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.
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)
