That was a good list, Don, with good information; thanks. I would add
PURPLE LOOSESTRIFE to the list without hesitation, as it doesn't seem to do
much good for any wildlife and renders a lot of harm by choking out other
more productive marsh vegetation (not to mention eliminating shorebirds
from Montlake Fill, for which it has my personal animosity--but then again,
the people who manage the fill could have managed to eliminate the
loosestrife if they were so inclined).

It's clear that there are hundreds of weedy species that effect relatively
minor changes on ecosystems, but the ones named have the unpleasant
propensity to take over large stretches of (often disturbed) habitat by
successfully outcompeting native and other weedy species, and, for the most
part, they don't have much value to wildlife. Himalayan blackberry
probably is an exception to this, as it furnishes habitat for a lot of
thicket-inhabiting small birds and mammals, and the fruits are eaten by
quite a few species. It's more of a bother to humans than are some of the
others; EURASIAN WATERMILFOIL is a tremendous bother to humans but is used
by a lot of waterfowl; where it gets extremely dense it does choke out
other aquatic vegetation and open-water species of fish and birds.

We definitely should distinguish weeds that are damaging to natural
ecosystems from weeds that are inconveniencing to us. I think bracken
would only fit in the latter category, if at all. As would Russian
thistle, Canada and bull thistles, and some other species. At least we
don't have pernicious TREES, as do many areas of the tropics.

Dennis Paulson, Director phone: (206) 756-3798
Slater Museum of Natural History fax: (206) 756-3352
University of Puget Sound e-mail: dpaulson at ups.edu
Tacoma, WA 98416