James A. Duke 
Handbook of Edible Weeds [PDF ebook] 
Herbal Reference Library

Handbook of Edible Weeds contains detailed descriptions and illustrations of 100 edible weeds, representing 100 genera of higher plant species. Some of the species are strictly American, but many are cosmopolitan weeds. Each account includes common names recognized by the Weed Science Society of America, standard Latin scientific names, uses, and distribution (geographic and ecological). Cautionary notes are included regarding the potential allergenic or other harmful properties of many of the weeds.