Another small tree, wild plum are often noticeable for the large, black cankers that grow on their stems, the result of the black knot fungi. Plum will often form small, many stemmed thickets. They have thorns and might be mistaken as a hawthorn, although the leaves have a different shape, and the plums are much like the small, yellow plums which are cultivated, and are equally good to eat. The flowers and fruits are borne in small clusters along branches.