The Award of Garden Merit (AGM) is a long-established annual award for plants by the British Royal Horticultural Society (RHS). It is based on assessment of the plants' performance under UK growing conditions and helps gardeners choose the very best all round varieties.
Awards are only made after assessment by an RHS forum of experts, drawing upon the experience of nurserymen, specialist growers and well-known horticulturists. The trials and assessments usually take place at one of the RHS Gardens but can also take place at an RHS partner gardens, National Trust gardens or commercial nurseries. They look at the following criteria.
Excellent for ordinary use in appropriate conditions Good constitution Essentially stable in form and colour Reasonably resistant to pests and diseases