• AGM plants

    AGM plants have been through a rigorous trial and assessment programme. They are:

    • Excellent for ordinary use in appropriate conditions
    • Available to buy
    • Of good constitution
    • Essentially stable in form & colour
    • Reasonably resistant to pests & diseases
Our plant trials are a unique resource, as they're free from commercial interest and are aimed at helping home gardeners make the most informed choices possible about the plants they buy. Information from these trials is available in several formats:
 
  1. RHS Grower Guides aim to interpret the trial results in a handy, accessible format and include cultivation advice as well as a supplier list.
  2. Trial Reports are technical documents giving details of what was on trial, who supplied it and and how the plants performed.
  3. Trial Bulletins are documents aimed at interpreting the results of the trials for gardeners. They have been discontinued and have been superseded by RHS Grower Guides.

RHS Grower Guides

  


We are currently producing a series of RHS Grower Guides. Each one focuses on a particular genus, and contains a wealth of information to help you select the best varieties for your garden. Click the covers in the bookcase above to view or download individual guides.

The guides also contain growing information, which planting partners work best and how to combat common pests and diseases. The guides are produced on the back of recent RHS plant trials, and offer useful information and advice from the experts on the cultivars that performed well enough to achieve an Award of Garden Merit (AGM).


Trial reports

To access trials reports please go to the RHS Plant Trials Database


Trial bulletins

Although they are now being superseded by Grower Guides, plant trial bulletins are still available to download (see list below). Please be aware that they may not give the most up-to-date information on AGMs – please consult our AGM lists for current awards.

Printed bulletins of AGM plant groups

Bearded irises
The bulletin gives details of 90 AGM award-winning bearded irises.

Begonia rex Cultorum Group
This bulletin follows the completion of a trial of 87 cultivars at RHS Garden Wisley.

Canna
This bulletin gives details of 22 AGM award-winning cannas.

Caryopteris
This bulletin gives details on all AGM cultivars and information on their cultivation and origins.

Chilli peppers
This bulletin follows the trial of chilli peppers at RHS Garden Wisley and East Ruston Old Vicarage.

Clematis alpina and Clematis macropetala
This bulletin follows the trial of Clematis alpina and Clematis macropetala at RHS Garden Wisley.

Delphinium
This bulletin contains details of the 40 AGM Delphinium cultivars after trials at RHS Garden Wisley.

Hardy geraniums - stage 1
This bulletin contains details of six AGM hardy geraniums and the four AGMs that were reconfirmed.

Hardy geraniums - stage 2
This bulletin contains details of 10 AGM hardy geraniums and the three AGMs that were reconfirmed.

Hardy geraniums - stage 3
Stage 3 features plants with specialised cultivation, including geraniums suitable for rock gardens.

Hardy lavender
The 18 AGM winners are described in full along with details of all plants submitted for trial.

Herbaceous sedums
This bulletin follows the completion of a trial of 90 sedums at RHS Garden Wisley.

Hyacinthaceae - little blue bulbs
This bulletin contains details of the small members of the Hyacinthaceae family in the trial.

Hydrangea paniculata
This bulletin follows the completion of the trial of Hydrangea paniculata at RHS Garden Wisley.

Miscanthus
This bulletin covers 60 different Miscanthus with more detail on 16 cultivars of Miscanthus sinensis.

Open-centred dahlias
There are 13 different classification groups for dahlias - only those with open centres (single-flowered, collerette, miscellaneous and single orchid) are featured in this publication.

Perennial yellow daisies
This bulletin contains details of 36 perennial yellow daisy cultivars (including Coreopsis, Helenium, Helianthus, Heliopsis and Rudbeckia)

Perovskia
This bulletin follows the trial of 11 Perovskia at RHS Garden Wisley. One aim of this small trial was to sort out the correct identity of individual cultivars.

Pittosporum tenuifolium plant assessment
This plant assessment contains details of the AGM cultivars together with a further 42 cultivars.

Rhododendron yakushimanum
This bulletin contains details of the recent long-term trial and full information on the 28 entries.

Runner beans
This bulletin follows the completion of a trial of 48 runner beans at RHS Garden Wisley.

Salad potatoes
This bulletin contains details of the 10 salad potato cultivars that have been awarded an AGM.

Shrubby Potentilla
A report on the RHS trial 1996–2001 with details of the trial objectives, awards recommended and descriptions of almost 100 cultivars.

Silver saxifrages
This bulletin contains details of the 15 silver saxifrages that have been awarded an AGM.

Spiraea japonica with coloured leaves
Spiraea japonica cultivars with coloured leaves are useful garden shrubs; see the 18 trialled.

Sweet peppers
This bulletin provides details of the trial plus the 16 cultivars that received an AGM.


The Garden Podcast

A peek behind the scenes at The Garden magazine with exclusive interviews, gardening advice and more.

Listen now

Get involved

The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.