Fireweed, also called rosebay willowherb (Chamaenerion angustifolium syn. Chamerion angustifolium), cheers the northern wastes and wilds with spires of blooms leaning out from mountain slopes and massing in swathes where open sky prevails. Occasionally appearing as small, solitary individuals, it typically occurs in spreading drifts that bloom throughout summer, with a few blossoms hanging on until frost. In autumn, the rosy blooms give way to myriad satin-tufted seeds wafting near and far, prompting the adage, “When fireweed turns to cotton, summer will soon be forgotten”.
Fireweed blooms in single upright, unbranched clusters, or, racemes, from the tips of its stems, although it occasionally produces smaller spikes sprouting from leaf axils around the main inflorescence. Within a cluster, flowers ranging from few to as many as several hundred radiate from the central stem, opening in progression from the bottom upward. The loosely formed individual blossoms are formed in parts of four. Four medium to deep pink petals are separated by four narrow and similarly colored sepals1Sepals are modified leaves that enclose a flower bud before it opens and are usually green.. 
Eight stamens surround a stigma with four recurved tips. Soon after the pollinated blooms are spent, the inferior ovaries2An ovary is inferior when it is positioned entirely below the point at which all floral components join. behind them elongate and form thin, cylindrical seed capsules along the main stem, sharing its reddish hue and somewhat resembling the teeth of a comb. When ripe, the four-chambered seed capsules quickly pop open, their outer walls reflexing backward from the tip, lined with rows of as many as 300-400 tiny seeds per capsule, each with a silken tassel folded neatly at first and then expanding to form a downy mass. These cling ever more 
tentatively until the slightest breeze sets them aloft. Botanists estimate that, under the right conditions, the seeds can travel air currents for nearly 200 miles/300 km! Fireweed is also exceedingly prolific, with a single mature plant producing up to 80,000 seeds in a year. Emptied of their offspring, the spent seed capsules remain as a distinctive wizened frizz until winter.
The plant is a perennial that sprouts each year from rhizomes3Rhizomes are thickened stems that grow along or under the soil surface and bear shoots above and roots below. that spread to form large clumps. Each stem typically grows unbranched and reaches up to 9.00 feet/2.70 meters in height, although they more commonly attain around 5.00 feet/1.50 meters and occasionally branch laterally from the main stem. New leaves are tinged red and spiral around the main stalk on short leaf stems, or, petioles. The lanceolate4Elongated and pointed, or, lance-like leaves are entire5Having untoothed edges or finely toothed with a central midrib from which side veins branch outward and rejoin to form a marginal vein along the leaf edge. The veins are much more prominent on the undersides of the leaves. Smaller leaves continue up the inflorescence as bracts6Bracts are leaves that occur within or just below a flower cluster and often differ in size, form, and sometimes color from ordinary leaves. at the base of each bud. In autumn, the leaves flush to gold, smoldering orange, and deep mahogany. (Like its close relatives in the Epilobium genus, fireweed’s leaves and stems resemble those of young willow trees, earning it the common name “willowherb”, as well as “blooming Sally” from a diminutive of the Latin and Gaelic words for willow, salix and saileach, respectively.)
Fireweed’s long-distance seed dispersal likely contributes to its circumboreal distribution throughout northern Europe, Asia, and North America. Look for it in moist forest clearings, subalpine meadows, and disturbed areas from sea level to subalpine elevations. In North America, it is found across Canada and most of the United States except for parts of the South and Midwest. A pioneer species, fireweed is one of the first plants to spring up after fire, logging, or other ecological disruption, often in great numbers. (Hence another of its common names in the United Kingdom, “bombweed”, as it was quick to colonize craters left from World War II bombings.) Needing full sun to thrive, fireweed is gradually replaced by taller successor plant communities and retreats to its typical habitat in skylit woodland gaps and mountain meadows.
Botanists are divided on whether the proper genus name is Chamaenerion, as it was initially given, or Chamerion, which was later suggested as a shortened version or subgenus. Although Chamaenerion appears to hold the better claim, enough respected sources continue to use Chamerion that both remain legitimate synonyms of the other for the time being.
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