Re: New Potential Weed

One of the most striking things to me about discussions of exotic plant
invasions is just how localized and specific the problems are. What is a
terrible weed one place is not in another despite superficially similar
conditions of climate etc. Why does a particular plant become a bully to
the exclusion of all others in one area, not volunteer at all in another
and simply become another integrated member of the plant community in
yet another? There must be important clues to the distribution of plants
and just what is involved in the assembling of plant communities in
these patterns somewhere.

If we could begin to figure this stuff out it would certainly make
creating self-sustaining landscapes a lot more successful, something I
think a lot of us would like to move toward.  I, for one, am not willing
to take my place back to its wild-type vegetation (even if it were
possible--which it is not with starthistle and all now) with only
natural rainfall, yet I am not interested in being the person who
inflicts the next starthistle on California either.

Unfortunately, the experience of people in even seemingly similar
Mediterranean-type climates is not always a good predictor.  For
example, Gaura lindheimeri has never even set a seed, much less gone
invasive here. I've heard that Pinus radiata is invading the fynbos in
South Africa, yet it is barely hanging on in it's native range and we
cannot even grow it successfully here in the central valley.  

Why have chicory and moth mullein (sorry, I don't have their real names
at my fingertips) become integrated into the 'new' California annual
grassland community (at least here in the Sacramento Valley) while
starthistle is spreading its vicious monoculture like wildfire through
the same community?

Is there any alternative other than planting and waiting to see? Should
I forgo a beautiful plant because it has become invasive somewhere else?
How similar must the conditions be, and what components of the
conditions are most important, for a plant to behave in a similar
bullying fashion?

This leaves me in somewhat of a quandary, since one of my greatest
delights is acquiring new kinds of plants and watching them grow
successfully.  A 'topical' topic for me.

Gary Matson, in Far Northern California
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