Smilax rotundifolia

Smilax rotundifolia, also known as roundleaf greenbrier or common greenbrier, or bamboo vine in parts of the South,is a woody vine native to the southeastern and eastern United States and eastern Canada. It is a common and conspicuous part of the natural forest ecosystems in much of its native range. The leaves are glossy green, petioled, alternate, and circular to heart-shaped. They are generally 5–13 cm long. Common greenbrier climbs other plants using green tendrils growing out of the petioles. The stems are rounded and green and are armed with sharp thorns. The flowers are greenish white, and are produced from April to August. The fruit is a bluish black berry that ripens in September....read more on Wikipedia.