The late plantsman Alan Bloom was the catalyst behind the formation of the Hardy Plant Society more than 50 years ago. The buoyant 11,000-strong membership consists of serious yet sociable gardeners and you're bound to be close to one of the 40 or so local groups. There are also six specialist groups covering pulmonarias, hardy geraniums, peonies, variegated plants, ranunculaceae and half-hardies. This network of groups is the strength behind the society's success; it exhibits at Chelsea and leading shows. The annual HPS seed swap features nearly 2,000 varieties of annuals, biennials and perennials and members receive 20 free packets for £5. If you donate seeds you can ask for 10 more packets.

Membership: Single; joint £15 (01386 710317; www.hardy-plant.org.uk)