Documentary series going behind the scenes at The Royal Horticultural Society. This time we see eco-friendly gardening in practice at Harlow Carr, the society's most northerly garden. The garden is prone to flooding and this summer, curator Matthew Wilson finds an elegant yet high-tech solution using dry stone walls. Also, the students at Wisley design and dig their allotments and children in Wakefield benefit from an RHS scheme encouraging children to grow their own vegetables.