Here are some reliable links from university cooperative extensions and other sources around the country.
As the plants will vary regionally it is important to seek out information pertaining to your specific region. REMEMBER: some plants are toxic at various levels of ingestion…single ingestion or cumulative. Always use caution when identifying and using wild plants and, of course, NEVER eat any plant that may have been sprayed with pesticide.
“The prime directive in foraging for wild plants for consumption is simple, yet its violation has led to illness and even fatalities. You must never consume any part of any plant whose identity is questionable. There are a number of plants whose look-alikes are toxic and whose identity must carefully be ascertained before they are used. Certain parts of some edible plants may be poisonous. Some plants are edible when young but become toxic later on. Some plants are edible during certain seasons but toxic during others. ” Familiarizing Students with some Edible & Poisonous Wild Plants, Barry s. Kendler, Dominick J. Pirone, Manhattan College, Bronx, NY, · The American Biology Teacher Vol. 51, No. 8 (Nov. – Dec., 1989), pp. 463-471 Published by: University of California Press.