Winter Weed Control: Siberian elm

The issue: Siberian elm (Ulmus pumila) is an invasive, woody plant from central Asia. It has one redeeming quality; it will grow almost anywhere. The problem is that it grows almost everywhere.

Siberian elm is extremely weedy. Early spring seeds blow in the wind, and collect and germinate in cracks and crevices. The fruit (seeds) are shaped like a half-nch flying saucer. Siberian elm trees are large, fast-growing, and have very brittle wood. Even a gentle breeze will cause small branches to break and litter the ground. Large branches threaten nearby structures and power lines. It is common to see Siberian elm volunteer along ditch banks, fence lines, in poorly managed pastures and in landscapes. Siberian elm trees are ugly, dangerous, and make for poor neighbor relations. This species is in the running for the “worst tree ever” competition. They need to be removed — sooner is better.

Siberian elm does produce sprouts or suckers from the stump after mechanical removal. Root suckers are not as common as some other species.

Integrated pest management options:

· Mechanical: Mechanical removal should be combined with herbicide treatment. Young seedlings may be pulled from moist soil. Girdling in late spring has been effective, but it takes a couple of years to starve the roots.

· Cultural: None.

· Biological: Browsing goats help control re-growth after mechanical removal.

· Chemical: Frill cut or cut-stump with glyphosate or triclopyr on large trees, and basal bark with triclopyr on smaller trees are effective herbicide application techniques (see previous posts on the techniques). Be sure the target weed and crop or landscape situations are listed on the product label. Always read and follow herbicide label directions.

Combine them: Seeds can remain dormant for several years, so a long-term control program is important. Combine different IPM options to help improve the effectiveness of your efforts.

For more information, contact Ron Patterson, University of Idaho Extension horticulture/agriculture educator in Bonneville County.