Fall 2020 Conservationist

By the Bark

by Dave Andrusyk, Fullersburg Woods Nature Education Center


The fall color show may be over, but that doesn’t mean you can’t easily identify the trees you pass along the trails. Bare trees still have many tricks up their branches, and bark is one of them.

Bark comes in a variety of colors and textures depending on the type of tree, from smooth and unbroken to scaly and peeling. Some is even quite rough with distinctive ridges (the part that sticks out) and furrows (the part that goes deep into the tree). Characteristics like these can make it easy to ID trees as you walk through the leafless woodlands.

As you increase your observational skills, pay close attention, and you may see details in the bark you never noticed before.


Smooth Bark

Quite a few saplings start out with smooth bark, which can make early identification a challenge, but only a few trees and shrubs remain smooth as they mature. One is musclewood, or American hornbeam. This small tree’s bark gives off a blueish-green hue and has smooth ridges that resemble a flexed muscle. (Scientists refer to these as “fluted” ridges.) You can find musclewood on a walk along the Riverbend Trail at Fullersburg Woods in Oak Brook.


Deep Ridges and Furrows

Black walnut is covered in dark gray to black bark with furrows and ridges that create a boxlike pattern. (Of course you can also ID walnut trees by looking for the fallen nuts and shells around the base.) You can find the large canopies of black walnuts growing among the oaks at several forest preserves, such as at Waterfall Glen in the Bluff Savanna near the Des Plaines Overlook.

The furrows along the gray to whitish bark of a white oak are more random. Some white oak bark can even look mottled as if it’s covered in light-colored splotches. These splotches are a type of fungal infection called “smooth patch,” which causes the top part of the bark to split off from the tree. Smooth patch is not harmful to a white oak, but it does make identifying the tree a lot easier.

The bark on a northern red oak, on the other hand, is almost black. It’s long furrows extend all the way up the trunk and can look like stripes or the runs on a ski slope. Red and white oaks grow together in many forest preserve woodlands.

Peeling or Shaggy Bark

As its name suggests, river birch is typically found along streams and rivers, but it also grows in low wet woodlands. Its brownish to reddish-brown bark looks shredded or curled. Several specimens grow along the river birch “allée” (a landscaped lane of intentionally planted trees) at St. James Farm in Warrenville.

A more common shaggy-barked tree is the aptly named shagbark hickory. The bark on these large trees separates into long scales that look as if they’re peeling off the tree. Shagbarks grow in oak woodlands throughout DuPage forest preserves, including at Blackwell in Warrenville.


Knobby Bark

The common hackberry starts out as a smooth-barked sapling, but as it grows into a medium to large tree it develops bumpy “knobs” on its bark that turn rough and scaly. These knobs are sizable and grow randomly throughout the trunk. This distinctive knobby bark makes the common hackberry easy to ID. The tree grows in woodlands alongside oaks and hickories, and a few dot the grounds at Herrick Lake in Wheaton near the main parking lot.