I went for a run the other day and nearly got thwacked to bits. Nothing terribly serious, mind you, but a good reminder of the exuberant abundance of one of the region’s, and, in fact, the northern hemisphere’s most prolific plants: fireweed (Chamaenerion angustifolium). They grow widely in our front yard, throughout the Cascades, circumboreally, and up to 16,000 feet in elevation in the Himalayas. Fireweed also thrives in disturbed habitat, such as adjacent to trails in lesser visited Seattle parks, which is where I encountered my floral attackers. And, of course, as the name implies, they quickly move into fire-burned areas.
Fortunately, few of the thwacker plants had ripe seeds. Otherwise, I would have looked as if I had just escaped a pillow fight with pillows stuffed with dog hair from my pal Scott’s Great Pyrenees dogs. Each fireweed plant can produce 80,000 tufted seeds. All it takes to crack open the several-inch long, spaghetti-esque seed pods is a light thump. I know this from the dozens of fireweed plants covering our front yard. I regularly pull up the mature stalks at the end of summer, carry them to our backyard, and drop them en masse on the ground. When I do so, the pods burst open and let loose the tightly packed, lanuginous seeds, which take to the wind and waft into the world, and into the world quite a distance, or so say researchers.
In a thrilling and exacting study, two Swedish botanists married advanced mathematics with a complex meteorological analysis to determine how far a typical fireweed seed might fly. Shockingly, no one had ever studied this facet of the life of fireweed until the 1987 study. The scientists obtained their raw data from suction traps (normally used for insects but also adaptable, when the need is great enough, for seeds) attached to a several-hundred-foot tall TV tower.
The Scandinavian duo found that fireweed seeds regularly reach altitudes of more than 320 feet above the ground when dispersing. Those airy seeds, because of their fibrous nature, will then take 25 minutes to fall to the ground in still air. Assuming a light wind (9 mph), one seed can travel nine miles in an hour! The pair then calculated, and here’s where it gets rather exciting, that since it was not “uncommon for seeds to be aloft for 10 hours during a summer day,” seeds could disperse nearly 200 miles. (I like to think that the gazillions of seeds that have dispersed from our backyard have found nice homes somewhere, perhaps as far north as Canada.)
This superpower of riding the open skies has resulted in fireweed colonizing two notable areas. During World War II, fireweed, or as the British call the plant rosebay willow herb, was the “pioneer colonist of the bombed sites” wrote R.S.R. Fitter in London’s Natural History. He estimated that the plants grew in 90% of London’s WWII ruins, which resulted in another common name: bombweed.
Closer to home, fireweed was one of the first plants to return to Mount St. Helens after the 1980 eruption. Botanists described them as parachutists, and observed how fireweed was always one of the top five species collected at sites around the mountain in the first few post-eruption years. After settling onto areas such as the Pumice Plain, fireweeds turned on their other superpower, vegetative reproduction by rhizomes. (Ecologists call this type of plant a geophyte, or a plant that has an underground storage organ, such as a potato.) Spreading widely and quickly in such a manner allowed fireweed to form beautiful stands of tall, green-stemmed, linear-leaved, purple-flowered plants.
Plants such as fireweed play a critical ecosystem role. By colonizing disturbed habitat, they help create the conditions for other life and lives to move in, repopulate, and reinvigorate, ultimately leading to a complex community of plants and animals. But as fireweed did in London, such plants can also do the same with our spirit, as they brighten landscapes that appear beaten and defeated. Perhaps we should relabel the plants Purple Flowers of Hope!
Word of the Week - Lanuginous - The OED defines this fine word as covered with soft or downy hair, an apt description of fireweed seeds. Its use in English comes from the Latin lānuginōsus, which derives from the root word lana, or wool, as in lanolin.
Word of the Week 2 - Chamaenerion - Depending upon the botany guide you read, you may see fireweed listed in one of three genera: Chamaenerion, Epilobium, or Chamerion. The variety of names has to do, in part, with egos, and first usage; in scientific naming, the first name used rules all others. For many decades and in many many publications, Epilobium merited more use but recently Chamaenerion has come back into preference. Chamerion, meanwhile, is an upstart, a name first proposed in 1817 by the supremely arrogant botanist Constantine Samuel Rafinesque. “I can boast at least of some accuracy and taste in Nomenclature: I frame none but good or meaning Names, none of mine are bad…” His main reason for his new name was that the previous one had too many syllables so he shortened it. Unfortunately, the genus I like did not prevail; in 1916, botanist Joel Lunell proposed Pyrogennema, from the Greek for “fire that which is begotten.”
August 12, 2025 – Stories in Stone – 6:00 P.M. – I’ll be leading a walk for Birds Connect Seattle looking at the geology of downtown buildings. Registration.
