Buckthorn is a tall, tree-like shrub with dark green leaves marked by prominent veins that cling to the branches long after a frost, clusters of black, pea-sized berries that appear in fall and remain long after other fruits have dropped, and spine-tipped branches that give it its name; its berries are a favorite of many birds. Along the trail, catnip can be recognized by its square stem, arrow-shaped leaves, and minty aroma. Early settlers made tea from catnip leaves to relieve colic in infants, and it was also used to induce sweating to cure colds. It is also well known for its aromatic attraction to cats.