Every year, the RHS conducts trials to see which plants deserve the RHS Award of Garden Merit (AGM). At our September ‘22 meeting Fergus Garrett told us about the RHS plant trials, in order to help us to find out about the best of new plants. Particularly about tomatoes with heritage plants being better ‘doers’ than the F1 varieties. Here are the trials taking place this year and beyond, on show to garden visitors.

Awards of Garden Merit (AGM) are normally assigned after a physical assessment, judged by a panel of experts made up of specialist growers and renowned horticulturists. Slower-growing plants, such as some trees and shrubs, are judged by an expert panel via Roundtable discussion. Every year around 30 trials are held at venues throughout the UK, including at RHS Gardens.

Once an RHS Plant Trial has finished, we share the findings to help you choose the best plants for your garden. 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. Click here for further information about trials results.

Click here to get to the current trials pages on the RHS website. Below is the list of the Trials Garden, RHS Garden Wisley

  • Apiaceae family: 2021–23

  • Dahlia: 2021–23

  • Fritillaria imperialis (crown imperial): 2021–22

  • Helleborus: 2021–24

  • Hyacinthus orientalis (hyacinth): 2021–22

  • Lathyrus odoratus (sweet pea): 2021–23

  • Narcissus, shorter-flowering: 2021–23

  • Oregano and marjoram: 2022–23

  • Rosa, red-flowered: 2021–24

  • Salvia, hardy: 2022–24

  • Tomatoes: 2022

  • Tulipa, early flowering: 2021–22

Trials at other RHS Gardens

  • Celeriac: 2022, RHS Garden Bridgewater, Salford (and celery trial) RHS Garden Rosemoor, Devon

  • Cornus sanguinea and C. sibirica: 2021–23, RHS Garden Hyde Hall, Essex

  • Dianthus, border carnation: 2021–24, Bridgewater

  • Garlic: 2022, Rosemoor / Bridgewater

  • Geum: 2019–22, RHS Garden Harlow Carr, North Yorkshire

  • Helenium: 2022–25, Bridgewater

  • Hydrangea paniculata: 2021–24, Bridgewater

  • Melons: 2022, Rosemoor / Bridgewater

  • Primula: 2021–23, Bridgewater

  • Spring cabbage: 2021–22, Bridgewater / Rosemoor

  • Veronica (hebe): 2021–24, Harlow Carr / Wisley

Off-site trials

  • Aeonium: 2022–24, Minack Theatre, Cornwall (also Wisley)

  • Chaenomeles: 2021–24, Witch Hazel Nursery, Kent

  • Erica, winter-flowering: 2015–23, Threave Garden & Estate, Dumfries & Galloway

  • Hemerocallis: 2018–23, Sissinghurst, Kent and Floors Castle, Kelso

  • Mahonia: 2021–25, Sir Harold Hillier Gardens, Hampshire

  • Spiraea: 2019–23, East Ruston Old Vicarage Garden, Norfolk