Adam Frost and the team celebrate the joy that the gardening year brings with a selection of brand new stories.Nick Bailey visits the winter garden at Sir Harold Hillier Gardens in Hampshire; Frances Tophill discovers the largest cultivated collection of Mediterranean plants in the great glasshouse at the National Botanic Garden of Wales; and Carol Klein immerses herself in the exuberance of high summer at Kelmarsh Hall Gardens in Northamptonshire.Meanwhile, Arit Anderson meets a couple in the Pennines who have created a garden on the most challenging of plots, and Rachel de Thame shines a light on a plant that dazzles in the depths of winter – witch hazel.We visit an artist in County Wicklow, Ireland, who curates his garden like a living canvas, and we meet a passionate gardener in Wiltshire who has taken her love of tulips to a whole new level.There is also a chance to see what viewers have been getting up to in their own gardens.