According to observations of naturalists and beekeepers.
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Echium vulgare — known as viper's bugloss and blueweed — is a species of flowering plant in the borage family Boraginaceae. It is native to most of Europe, and western and central Asia and it occurs as an introduced species in North America.
This plant is present in at least 52 states/provinces in this country.
It is a biennial or monocarpic perennial plant growing to 30–80 cm tall, with rough, hairy, oblanceolate leaves. The flowers start pink and turn vivid blue and are 15–20 mm in a branched spike, with all the stamens protruding. The pollen is blue but the filaments of the stamens remain red, contrasting against the blue flowers.
It flowers between June and August.
Acer saccharinum (aka: Silver maple, Soft maple)
Salix nigra (aka: Black willow, Swamp willow, Southwestern black willow, Gulf black willow, Scythe-leaved willow)
Cercis canadensis (aka: Eastern redbud, Redbud, Cersis Reniformis)
Malus angustifolia (aka: American crab apple, Buncombe crab apple, Crabtree, Narrowleaf crab, Narrowleaf crab apple, Southern crab, Southern crab apple)
Aronia arbutifolia (aka: Red chokeberry)
Ulmus americana (aka: American elm, White elm, Water elm, Soft elm, Florida elm)
Prunus americana (aka: American plum, Goose plum, River plum, Wild plum)
Salix discolor (aka: Pussy willow, American pussy willow, Glaucous willow, Large pussy willow)
Pyrus communis (aka: European pear, Common pear)
Celtis laevigata (aka: Hackberry, Sugarberry, Lowland hackberry, Sugar hackberry, Arizona sugarberry, Netleaf hackberry, Small's hackberry, Southern hackberry, Texas sugarberry)
Acer negundo (aka: Boxelder, Western boxelder, Arizona boxelder, California boxelder, Texas boxelder, Interior boxelder, Violet boxelder)
Vaccinium corymbosum (aka: Highbush blueberry, High-bush blueberry, Northern highbush blueberry, Tall blueberry, Rabbiteye blueberry, Blue huckleberry, Tall huckleberry, Swamp huckleberry, High blueberry, Swamp blueberry)
Malus domestica (aka: Pyrus pumila, Malus pumila, Apple)
Prunus cerasus (aka: Sour cherry, Tart cherry, Dwarf cherry, Montmorency cherry)
Malus coronaria (aka: Sweet crab apple, Garland crab, Alabama crab, Allegheny crab, American crab, Baltimore crab apple, Buncombe crab, Dawson crab, Dunbar crab, Fragrant crab, Garland tree, Lanceleaf crab apple, Missouri crab, Sweet-scented crab, Sweet wild crab, Wild crab, Wild sweet crab, Wild Crab Apple)
Populus tremuloides (aka: Quaking aspen, Trembling aspen, Aspen, American aspen, Mountain aspen, Golden aspen, Trembling poplar, White poplar, Popple, Alamo Blanco)
Liriodendron tulipifera (aka: Tuliptree, Blue-poplar, Tulip-poplar, Yellow-poplar, Yellow wood)
Acer saccharum (aka: Sugar maple, Rock maple, Hard maple)
Celtis occidentalis (aka: Common hackberry, Bastard elm, Nettle-tree, Northern hackberry)
Ilex opaca (aka: American holly, Dune holly, Hummock holly, Scrub holly)
Acer platanoides (aka: Norway maple)
