ST CROIX VALLEY Work Day

by Evanne Hunt | Apr 28, 2026

Learn how to girdle Aspen trees

Join us as we girdle a clone of Aspen trees at the Alexander Oak Savanna.  Learn how to use a “spud” tool.

Date:  May 11 (Monday)
Time:  9:30am until about 11am
Address:  7829 WI-65, River Falls, WI 54022
Directions:  Take highway 35 south towards River Falls.
Take highway 65 south (35 turns into 65) toward Ellsworth.
Gravel road entrance is on the right just after the Town of River Falls town hall.

Map to location

Aspens are Native

Aspen are native trees but remain undesirable inhabitants of prairies and oak savannas. Aspen are capable of spreading rapidly and crowding out other vegetation. Aspen are pioneer trees on open, burned, or cut-over land. Although important economically in the paper industry, they are a menace in prairies and oak savannas, and eradicating them became an early goal of our restoration.

Although aspens grow from seeds, the primary spread is asexual by underground runners. The typical aspen “grove” is a multi-stemmed clone in which all the roots are interconnected. If an injury to a root occurs, there will be a rapid response by the clone, and new shoots (“suckers”) will be sent up all over the area. New shoots have been known to arise as far as 50 feet from the nearest aspen tree! The clone may expand simultaneously in several directions, as influenced by environmental conditions. In the western United States, huge aspen clones have been found, the largest occupying over 100 acres. In our part of the country, aspen clones are smaller but are often more than an acre in extent.

Girdling

When looking at a large aspen clone, it may be tempting to go in with a chainsaw and cut it down. Wrong! The roots remain alive and immediately send up a huge number of new shoots. An area that had perhaps 5 or 10 large aspen trees will soon have hundreds of aspen stems.

There is only one certain way of killing aspen and this is by girdling.

Girdling means stripping a layer of bark and the underlying cambium and phloem in a band around the trunk. The phloem vessels translocate sugars and other nutrients to the roots, so if the phloem tubes are broken, the roots become starved of food. The xylem vessels, which translocate water to the leaves, are not affected by girdling. With girdling, the upper part of the tree still remains alive, since photosynthesis can continue. Eventually, however, the roots die, and the whole tree dies. The first year after girdling, the clone may appear almost normal, but by the second year, the clone usually dies. The dead trunks can then be cut without stimulating resprouting.

For girdling to be effective the whole clone must be treated. It is also important to make the girdle in such a way that the underlying xylem is not damaged. Damage to the xylem sends signals to the tree that something bad has happened, and the tree then sends up shoots.

Girdling is done in May or early June when the sap is running fast and the tree is growing. At that time, the bark can be easily cut and the girdled bark stripped off. Later in the summer, it is virtually impossible to do a girdle properly.