Every year, the RHS conducts trials to see which plants deserve the RHS Award of Garden Merit (AGM). Here are the trials taking place this year and beyond that are 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.
Trials Garden, RHS Garden Wisley, Surrey
- Aeonium: 2023–2025, RHS Garden Wisley, Surrey / Minack Theatre, Cornwall
- Baptisia: 2024–2026
- Centaurea: 2024–2026
- Dahlia: 2023–2024
- Delphinium (seed strains): 2023–2025
- Diascia (annual): 2024
- Gladiolus: 2024–2025
- Helianthemum: 2024 –2026
- Lathyrus (sweet peas): AGM display
- Lupins: 2024–2026
- Muscari (in containers): 2024
- Nandina: 2024 –2026
- Narcissus (shorter types): AGM display
- Rosa (red-flowered): 2021–2024
- Salvia (hardy): 2022–2024
- Tulipa (fringed and lily flowered): 2024
- Viola (overwintering): 2024
- Phalaenopsis (Orchid House): 2024–2025
Trials at other RHS Gardens
- Aubretia: 2024–2026, RHS Garden Hyde Hall, Essex
- Camassia: 2024–2025, RHS Garden Bridgewater, Salford
- Helenium: 2022–2025, RHS Garden Bridgewater, Salford
- Hydrangea paniculata: 2021–2024, RHS Garden Bridgewater, Salford
- Sunflowers (fleuroselect display): 2024, RHS Garden Hyde Hall, Essex
- Gooseberries: 2023–2026, RHS Garden Bridgewater, Salford
Vegetables:
- Broccoli (purple sprouting), Cabbage (autumn/winter storing), Tomatoes (beefsteak): 2024, RHS Garden Bridgewater, Salford
- Cabbage (autumn/winter storing), Peas (mangetout and sugar snap), Tomatoes (beefsteak): 2024, RHS Garden Rosemoor, Devon
- Broccoli (purple sprouting), Potatoes, Tomatoes (beefsteak) (behind the scenes): 2024, RHS Garden Wisley, Surrey
Off-site trials
- Aruncus: 2024 –2026, Royal Botanic Garden Edinburgh
- Chaenomeles: 2022–2025, Witch Hazel Nursery, Kent (open days only)
- Filipendula: 2023–2025, Royal Botanic Garden Edinburgh
- Hedychium: 2024–2025, East Ruston Old Vicarage Garden, Norfolk and Floors Castle, Kelso
- Mahonia: 2023–2025, Sir Harold Hillier Gardens, Hampshire (behind the scenes)
- Tillandsia: 2023–2025, Walton Hall and Gardens, Warrington
For more information on our trials please email [email protected].
Useful links
