There will be 28 trials this year, of which 13 will be new plants, and 38 trials in 2013, of which 20 will be new.
The trials will cover fruiting plants such as blackberries and hybrid berries and flowering plants such as penstemon, Digitalis and clematis. Vegetables to be assessed include sprouting broccoli and runner beans.
New trials in 2012 include basil, cos and gem lettuce, tall bearded iris and Mexican salvias. Plants for 2013 will include Solenostemon, astrantia, alpine dianthus and large, late-flowering clematis.
"The RHS is focused on helping all gardeners make informed decisions about their plants and the RHS plant trials are an important tool towards this aim," said RHS director of horticulture Jim Gardiner.
"Our trials programme over the next two years is really exciting and extensive and includes plants that are increasing in popularity such as hybrid berries."
New panel members, who will help judge the trials, include Inner Temple Gardens head gardener Andrea Brunsendorf, plantsman and TV presenter Toby Buckland, Hillier Nurseries director Kevin Hobbs and garden designer Rachel Prior.
The AGM is awarded to plants that are excellent for ordinary use in appropriate conditions, readily available, of good constitution, essentially stable in colour and form and reasonably resistant to pests and diseases.