This is a very good and comprehensive companion planting guide from Permaculture Australia. To see/print the thing in a readable format, the PDF address is below. http://www.permaculture.org.au/resources_files/Poster_GDN_Com_Plant.pdf —
Looking to add a perennial garden to your yard? This guide covers all the basics, from planning to planting, along with planting plans for inspiration and case studies of several real-life perennial gardens.