In message , writes
In article ,
Janet wrote:

I've known R.ponticum take -24 C (in Scotland) without a blink. I've
also known well established plants blown out of the ground in windspeeds
over 100 mph.. wind exposure is probably the greatest inhibition it
faces in Scotland :-)

How deeply did the ground freeze? That is often a more important
factor than the low temperature.

Our underground water supply pipe on the moor was frozen for 10 days
:-(. It's supposed to be buried 3 ft deep but probably shallower in some
rocky sections. Trees and daffodils survived.

That's cold.

A farm neighbour had a large deciduous woodland heavily infested with
Rp which he was trying to eliminate, but that exceptionally cold spell
did not affect it at all.

The hardy forms are much hardier than I had realised, then.

It seems that the hardier forms of R. ponticum are actually a hybrid
with R. catawbiense and that it is often fairly tender:


http://www2.warwick.ac.uk/fac/sci/li...-schmutz/rp_hi
story_eh2006.pdf

Interesting article, thanks. To think they actually bred it to be
hardier :-)

Yup. Much of what it said was news to me. I think that there are
a lot of poorly-studied oddities about the adaptation of plants
and animals to the UK. We know that there are several plants that
have hybridised (or been bred) and have naturalised only in that
form, but the indication of that paper is that this isn't a simple
cross. And, of course, there is the question of why and how rabbits
changed from an animal that needed help to survive the winter to
one which most definitely doesn't!

People are now beginning to take up the name Rhododendron x
superponticum for the wild British rhododendrons.

URL:http://www.rhs.org.uk/Plants/RHS-Pub.../Hanburyana/Ha
nburyan-issues/Volume-5--June-2011/Naturalised-rhododendrons

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.


Regards,
Nick Maclaren.

--
Stewart Robert Hinsley