Minnesota Profile: Eastern Leatherwood (Dirca palustris)

Name: If you pull on a strip of the strong, flexible bark, you will understand why this shrub is called leatherwood. A branch might be partially ripped off by falling trees or the subsiding snow pack, but the tough bark stays connected, keeping the branch alive. Branches are exceptionally flexible. The wood is lightweight because lignin, a compound that strengthens wood, comprises less than 10 percent of the wood. (Most north woods trees are 20 to 30 percent lignin.)

Appearance and growth: Maximum height is 10 to 12 feet. New buds appear in autumn after "hiding" in the bases of leaf petioles during summer. New shoots elongate like an extending telescope. Shoots and leaves grow mainly during May.

Regeneration: Many pairs of delicate yellow flowers burst forth in late April. Fruits change from green to yellow green as they mature. Seeds drop like rain in early July. Life on the forest floor is precarious for seeds and seedlings because they are bite-sized morsels for rodents. Sometimes new plants sprout from the base of the shrub and, rarely, from branches partly buried in leaf litter.

Occurrence: Look for it in forests on moist, rich soil-often growing with sugar maples. It occurs in the eastern United States. Similar species have limited ranges in Mexico and the San Francisco Bay area.

Defense: Ever wonder how plants protect themselves against hungry critters? Leatherwood does a better job than many other woody plants in Minnesota. Rarely browsed by deer, its defense seems to combine tough bark with chemicals that taste bad and cause digestive problems or worse if swallowed. These defense chemicals also affect humans. Writings from the 1800s mention use of extracts made from bark and fruit as a purgative. The bark is also believed to cause an allergic skin reaction, but I have handled it and not been affected.

Human uses: Leatherwood makes an attractive landscaping plant because of its interesting branch architecture, abundant early flowers, and compact growth form in shaded or open areas. Indian people used the inner bark for fish line and cordage. When moistened, the bark is flexible enough to use in basketry.

John Zasada, research forester, Forestry Sciences Laboratory