For the record....the USDA zonal chart was designed for use in the USA. It
is but one of a number of "tools" that keen gardeners use.......an extremely
useful tool I might add.....of course, like many things, it is by no means
foolproof. It does serve the purpose of being an indicator of the cold
hardiness of perennials and shrubs. It does not discuss sun or shade, dry
or wet nor the pH requirements etc. etc.

I would never think of planting a valuable planting without first consulting
its USDA hardiness zone, unless I was considering growing in the
conservatory.

HW.