United States Department of Agriculture Field Guide for Managing Siberian Elm in the Southwest Forest Southwestern Service Region TP-R3-16-17 Revised June 2017 Cover Photos Top left: John M. Randall, The Nature Conservancy, Bugwood.org Lower left: John M. Randall, The Nature Conservancy, Bugwood.org Lower right: Richard Old, XID Services, Inc., Bugwood.org Lower center: Steve Hurst, USDA-NRCS Plants Database, Bugwood.org In accordance with Federal civil rights law and U.S. Department of Agriculture (USDA) civil rights regulations and policies, the USDA, its Agencies, offices, and employees, and institutions participating in or administering USDA programs are prohibited from discriminating based on race, color, national origin, religion, sex, gender identity (including gender expression), sexual orientation, disability, age, marital status, family/parental status, income derived from a public assistance program, political beliefs, or reprisal or retaliation for prior civil rights activity, in any program or activity conducted or funded by USDA (not all bases apply to all programs). Remedies and complaint filing deadlines vary by program or incident. 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Submit your completed form or letter to USDA by: (1) mail: U.S. Department of Agriculture, Office of the Assistant Secretary for Civil Rights, 1400 Independence Avenue, SW, Washington, D.C. 20250-9410; (2) fax: (202) 690-7442; or (3) email: [email protected]. USDA is an equal opportunity provider, employer and lender. Printed on recycled paper Siberian elm (Ulmus pumila L.) Elm family (Ulmaceae) Siberian elm is common in southwestern States and is listed • Clusters of 2 to 5 small, green, drooping flowers as a noxious tree in New Mexico. This field guide serves as without petals occur from February through April before leaves develop. the U.S. Forest Service’s recommendations for management of Siberian elm in forests, woodlands, and • Reproduces primarily via seed; roots re-sprout when rangelands associated with its Southwestern Region. The top growth is damaged. Southwestern Region covers Arizona and New Mexico, • Clusters of smooth, circular, winged, samara-type which together have 11 national forests. The Region also fruit with single seed in the center occur from April to administers 4 national grasslands located in northeastern May. New Mexico, western Oklahoma, and the Texas panhandle. Ecology Description Impacts/Threats In moist environments, Siberian elm (synonyms: Asiatic With adequate soil moisture, Siberian elm germinates elm, dwarf elm, and Manchurian elm) is a fast-growing, readily and grows rapidly. It quickly out-competes hardy, mid-sized (60 to 70 feet tall), deciduous tree. In drier desirable native plants, especially in sparsely vegetated or locations, it is smaller and takes on a shrubby appearance. disturbed areas. A high density of Siberian elm can reduce Siberian elm has an open crown with upward-growing shade-intolerant species (including quality forage) and branches and many flexible, pendulous, brittle branchlets decrease overall species diversity. that easily break off. There is usually a large accumulation Site/Distribution of leaves and woody litter that build up in the understory Siberian elm prefers open areas but tolerates a wide range beneath Siberian elm. Siberian elm is often confused with of conditions, which includes long periods of drought, cold Chinese elm, Ulmus parvifolia, which grows only to 30 to winters, poor soil conditions, high winds, and low 40 feet in height and typically has leaves longer than 2 moisture. In the Southwest, it commonly grows on inches. disturbed grounds, moist streambanks, pastures and rangelands, and rights-of-way along roads and railroads. Growth Characteristics Siberian elm does not tolerate flooding and seldom invades • Deciduous tree (up to 70 feet tall) with an open, mature forest because of its high requirement for sunlight. rounded crown that is 3/4 as wide as it is tall; slender, spreading branches. Spread Siberian elm seed is primarily dispersed via wind, although • Trunk has rough grey or brown bark with shallow, seed may also be transported by water and animals. Seed irregular furrows. may be carried long distances by adhering to surfaces and • Twigs are silver-grey, yellowish, or grayish-brown, undercarriages of logging equipment and vehicles. The tree zigzag-shaped with a leaf bud at each bend and is still sold commercially and is used for shade, scattered spots (lenticels). shelterbelts, and windbreaks in Oklahoma and Texas. • Alternate leaves; 0.5 to 2.5 inches long, tapered at Invasive Features each end with a simple serrate or entire margin; Siberian elm can dominate new locations in just a few upper surface deep green; lower surface paler green years due to its adaptability, high rate of seed production with hairs along vein axils. Leaves may turn yellow and germination, and rapid growth. in autumn. 1 Management Manual Methods It is very difficult to restore native plant communities with Hand removal – Newly emerged seedlings and saplings large infestations of Siberian elm. However, populations with a stem diameter less than 3/8 inch are easily removed can be reduced with careful planning and long-term by hand pulling or hoeing. Small trees with a stem actions. Consider the following actions when planning a diameter between 3/8 and 2.5 inches may be hand management approach: grubbed with a shovel, hoe, or weed tool such as the Weed Wrench™ or Root Talon™. • Maintain healthy and diverse plant communities to prevent or limit Siberian elm infestations. Suppression by cutting – In areas with just a few large trees, trunks may be cut close to the ground to remove top • Limit disturbance and/or promptly revegetate growth. Anticipate that root and trunk re-sprouts will disturbed areas with desirable perennial forage return later in the growing season and will require species, especially perennial grasses. repeated follow-up cutting. Cutting is more effective • Detect and eradicate new populations of Siberian when followed up with a chemical treatment (see cut- elm as early as possible. stump treatment in the “Chemical Control” segment • Combine mechanical and chemical methods for below). most effective Siberian elm control. Girdling – In late spring to midsummer on larger trees, • Implement monitoring and a follow-up treatment use an ax, saw, or chain saw to make two horizontal, plan for missed plants and seedlings. circumferential cuts around the entire trunk. Place one cut 3 to 4 inches above the other through the bark and • Map and keep annual records of reported cambial tissue. Using a blunt object, such as the ax head, infestations. knock off and remove the bark between the cuts. Care Table 1 summarizes some management options for should be taken to remove only the bark and outside controlling Siberian elm under various situations. Further cambial tissue while minimizing damage to the wood details on these management options are explained below. (xylem). Deeper cuts made into the wood often trigger Choice of which method(s) to use will depend on a Siberian elm into re-sprouting from the roots. Leave number of factors including where the population is girdled trees in place for 2 to 3 years and check located and the stage of tree life. Consider carefully the periodically to ensure that cut edges in the bark do not current land use and site conditions (accessibility, terrain, grow together again. See the “Chemical Control” segment microclimate, other flora and fauna present, etc.). Other below for information about combining girdling with a important considerations include treatment effectiveness, herbicide application. cost, and the number of years needed to achieve control. Mechanical Methods More than one control method may be needed for a Tractor-mounted grubbing implements are especially particular site. useful for control of scattered individual trees. A grubbing Physical Control tool mounted as part of a tractor’s front hydraulics can drive a blade into the soil to sever below the root crown To control Siberian elm, it is necessary to destroy the root and uproot the plant onto the surface. Grubbed Siberian system. Physical control can be done on a range of elm should be piled, dried, and burned or mulched rather scales—from individual plant removal (from hand tools to than left on the surface to prevent the plant from re- excavators) to broad-scale clearing (from tillers to rooting. After treatment, it is necessary to monitor bulldozers). Mechanical clearing often requires repeated grubbed areas for 2 or 3 years and re-treat as necessary. applications. 2 Table 1. Management options* Site Physical Control Cultural Control Biological Chemical Control Control Roadsides, Seedlings (< 3/8" diam.) and Use seed, mulch, and fill Consider Light infestations: for trunks < irrigation ditches, saplings (3/8 to 2.5" diam.): dig materials certified to be intensive, short- 3' diam. and less than 8' tall, use fence lines, or or grub with shovel, hoe or weed weed-free. term grazing of basal bark treatment; for trunks non-crop areas tool. seedlings and > 3" diam., girdle or use cut- Train road crews to identify young trees with stump with herbicide. Small trees (2–3" diam.): remove and report infestations along male goats.