In message , kay
writes

Bob Hobden;896506 Wrote:
"Stewart Robert Hinsley" wrote-
Presumably another garden escape, seen growing in a street in front of
an electricity substation.

http://tinyurl.com/36bq8bf
http://tinyurl.com/39pwyvb-

Looks like square stems so a member of the mint family, like Agastache
urticifolia. Giant hyssop, perhaps.

--


Is it not Purple Loosestrife?

I think you've got it. (Thanks.) It's much smaller than the general run
of Lythrum salicaria, but I did suspect it of being a depauperate plant
of some species.

I'm used to picking purple loosestrife out as "tall purple-flowered
perennial, not rosebay or great willowherb, growing next to water",
which doesn't work for a small perennial growing in a pavement crack.
--
Stewart Robert Hinsley