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.

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...ory_eh2006.pdf


Regards,
Nick Maclaren.