Monty Don and the team celebrate the changing seasons and the beauty of the gardening year in all its glory. Colour and fragrance are even more valuable in winter, when the skies are grey. Carol Klein visits a garden in Somerset filled with some of the best shrubs that offer both flowers and scent in the colder months. Nick Bailey explores a garden that looks beautifully wild but is meticulously designed with layers of planting to create a naturalistic style that is great for biodiversity. Adam Frost is at Borde Hill Gardens in West Sussex, discovering how their collection of some of the rarest trees in the country could provide the key to what we grow in the future. There's also a visit to an orchard in Shropshire to get a masterclass in winter pruning for healthy and productive trees, and some keen plot holders on an allotment site in Birmingham, who explain just how much their patch means to them. Plus a chance to see what viewers have been getting up to in their gardens.