Topic summary
USDA zones
Extracted from the Wikipedia article Hardiness zone.
Britain and Ireland
USDA zones do not work particularly well in Ireland and Great Britain as they are designed for continental climates and subtropical climates. The high latitude, weaker solar intensity, and cooler summers must be considered when comparing to US equivalent. New growth may be insufficient or fail to harden off affecting winter survival in the shorter and much cooler summers of Ireland and Britain.