AWARD OF GARDEN MERIT
The Royal Horticultural Society’s AGM award is aimed at helping
gardeners to make informed choices about which of the many plants
available they should buy. 

The AGM is only awarded to plants that are:
• excellent for ordinary garden use
• available
• of good constitution
• essentially stable in form and colour
• reasonably resistant to pests and diseases
• reasonably easy to grow

A hardiness rating is an integral part of the scheme, with the ratings
described as follows.

H1 requires heated glass
H2 requires unheated glass
H3 hardy outside in some regions or particular situations or which, while
usually grown outside in summer, needs frost-free protection in winter
(e.g. dahlias)
H4 hardy throughout the British Isles
H1-2 intermediate between H1 and H2
H2-3 intermediate between H2 and H3
H3-4 intermediate between H3 and H4
H1+3 requiring heated glass; may be grown outside in summer