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About the RHS Award of Garden Merit

RHS Award of Garden Merit

The Award of Garden Merit (AGM) is given by the Royal Horticultural Society (RHS) and helps gardeners make informed choices about plants. This award indicates that the plant is recommended by the RHS.

Who Makes the Award of Garden Merit?

Awards are awarded after a period of trial at an RHS garden and judged by the Society’s Standing and Joint Committees. Committees draw upon the knowledge and experience of a wide range of members, including nurserymen, specialist growers, and well-known horticulturists.

Grading AGM Varieties

There is no grading system within the AGM, and no attempt is made to distinguish the good from the very good. Committees are expected to set a particular standard against which each plant is to be judged: if a plant equals or exceeds the standard, it may be recommended for the award.

No limit has been placed on the number of plants that may hold the award at any one time, but in groups that include many cultivars, standards have to be set especially high if the AGM is to offer helpful guidance to the gardener

Criteria for Making the Award of Garden Merit

The RHS states that for a plant to be awarded the coveted AGM it should comply with the following criteria:

  • Must be of outstanding excellence for ordinary garden decoration or use
  • Must be readily available
  • Must be of good constitution
  • Must not require highly specialist growing conditions or care
  • Must not be particularly susceptible to any pest or disease
  • Must not be subject to an unreasonable degree of reversion in its vegetative or floral characteristics

Hardiness Ratings

In addition, every AGM plant has a hardiness rating. This is intended to serve as a general guide to growing conditions. The hardiness rating is an integral part of the AGM, and should be included in any citation of the award.

Every plant that gets the Award of Garden Merit has a hardiness rating that gives a general guideline to growing conditions.

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

Resources: Royal Horticultural Society

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