According to observations of naturalists and beekeepers.
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This plant is present in at least 6 states/provinces in this country.
Richardson's willow is an erect, much-branched shrub usually forming dense clumps 3 to 6 feet (1-2 m) tall, sometimes to 15 feet (4.5 m). Young twigs are stout and densely hairy; older twigs are glabrous. The bark of Richardson's willow is smooth. Shrubs are composed of light wood that becomes brittle with age; a single trunk rarely survives 60 years. In silty loam containing much organic matter, the roots of Richardson's willow are numerous in the top 7.5 inches (19 cm) of soil, but become less abundant at 9 inches (23 cm). In the frozen ground, roots of Richardson's willow do not exceed 9 inches (23 cm), but as the ground thaws roots will grow up to 17 inches (43 cm) deep.
Richardson's willow flowers from May through July or August. The fruit ripens soon after flowering, followed by seed dispersal in early to midsummer.
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)
Rubus spectabilis (aka: Salmonberry)
Salix discolor (aka: Pussy willow, American pussy willow, Glaucous willow, Large pussy willow)
Salix exigua (aka: Narrowleaf willow, Coyote willow)
Prunus cerasus (aka: Sour cherry, Tart cherry, Dwarf cherry, Montmorency cherry)
Crataegus douglasii (aka: Black hawthorn, Douglas hawthorn, River hawthorn, Western thornapple)
Populus tremuloides (aka: Quaking aspen, Trembling aspen, Aspen, American aspen, Mountain aspen, Golden aspen, Trembling poplar, White poplar, Popple, Alamo Blanco)
Salix scouleriana (aka: Scouler's willow, Upland willow)
Acer circinatum (aka: Vine maple)
Prunus emarginata (aka: Bitter cherry)
Malus fusca (aka: Oregon crab, Oregon crab apple, Pacific crab apple, Western crab apple)
Salix arbusculoides (aka: Littletree willow)
Salix bebbiana (aka: Bebb willow, Beak willow, Beaked willow, Long-beaked willow, Diamond willow, Chaton, Petit Minou, Smooth Bebb willow)
Malus domestica (aka: Pyrus pumila, Malus pumila, Apple)
Acer macrophyllum (aka: Bigleaf maple, Big-leaf maple, Oregon maple)
Acer platanoides (aka: Norway maple)
Rubus ursinus (aka: California blackberry, California dewberry, California grapeleaf dewberry, Douglasberry, Pacific blackberry)