According to observations of naturalists and beekeepers.
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Scouler's willow is found primarily in the boreal forests of North America. It is widely distributed, occurring in Canada from the Yukon Territory south through British Columbia and east through Alberta, Saskatchewan and into Manitoba. In the United States, Scouler's willow occurs in Alaska, south through the western states and into Mexico in the mountains, and east to the Black Hills of South Dakota.
This plant is present in at least 18 states/provinces in this country.
Scouler's willow is generally a shrub, reaching 6 to 35 feet (2-10.6 m) in height. It occasionally grows as a tree and may reach 65 feet (20 m) in height. It is nonrhizomatous with a deep, extensive root system and may be multistemmed or have one main trunk with twigs spreading or ascending. It occurs in thickets and forests forming a tall shrub layer in young stands, but is intolerant of shade and can persist only under thin canopies. Beneath a tree canopy, Scouler's willow exhibits a tall, upright growth form, but if top-killed by disturbance it sprouts from the root crown creating a round growth form up to 16 feet (4.8 m) in diameter.
Scouler's willow has slender stems and branches reaching 4 to 8 inches (10-20 cm) in diameter at the base; smooth to flaky bark; and glabrous twigs. Leaves are glabrous to leathery, obovate to oblanceolate, and occasionally serrate. Twigs and leaf undersides of Scouler's willow are densely to thinly pubescent, with appressed, reddish hairs. Young twigs and vigorous shoots are often densely pubescent, while older stems are smooth. Stripped bark of Scouler's willow has a skunky odor.
A dioecious plant, Scouler's willow has large, single-scaled, floral winter buds, and lacks a terminal bud. Aments, expanding before or with leaves and quickly deciduous, are usually sessile or borne on a short spur shoot and flower profusely. Fruiting catkins are 0.8 to 2.4 inches long (2-6 cm) by 0.4 to 0.6 inches thick (1-1.5 cm) with dark floral bracts 4-5 mm long, one gland, and a capsule 5-8 mm long with dense, short hairs and a somewhat long beak.
Scouler's willow bud development begins in April, leafing out occurs in April and May, stem elongation occurs May through July, and leaf fall occurs in July through November. Earlier leaf fall is correlated with limited moisture availability. Flowering occurs in April through June, with fruit ripening and seed dispersal occurring in May through July.
Acer negundo (aka: Boxelder, Western boxelder, Arizona boxelder, California boxelder, Texas boxelder, Interior boxelder, Violet boxelder)
Pyrus communis (aka: European pear, Common pear)
Acer glabrum (aka: Rocky Mountain maple, Douglas maple, Greene's maple, New Mexico maple, Torrey maple)
Salix lucida (aka: Shining willow, Greenleaf willow, Tail-leaf willow, Whiplash willow, Pacific willow, Lance-leaf willow, Longleaf willow, Red willow, Western shining willow)
Salix exigua (aka: Narrowleaf willow, Coyote willow)
Prunus americana (aka: American plum, Goose plum, River plum, Wild plum)
Acer grandidentatum (aka: Bigtooth maple, Canyon maple, Western sugar maple)
Prunus cerasus (aka: Sour cherry, Tart cherry, Dwarf cherry, Montmorency cherry)
Crataegus douglasii (aka: Black hawthorn, Douglas hawthorn, River hawthorn, Western thornapple)
Prunus emarginata (aka: Bitter cherry)
Prunus pumila (aka: Sandcherry, Western sandcherry, Eastern sandcherry, Great Lakes sandcherry)
Salix bebbiana (aka: Bebb willow, Beak willow, Beaked willow, Long-beaked willow, Diamond willow, Chaton, Petit Minou, Smooth Bebb willow)
Salix scouleriana (aka: Scouler's willow, Upland willow)
Salix discolor (aka: Pussy willow, American pussy willow, Glaucous willow, Large pussy willow)
Malus domestica (aka: Pyrus pumila, Malus pumila, Apple)
Acer platanoides (aka: Norway maple)
Rubus ursinus (aka: California blackberry, California dewberry, California grapeleaf dewberry, Douglasberry, Pacific blackberry)
Salix amygdaloides (aka: Peachleaf willow, Peach leaf willow)
Salix drummondiana (aka: Drummond's willow, Beautiful willow, Blue willow)
Salix lemmonii (aka: Lemmon's willow, Lemmon willow)
Salix planifolia (aka: Diamondleaf willow, Planeleaf willow)
Salix boothii (aka: Booth's willow)
Robinia pseudoacacia (aka: Black locust, False acacia, Yellow locust, White locust, Green locust, Post locust, Falsa acacia, Robinia)
Rhamnus cathartica (aka: Common buckthorn, European buckthorn, Dahurian buckthorn)
Astragalus (aka: Milkvetch, Locoweed, Goat's-thorn)
Populus tremuloides (aka: Quaking aspen, Trembling aspen, Aspen, American aspen, Mountain aspen, Golden aspen, Trembling poplar, White poplar, Popple, Alamo Blanco)
Rubus laciniatus (aka: Cutleaf blackberry, Evergreen blackberry, Slashed blackberry)
Salix lutea (aka: Yellow willow)
Salix geyeriana (aka: Geyer willow, Silver willow)
Allium schoenoprasum (aka: Chives)
Brassica napus (aka: Rapeseed)
Sinapis arvensis (aka: Charlock mustard, California rape, Charlock, Corn mustard, Canola, Kaber mustard, Rapeseed mustard)
Celtis occidentalis (aka: Common hackberry, Bastard elm, Nettle-tree, Northern hackberry)
Gleditsia triacanthos (aka: Honey locust, Honey shucks locust, Common honeylocust, Sweet bean locust)
Prunus pensylvanica (aka: Pin cherry, Fire cherry, Bird cherry)
Cirsium arvense (aka: Creeping Thistle, Canada thistle, Field thistle, California thistle, Lettuce from hell thistle, Corn thistle, Cursed thistle, Green thistle, Hard thistle, Perennial thistle, Prickly thistle, Small-flowered thistle, Way thistle, Stinger-needles)
Prunus virginiana (aka: Chokecherry, Western chokecherry, Common chokecherry, Black chokecherry)