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.
Rubus ursinus (aka: California blackberry, California dewberry, California grapeleaf dewberry, Douglasberry, Pacific blackberry)
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)
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)
Salix brachycarpa (aka: Shortfruit willow, Barren-ground willow, Small-fruit sand dune willow, Small-fruit willow)
Rubus parviflorus (aka: Thimbleberry, Western thimbleberry)
Rubus armeniacus (aka: Himalayan blackberry, Rubus discolor, Rubus procerus)
Rubus idaeus (aka: Raspberry, Black-haired red raspberry, Brilliant red raspberry, American red raspberry, Red raspberry, Smoothleaf red raspberry, Wild raspberry, Wild red raspberry, Grayleaf raspberry)
Echium vulgare (aka: Viper's bugloss, Blueweed, Blue thistle)
Brassica rapa (aka: Field mustard, Common mustard, Wild mustard, Wild turnip, Forage turnip, Wild rutabaga, Birdsrape mustard, Rape mustard)
Asclepias syriaca (aka: Сommon milkweed, Butterfly flower, Silkweed, Silky swallow-wort, Virginia silkweed)
Agastache foeniculum (aka: Giant hyssop, Blue giant hyssop, Anise hyssop, Fragrant giant hyssop, Lavender giant hyssop)
Chamaenerion angustifolium (aka: Fireweed, Great willowherb, Rosebay willowherb, Saint Anthony's Laurel, French-willow)
Borago officinalis (aka: Borage, Starflower, Common borage, Cool-tankard, Tailwort)
Cucumis melo (aka: Cantaloupe, Rockmelon, Sweet melon, Spanspek, Honeydew melon, Honeymelon, Crenshaw, Casaba)
Rhus glabra (aka: Smooth sumac, Common sumac, Rocky Mountain sumac, Red sumac, Western sumac, White sumac)
Hyssopus officinalis (aka: Hyssop)