In article ,
Janet wrote:

It's also unclear how many of the claims of ecological harm are
actually justified. Japanese knotweed is, in many places, and
R. ponticum can be, but I have never seen Himalayan balsam form
monocultures. My suspicion is that even R. ponticum is only a
major ecological problem in a few areas - though it may be a
bloody nuisance to humans more widely, just like nettles, bindweed
and so on.

It certainly is an ecological problem in west Scotland; in woodland
it smothers natural regeneration of native plants, particularly worrying
as older trees die naturally.

I accept that it can be - what I am saying is that the frequent
claims that it usually (or even always) is are almost always made
without any attempt at providing justification. Inter alia, it
is an undershrub in most climax woodland, and I have have both
seen it NOT smothering regeneration and seen no data that it does
under such circumstances.

It's also a host plant of phytopthera
as older trees die naturally. It's also a host plant of phytopthera
kernoviae and ramorum

http://ucanr.org/sites/sod5/files/147415.pdf

As are many plants. It's unclear to what extent that is demonisation.

I have looked at several papers describing its harmfulness, but all
of the decent ones have pointed out that quite a few conditions are
needed for that, and several describing its distribution. But I
have never seen one analysing how widely it is an ecological problem.
I have seen it being so, myself, but only on a small scale - however,
that is also true for Japanese knotweed.

And, as I say, as far as I can discover, several plants (mainly
Himalayan balsam and bracken, but also Oxford ragwort, Buddleia
davidii and others) have be claimed to be ecological problems, but
without any attempt at providing evidence and (in my experience)
without justification. Yes, they can be bloody nuisances to humans,
but that is not the same.


Regards,
Nick Maclaren.