As part of his planning for summer, Monty begins to sow annual climbers and gets started on tidying and mulching his borders. In the last of Joe Swift's series on trees, he learns how and when to prune them, and why. We meet clematis enthusiast Mike Brown, whose collection fills his garden with colour all summer long, and amongst the brutalist architecture of London's Barbican, Nick Bailey, head gardener of the Chelsea Physic Garden, discovers a hidden tropical oasis.