One kind of plant that has purple berries is the pokeweed. This weed can be found growing along roadsides, in clearings and in open woods from Canada down to New England, south to Florida and west to Texas and Mexico.
The pokeweed is a perennial that can grow to 10 feet high. It bears drooping clusters of purple berries after clusters of small, white flowers. The roots look very much like potatoes, but both the root and the berries are poisonous to humans. The stem and mature leaves are also poisonous, but the young and tender shoots can be eaten as greens.