Perennial Vegetables

Source: Wikipedia - Markus Leupold-Löwenthal

Anni Kelsey gave a very interesting and informative talk on her experiences growing perennial vegetables which included oca (shown above). Check her blog for more info.
Suppliers of perennial vegetable seeds, plants and tubers include:

Edulis

Agroforestry Research Trust

 The Real Seed Catalogue

Chiltern Seeds

 Yakon.co.uk