The hackberry is similar to an elm, but it has a berry while the elm does not. These pea-sized dark purple berries provide food for songbirds. Frequently buds on the hackberry are deformed causing twigs to grow in tangled bunches. These are called witches' brooms. They don't hurt the tree, however, they do keep it from being pretty. Like the elm, the hackberry leaves curve gracefully to one side. These leaves are often deformed by tiny, jumping lice which form warty growths on the leaves. In the Bluegrass, the hackberry is an important source of wood for tobacco sticks.