With spring gaining momentum, Adam Frost gets to work on his veg plot and plants his first lot of potatoes. He introduces roses to his borders, and in a quest to increase biodiversity, has a radical plan for his lawn. Joe Swift meets a garden designer who, facing the challenge of two awkward, adjoining plots, transformed them into wonderful, cohesive spaces. And Rekha Mistry demonstrates how to grow the perfect onion from seed and has a go at growing cotton.