War on Weeds—weeds are everybody’s problem
Photo courtesy of Steve Dewey, Utah State University, Bugwood.org
THE ISSUE: Siberian elm
Siberian elm (Ulmus pumila) is an invasive tree native to northeastern Asia. It was introduced into the U.S. in the 1860s for ornamental purposes. It invades roadsides, ditch banks, pastures, waste areas, and other sites. It can quicky invade new areas and it is capable of hybridizing with native elm trees.
Siberian elm can grow up to 70 feet tall. Leaves are approximately 1-2 inches long, elliptical in shape, with toothed margins. Its leaves are significantly smaller than that of the native American elm. Bark is dark brown and is relatively smooth, as trees mature, the bark develops shallow furrows. Flowers are green in color, are just over ¼” long, and are formed in clusters of 6-15. Flowers appear early in the spring before leaves fully develop. As flowers mature, they form papery coin-shaped fruits that house seeds.
Integrated Pest Management (IPM) Options:
• Prevention— Learn to identify this plant. Never transport unknown plant material.
• Mechanical— Hand digging or pulling can be effective during the seedling stage. Make sure to remove as much of the root system as possible, to prevent the tree from resprouting. Cutting down a mature tree can be effective if chemical control is also used, otherwise the stump will likely resprout.
• Cultural— Plant competitive beneficial vegetation. Use management practices that will benefit desirable vegetation. In planting beds, a layer of mulch (at least 3 inches deep) can help to reduce the germination of seedlings.
• Chemical— Seedlings can be treated with a systemic post-emergent herbicide like Glyphosate. Care should be taken when using glyphosate as it is a non-selective herbicide and will also kill desirable vegetation. To control mature trees, cut them down and immediately paint the outside rings of the stump surface (just inside of the bark) with glyphosate. Always read and follow herbicide label directions!
Justin Hatch, University of Idaho Extension Agriculture Educator in Caribou County. 208-547-3205 [email protected]
