According to observations of naturalists and beekeepers.
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Chamaenerion angustifolium, known in North America as fireweed, in some parts of Canada as great willowherb, in Britain and Ireland as rosebay willowherb, and traditionally known as Saint Anthony's Laurel amongst other variants, is a perennial herbaceous flowering plant in the willowherb family Onagraceae. It is also known by the synonyms Chamerion angustifolium and Epilobium angustifolium. It is native throughout the temperate Northern Hemisphere, including large parts of the boreal forests.
This plant is present in at least 19 states/provinces in this country.
The reddish stems of this herbaceous perennial are usually simple, erect, smooth, 0.5–2.5 m (1½–8 feet) high with scattered alternate leaves. The leaves are spirally arranged, entire, narrowly lanceolate, and pinnately veined, the secondary leaf veins anastomosing, joining together to form a continuous marginal vein just inside the leaf margins.
The inflorescence is asymmetrical terminal raceme that blooms progressively from bottom to top, producing a gracefully tapered shape. The flowers are 2 to 3 cm in diameter, slightly asymmetrical, with four magenta to pink petals and four narrower pink sepals behind. The protruding style has four stigmas.
The upright, reddish-brown linear seed capsule splits from the apex and curls open. It bears many minute brown seeds, about 300 to 400 per capsule, and 80,000 per plant. The seeds have silky hairs to aid wind dispersal and are very easily spread by the wind, often becoming a weed and a dominant species on disturbed ground. Once established, the plants also spread extensively by underground roots, an individual plant eventually forming a large patch.
The flowers are visited by a wide variety of insects.
Aronia arbutifolia (aka: Red chokeberry)
Pyrus communis (aka: European pear, Common pear)
Acer negundo (aka: Boxelder, Western boxelder, Arizona boxelder, California boxelder, Texas boxelder, Interior boxelder, Violet boxelder)
Salix lucida (aka: Shining willow, Greenleaf willow, Tail-leaf willow, Whiplash willow, Pacific willow, Lance-leaf willow, Longleaf willow, Red willow, Western shining willow)
Amelanchier arborea (aka: Common serviceberry, Downy serviceberry, Juneberry, Shadbush, Shadblow, Sugarplum)
Acer saccharum (aka: Sugar maple, Rock maple, Hard maple)
Prunus cerasus (aka: Sour cherry, Tart cherry, Dwarf cherry, Montmorency cherry)
Populus tremuloides (aka: Quaking aspen, Trembling aspen, Aspen, American aspen, Mountain aspen, Golden aspen, Trembling poplar, White poplar, Popple, Alamo Blanco)
Salix bebbiana (aka: Bebb willow, Beak willow, Beaked willow, Long-beaked willow, Diamond willow, Chaton, Petit Minou, Smooth Bebb willow)
Acer rubrum (aka: Red maple, Scarlet maple)
Ulmus americana (aka: American elm, White elm, Water elm, Soft elm, Florida elm)
Malus domestica (aka: Pyrus pumila, Malus pumila, Apple)
Acer platanoides (aka: Norway maple)
Catalpa speciosa (aka: Northern catalpa, Hardy catalpa, Western catalpa, Cigar tree, Catawba-tree, Bois chavanon)
Acer pensylvanicum (aka: Striped maple, Moosewood, Goosefoot maple, Whistlewood)
Rubus canadensis (aka: Smooth blackberry, Thornless blackberry, Canadian blackberry, Smooth highbush blackberry)
Robinia pseudoacacia (aka: Black locust, False acacia, Yellow locust, White locust, Green locust, Post locust, Falsa acacia, Robinia)
Ajuga reptans (aka: Bugle, Blue bugle, Bugleherb, Bugleweed, Carpetweed, Carpet bugleweed, Common bugle, St. Lawrence plant)
Acer spicatum (aka: Mountain maple, Low maple, Moose maple, Water maple, Plaine batarde, Fouereux)
Astragalus (aka: Milkvetch, Locoweed, Goat's-thorn)
Brassica napus (aka: Rapeseed)
Allium schoenoprasum (aka: Chives)
Sinapis arvensis (aka: Charlock mustard, California rape, Charlock, Corn mustard, Canola, Kaber mustard, Rapeseed mustard)
Aronia melanocarpa (aka: Black chokeberry, Rowan, Mountain Ash, Sorbus)
Prunus serotina (aka: Black cherry, Wild black cherry, Rum cherry, Mountain black cherry, Wild cherry)
Prunus pensylvanica (aka: Pin cherry, Fire cherry, Bird cherry)
Calendula officinalis (aka: Marigold, Calendula, Pot marigold, English marigold)
Rhamnus cathartica (aka: Common buckthorn, European buckthorn, Dahurian buckthorn)
