In the last of four special programmes, Frances Tophill is at Wildside Garden in Devon with inspiration to make our winter gardens sparkle and jobs to get them ready for next spring. Nick Bailey visits a plot in Bedfordshire that blends soft grasses with textural trees and crisp topiary to create a space full of winter interest. Advolly Richmond reveals the history of greenhouses, along with the enormous challenges involved in engineering those early designs. And Adam Frost gets stuck into some winter jobs, including planting up a container for seasonal interest