In a special programme which comes from all four of the Royal Horticultural Society gardens, the Gardeners' World team are out on the road exploring how each location's differing climate affects the plants they grow and getting plenty of gardening tips along the way. Carol Klein introduces the programme from Wisley in Surrey, one of the country's southern 'hot spots'. She finds out how plants are assessed in their trial beds and how that information is useful to all gardeners. In the northernmost garden at Harlow Carr in Yorkshire, where the winters can be quite harsh, Joe Swift gets plenty of timely propagating tips. Rachel de Thame explores the gardens at Hyde Hall in Essex, the driest county, and discovers plants which thrive with minimal rainfall. By contrast, in the west, where the rainfall is high, Monty Don visits Rosemoor in Devon and finds plenty of inspiring planting combinations in their colourful 'hot borders'.