Tour Stop 14: Hackberry Trees
This tree with the unusual, warty bark is a hackberry tree. The warts on the bark are not signs of disease. Rather, they are part of the normal appearance of these trees and may provide some protection for the thin, fragile bark.
The hackberry is a relative of the elm. It grows rapidly under a variety of conditions, eventually reaching 60-70 feet.
The hackberry provides food for a wide range of organisms. The dull red berries that appear in early fall are a favorite for birds and squirrels. They persist throughout the winter, providing food at a time when little else is available. If you look at the leaves on the tree during summer and autumn, you will see that they are chewed up. This is a good thing, as it means that the hackberry is furnishing food for a lot of insects. In particular, the Hackberry is a host plant for butterflies including the Hackberry Emperor and the Tawny Emperor.
An interesting insect that is frequently found on hackberries is the Nipple Gall Psyllid. The adult psyllids resemble tiny cicadas. They spend the winter as adults, then mate in the spring and lay their eggs on the leaves or stems of hackberry trees. After the eggs hatch, the baby insects begin to develop inside small swellings on the underside of the leaves or stems. These swellings, called galls, function as nurseries for the baby insects, protecting them from predators while providing them with food from the inside of the leaf. Nipple galls are extremely common on hackberries; they can even cause leaves to die, but seldom do any long-term damage to the tree.
Stimulating gall production is a very common strategy used by some species of insects to protect and feed their young. On another stop on this tour, we will see a very different kind of gall on the underside of leaves on the American Elm.