Siberian elm (Ulmus pumila) is a tree species introduced to the United States in the 1860s. It was initially valued for its hardiness and rapid growth. Its adaptability has allowed it to become widely established, often appearing as numerous fast-growing seedlings in disturbed areas.
Identifying Siberian Elm Seedlings
Recognizing Siberian elm seedlings involves observing their distinct physical characteristics. Leaves are typically small (one to three inches long, one-third to one inch wide), elliptic to lance-shaped with serrated (saw-toothed) margins and a pointed tip. The leaf base is often only slightly uneven where it attaches to the stem, and leaves are arranged alternately along the twig.
Young stems and twigs are slender, sometimes appearing greenish-brown and slightly hairy when newly emerged, gradually becoming smoother and gray-brown with age. Seedlings often display a compact, upright growth. Their first true leaves generally resemble miniature versions of the mature foliage. Distinguishing Siberian elm from similar plants, such as Chinese elm or native alders, is possible by noting the consistent alternate leaf arrangement and smaller, less uneven leaf bases compared to native elms.
Growth Habits and Ecological Impact
Siberian elm seedlings exhibit rapid growth, quickly establishing themselves. Mature trees can reach 50 to 70 feet. Their widespread presence is due to prolific seed production; a single tree generates thousands of flat, winged seeds (samaras) dispersed by wind. High germination rates lead to numerous new seedlings, often forming dense thickets.
This tree thrives in diverse environments, including poor, dry soils, cold climates, and areas experiencing drought. It readily colonizes disturbed sites such as roadsides, pastures, and grasslands. Siberian elm seedlings outcompete native vegetation for light, water, and nutrients. Their extensive, shallow root systems displace understory plants, reducing local biodiversity and altering ecosystems.
Controlling and Removing Seedlings
Managing Siberian elm seedlings effectively involves direct removal methods and preventative strategies. For newly emerged seedlings, hand-pulling or hoeing is effective. For larger seedlings, using a shovel or specialized weed tool for grubbing works. When employing manual methods, ensure the entire root system is removed to prevent resprouting.
Mechanical control, such as mowing or cutting, can address larger groups of seedlings or saplings. However, these methods often require repeated applications because Siberian elms can resprout vigorously from cut stumps or remaining root fragments. For more established saplings, a follow-up chemical treatment is beneficial. Herbicides like glyphosate or triclopyr are commonly used.
A cut-stump treatment involves applying the chemical directly to the freshly cut surface, specifically to the cambial layer just inside the bark. Basal bark treatments, involving spraying the lower portion of the stem with an oil-based triclopyr solution, are effective for smaller, uncut stems. Always follow product label instructions and local regulations to ensure safe application. Summer, when the tree is actively growing, is often the most effective time for herbicide treatments.
Preventing new seedlings involves applying mulch to suppress germination, regularly weeding disturbed areas, and removing nearby mature Siberian elm trees that serve as seed sources. Reseeding areas with desirable native plants can also help them outcompete any new elm seedlings.