Iris lazica
Peter Taggart (Thu, 09 Feb 2012 10:04:56 PST)

Derbyshire last winter, the diesel waxed in fuel lines in Belper and
minimum temperatures read -20 C nightly in Darley Abbey, Derby.
I am quite sure that the "High Peak" in Derbyshire was several degrees
colder due to altitude, (Buxton area). My sister gardens there and grows
both Iris lazica and unguicularis. It was a very unusual winter for Britain
and the coldest of my life time. Most records seem to be written for the
south of Britain which is rarely as cold, or for as long.
When Britain gets clear skys and air from the north east, rather than from
the Atlantic, we can be reminded of our latitude.

Peter, where in the UK are temperatures below 0F (minus 18 C) experienced?