Poison ivy will always have leaves of three, as the popular phrase goes. However some plants, like the Jack-in-the-pulpit and blackberry plants (pictured above, left) also have three leaves. As a primer, Sachs ensures that poison ivy should never have thorns and that its leaves should not be hairy. Its important to note that blackberry leaves have serrated fine edges, similar to a wood saw, while poison ivy leaves may just have notched edges.
(Text by Chris Brook / Boston.com Correspondent / Photo courtesy of www.poison-ivy.org)