In article ,
Brian Robertson writes:
|
| If they are growing thickly enough, I suspect that any of these plants
| would reduce diversity in a given area. Knotweed is, indeed, the worst
| offender though. When it falls back in the winter it leaves a barren
| wasteland behind it.

That is dubious for the others, because they rarely grow thickly enough
to prevent all other plants growing underneath or through them.

| Of course the real danger with Hogweed lies in what its sap does.

Not as much as the hysterics imply. It's little worse than many other
garden plants, which don't attract the same hysteria.

| What upset me about these particular infestations is that they are small
| patches and presumably new, which leaves me wondering (Fearing) what
| that same river bank will look like in 5 or 10 years time. The other
| side of the river is a jungle of knot weed.

I have observed patches of both hogweed and Himalayan balsam over
decades; they rarely expand aggressively and exclusively.


Britain has a very competitive flora, because it is almost entirely
comprised of plants that have invaded or been introduced in the past
11,000 years, and so is at little risk from other introductions. I
can think of a mere handful of plants (native OR introduced) that
form exclusive ecologies except in very unusual circumstances or with
ongoing human help.

Even the most notorious ones (Rhododendron ponticum and Japanese
knotweed) need fairly specific conditions to become exclusive. Are
there any others that reach even that level? I can't think of any,
offhand. Even natural lime or oak woods were/are rarely pure.

Now is the time to quote Douglas Adams ....


Regards,
Nick Maclaren.