Multi-headed Fireweed (Chamerion angustifolium)

Observation by Holly Dean:

This summer I have noticed several fireweed plants on our property in Fairbanks that have multiple flowering heads. On one in particular, I counted 19 flowering heads coming from one stem! I have never seen phenomenon before, is this something new? Is this an adaptation to climate change, or perhaps a response to the overgrowth of invasive vetch?

Matt Carlson, Director for the Alaska Center for Conservation Science, writes:

Those photos look like the primary flowering shoot was damaged in development (pulled off or moose eaten or something). When this happens the hormones coming from the growing tip down the stem that repress lateral bud growth are interrupted and the side branches go wild. This is the same phenomenon when you see “broomed” willows – where moose have eaten the terminal buds and it causes a much bushier growth form.

Comments from LEO Editors:

In August, Mike Brubaker submitted another observation of fireweed with multiple blooming heads. Through conversation with other LEO staff, we realized that this was occurring in other residential areas in Anchorage and Wasilla. Considering how much we enjoy fireweed honey, we can understand why a moose would want to sample the same flowers!