, straight, wavy, or crinkled, adaxial highly glossy, glabrous;

proximal blade margins entire;

juvenile blade (green), glabrous abaxially or ciliate.

Staminate flowers

abaxial nectary absent, adaxial nectary narrowly oblong or oblong, 0.4–1.1 mm;

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

anthers ellipsoid or obovoid, 0.3–0.5 mm.

Pistillate flowers

abaxial nectary absent, adaxial nectary oblong or narrowly oblong, 0.4–1.6 mm, shorter than or equal to stipe;

stipe 0.4–1.4 mm;

ovary pyriform, sparsely to moderately densely short-silky or villous, at least on beaks, hairs ribbonlike, beak slightly bulged below styles;

ovules 12 per ovary;

styles connate or slightly distinct distally, 0.3–1 mm;

stigmas flat, abaxially non-papillate with rounded tip, or slenderly to broadly cylindrical, 0.16–0.34–0.52 mm.

Capsules

2.9–4.8 mm.

Salix

humboldtiana Willdenow: Humboldt willow is not known to occur in the flora area.

It

is characterized by: trees, 4–25 m;

branches highly brittle at base, bud-scale margins distinct and overlapping adaxially;

stipules on late leaves rudimentary or foliaceous;

largest medial leaf blade usually linear, abaxial surface not glaucous, adaxial dull; pistillate bract deciduous after flowering;

stamens 3–7;

capsules with distinct, often raised, white veins.;

it occurs throughout much of Mexico to central Chile.

Catkins

staminate 10–35 × 6–10 mm, flowering branchlet 1–11 mm; pistillate moderately densely flowered, stout or subglobose, 12–38 × 5–11 mm, flowering branchlet 3–14 mm;

floral bract brown, black, or bicolor, 1–1.3 mm, apex rounded, entire, abaxially sparsely hairy, hairs straight or wavy.

2n

= 38.

Salix humboldtiana

Salix phlebophylla

Phenology Flowering Jun–Jul.
Habitat Arctic-alpine, dry Dryas-lichen tundra, polygonal tundra with stone stripes and dry raised centers, scree and colluvial slopes, grass-sedge tussock tundra, sedge meadows in drainage ways, dwarf birch thickets, granitic and sandstone substrates
Elevation 0-2100 m (0-6900 ft)
Distribution
from USDA
Mexico to central Chile
[BONAP county map]
from FNA
AK; NT; YT; e Asia (Chukotka, Russian Far East, arctic, e Siberia)
[BONAP county map]
Discussion

Salix humboldtiana is closely related to S. nigra in its generally narrow leaf blades, which are not glaucous abaxially. The two differ in the following characters: S. humboldtiana has leaf blades linear to sometimes narrowly oblong (10–28.6 times as long as wide), ovaries usually ovoid to ellipsoid, ovary walls often stomatiferous and with raised, white veins, and capsule valves relatively thick, slightly recurved. S. nigra has leaf blades usually narrowly lanceolate (6–13 times as long as wide), ovaries pyriform to obclavate, ovary walls neither stomatiferous nor notably veined, and capsule valves relatively thin and strongly recurved. Both species occur in Chihuahua, Mexico.

The report by R. I. Lonard et al. (1991) that specimens identified as Salix nigra from the lower Rio Grande, Texas, resemble S. humboldtiana in having strongly veined capsules suggests that S. humboldtiana, or intergrades with that species, may occur in Texas. Attempts to locate a voucher specimen were unsuccessful; because strongly veined capsules are diagnostic, further field study is indicated.

An earlier name, Salix chilensis Molina, has been applied to this species; it does not seem to pertain to this taxon (C. K. Schneider 1918).

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

Hybrids:

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

Salix phlebophylla × S. rotundifolia has hairy ovaries, some skeletonized leaves, a compact growth form that may lack rhizomes, and catkins with more than 15 flowers. It occurs on the Alaska arctic slope, outside the range of S. polaris.

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

Source FNA vol. 7, p. 34. FNA vol. 7, p. 74.
Parent taxa Salicaceae > Salix > subg. Protitea > sect. Humboldtianae Salicaceae > Salix > subg. Chamaetia > sect. Myrtosalix
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. 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. 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. 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. 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
Name authority Willdenow Andersson: Proc. Amer. Acad. Arts 4: 72. (1858)
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