RHS Hardiness Ratings

The RHS have their own system of H (Hardiness) ratings that are universally used throughout the UK to indicate hardiness. To assist you with your selection we show these ratings and also indicate the lowest temperatures that our plants will survive in.

H1 = plants requiring heated glass in the British Isles

H2 = plants requiring unheated glass in the British Isles

H3 = plants hardy outside in some regions of the British Isles or in particular situations, or which, while usually grown outside in summer, need frost-free protection in winter

H4 = plants hardy throughout the British Isles

H1-2, H2-3, H3-4 = plants intermediate between the two ratings given

Please note that the RHS ratings are fairly broad and other factors such as site selection, drainage and micro climates may need to be considered.