Salix pentandra |
Salix rotundifolia |
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bay-leaf or bay or laurel willow, bay-leaf willow, laurel willow |
least willow, round-leaf willow |
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Habit | Shrubs or trees, 5–15 m. Stems: branches flexible at base, brownish or yellow-green, highly glossy, glabrous; branchlets yellow-green, red-brown, or brownish, glossy, glabrous. | Plants 0.005–0.05 m, (dwarf), forming clones by rhizomes. | ||||
Stems | erect; branches yellow-green, yellow-brown, or gray-brown, glabrous; branchlets yellow-brown or red-brown, glabrous; branches and branchlets sometimes weakly glaucous. |
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Leaves | stipules absent or rudimentary on early ones, rudimentary or foliaceous on late ones, apex rounded; petiole deeply to shallowly grooved adaxially, 5–15 mm, with pairs or clusters of spherical glands distally or throughout, glabrous adaxially; largest medial blade hypostomatous, narrowly elliptic, elliptic, or lanceolate, 50–135 × 20–50 mm, 2–4 times as long as wide, base convex, margins slightly revolute or flat, serrulate, apex acuminate, abaxial surface pale not glaucous, glabrous, adaxial highly glossy, glabrous; proximal blade margins entire or serrulate; juvenile blade reddish, glabrous abaxially. |
(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. |
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Staminate flowers | abaxial nectary 0.6–1.7 mm, adaxial nectary square, ovate, or oblong, 0.5–1.5 mm, nectaries distinct or ± connate and cup-shaped; stamens 4–10; filaments distinct, hairy on proximal 1/2; anthers ellipsoid or globose, 0.5–0.6 mm. |
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. |
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Pistillate flowers | (abaxial nectary present or absent), adaxial nectary oblong, square, or ovate, 0.4–0.8 mm, (nectaries distinct or connate and shallowly cup-shaped), shorter than or equal to stipe; stipe 0.5–1.6 mm; ovary pyriform, beak bulged below or tapering to styles; ovules 18–22 per ovary; styles connate or distinct, 0.4–0.6 mm; stigmas flat, abaxially non-papillate with rounded tip, or slenderly cylindrical, 0.4–0.6 mm. |
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. |
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Capsules | 6–9 mm. |
3.8–8.3 mm. |
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Catkins | staminate 27–81 × 9–13 mm, flowering branchlet 9–21 mm; pistillate moderately to densely flowered, slender or stout, 29–68 × 7–15 mm, flowering branchlet 9–42 mm; floral bract 2–4 mm, apex acute or rounded to truncate, entire or toothed, abaxially sparsely hairy (mainly proximally), hairs wavy or straight. |
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. |
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2n | = 76. |
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Salix pentandra |
Salix rotundifolia |
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Phenology | Flowering late May-mid Jun. | |||||
Habitat | Shores of streams and lakes, marshes, roadsides, waste places | |||||
Elevation | 0-2300 m (0-7500 ft) | |||||
Distribution |
AK; CO; CT; DC; IA; IL; KY; MA; MD; ME; MN; MT; NC; NE; NH; NJ; NY; OH; PA; RI; SD; VA; VT; WI; WY; AB; BC; MB; NB; NF; NS; ON; QC; SK; Eurasia [Introduced in North America]
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AK; MT; WY; NT; YT; e Asia
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Discussion | The Ohio occurrence is based on information from T. Cooperrider (pers. comm.). Only pistillate plants of Salix pentandra are known to occur in the flora area. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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.) |
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Key |
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Source | FNA vol. 7, p. 44. | FNA vol. 7, p. 69. | ||||
Parent taxa | Salicaceae > Salix > subg. Salix > sect. Salicaster | Salicaceae > Salix > subg. Chamaetia > sect. Herbella | ||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Name authority | Linnaeus: Sp. Pl. 2: 1016. (1753) | Trautvetter: Nouv. Mém. Soc. Imp. Naturalistes Moscou 2: 304, plate 11. (1832) | ||||
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