PLANT HARDINESS ZONES UK AND USA

I always tend to get confused when I have my eye on a certain plant and the label tells me it needs a certain condition, partial shade, a hardiness level or zone of whatever, and I am left trying to work out if my growing conditions fit the bill.  I did a bit of research regarding hardiness (and understanding light and shade in gardening):

PLANT HARDINESS, RATINGS AND ZONES



Plant hardiness is treated differently in the United States of America to the United Kingdom.  The USA which is many times larger than the UK, as we all know, is divided into United States Department of Agriculture (USDA) hardiness zones from 0 to 13b.  It's all far too complicated for me to go into but here are a few useful links for you:



USDA - Plant Hardiness Zone webpage

USDA - Agricultural Research Service interactive map

UK - PlantMaps.Com - Plant hardiness interactive map - Fahrenheit

UK - PlantMaps.Com - Plant hardiness interactive map - Celsius

UK - Royal Horticultural Society New (2012) Plant Hardiness Ratings

HARDINESS
U.K.		USA
Rating	Centigrade	Zone
H1a	Above 15	13
H1b	10 to 15	12
H1c	5 to 10	11
H2	1 to 5	10b
H3	1 to -5	9
H4	-5 to -10	8b/9a
H5	-10 to -15	7b/8a
H6	-15 to -20	6b/7a
H7	Below -20	6a/1