Northern China, eastern Siberia, Manchuria and Korea
Siberian elm is a fast-growing
tree in the elm family (Ulmaceae) distinguished by small toothed leaves about
1-2½ in (3-7 cm) long and half as wide, and pointed at the tip. Unlike
other elms, the leaf base is usually symmetrical, forming a nearly even "V".
Leaves are smooth and dark green above, paler and nearly hairless beneath,
and alternate from side to side along twigs. Mature trees reach a height
of 50-70 ft. (16-22 m.), with a round crown of slender, spreading branches.
The bark is rough, gray or brown, and shallowly furrowed at maturity. Twigs
are nearly hairless with small, blunt buds. Flowering occurs in the springtime.
The small greenish flowers lack petals and occur in drooping clusters of
2 to 5. After flowering, a single seed forms in the center of each smooth,
flattened, circular, ½ in (10-15 mm) wide fruit.
Other species of elms (Ulmus) and the
close relative Zelkova, especially younger plants, look similar to
Siberian elm. Some may even confuse it with choke-cherry (Prunus serotina)
and hackberry (Celtis sp.). The native slippery elm and American elm
typically have leaves that are greater than 3 in (7.3 cm) long, with unequal
heart-shaped leaf bases, and leaf margins with double teeth.
Dry to mesic prairies
and stream banks are vulnerable to Siberian elm invasion. Thickets of seedlings
soon form around seed-producing trees, bare ground areas, animal and insect
mounds, and other disturbed areas. Wind
carries seed to distant areas where new colonies can form. This tough exotic
survives under conditions not easily tolerated by other species, allowing
it to take advantage of open ground and resources otherwise used by native
plants. Fast growing seedlings of Siberian elm quickly overtake native vegetation,
especially shade-intolerant species. This often leads to invasion by additional
weedy species, compounding the problem.
IN THE UNITED STATES
Siberian elm is known to occur in 43 states (USDA
PLANTS Map) and reported to be invasive in natural areas in 25 states
HABITAT IN THE UNITED STATES
mesic prairies and areas along stream banks in Minnesota and forested areas
and high elevations in Arizona.
Siberian elm was introduced
to the U.S. in the 1860's for its hardiness and fast growth in a variety
of moisture regimes and habitats, including droughts and cold winters. It
is resistant to Dutch elm disease. This elm continues to be promoted, especially
in the Great Plains in spite of weak limbs and susceptibility to insect attack.
BIOLOGY & SPREAD
Seeds are produced
early in spring and spread by the wind. Germination rate is high and seedlings
soon establish in the bare ground found early in the growing season.
long term management of Siberian elm, reduction of seed sources is essential.
To avoid resprouts after cutting
or girdling, cut stumps may be treated with systemic herbicides such as glyphosate
(e.g., Roundup®) and triclopyr (e.g., Garlon). After spring sap flow ceases
and during the growing season, Minnesota DNR State Parks Southern Region
Resource Management apply 4 parts water to 1 part glyphosate (based on 41%
active ingredient glyphosate concentrate) with a hand sprayer to cut stumps.
The entire stump should be saturated with the herbicide to achieve the most
effective control. Garlon® 4 (triclopyr ester formulation) can be applied
as a cut stump or basal bark treatment. For basal bark, apply a 20-percent
solution in horticultural oil (2.5 quarts per 3-gallon mix) with a penetrant
(check with herbicide distributor) to young bark as a basal spray in winter
(January to February) or summer-fall (June to October). Cut stems can be
immediately treated with glyphosate herbicide as a 20-percent solution (2.5
quarts per 3-gallon mix) in water with a surfactant.
During the growing season, seedlings
can be hand pulled and small trees carefully removed by a grub hoe or weed
wrench. Trees girdled in mid-May to early July will die over 1-2 years without
sprouting if cut properly. To remove a band of bark from the wood, make two
parallel cuts 3-4 inches apart, then knock bark off with a blunt object such
as the back of an axe head or dull end of a girdling bar. The xylem must
remain intact; if girdled too deeply the tree will respond as if cut down
and will resprout. On sites with few seed sources, the large trees can be
cut down and resprouts trimmed as needed.
A regular regime of prescribed
burning in fire-adapted communities will kill seedlings.
USE PESTICIDES WISELY: ALWAYS READ THE ENTIRE PESTICIDE LABEL CAREFULLY, FOLLOW ALL MIXING AND APPLICATION INSTRUCTIONS AND WEAR ALL RECOMMENDED PERSONAL PROTECTIVE GEAR AND CLOTHING. CONTACT YOUR STATE DEPARTMENT OF AGRICULTURE FOR ANY ADDITIONAL PESTICIDE USE REQUIREMENTS, RESTRICTIONS OR RECOMMENDATIONS.
NOTICE: MENTION OF PESTICIDE PRODUCTS ON THIS WEB SITE DOES NOT CONSTITUTE ENDORSEMENT OF ANY MATERIAL.
For more information on
the management of Siberian elm, please contact:
- Ian Torrence, National Park Service,
Ian_Torrence at nps.gov
- Lori Makarick, National Park Service, Lori_Makarick at nps.gov
- Kelly Kearns, Wisconsin Department of Natural Resources, Kelly.Kearns at dnr.state.wi.us
SUGGESTED ALTERNATIVE PLANTS
shade trees near prairie sites, consider using trees native to your area,
especially those that are not prolific colonizers. Some appropriate examples
are bur oak (Quercus macrocarpa) or other oaks native to your area,
and basswood (Tilia americana). Check with your state native plant
society or the Lady Bird Johnson Wildflower Center's Native
Plant Information Network for recommendations.
Susan Wieseler, Minnesota Department of Natural
Resources, Rochester, MN
Sally Canning, Phillip D. Moore, Lori Makarick, and Ian Torrence.
Jil M. Swearingen, National Park Service, Center for Urban Ecology, Washington, DC
U.S. Department of Agriculture PLANTS Database
Brown, R.G. and M.L. Brown. 1972.
Woody Plants of Maryland. Port City Press, Baltimore, MD. 347 pp.
Kennay, J. and G. Fell. 1990. Illinois
Vegetation Management Guideline: Siberian elm (Ulmus pumila). Illinois
Nature Preserves Commission, Springfield, Il.
Rehder, A. 1940. Manual of Cultivated
Trees and Shrubs, 2nd ed. MacMillan Co., New York. 996 pp.
Remaley, T. 2000. Southeast Exotic
Pest Plant Council Invasive Plant Manual. In Bargeron, C.T., D.J. Moorhead,
G.K. Douce, R.C. Reardon & A.E. Miller (Tech. Coordinators). 2003. Invasive
Plants of the Eastern U.S.: Identification and Control. USDA Forest Service
- Forest Health Technology Enterprise Team. Morgantown, WV USA. FHTET-2003-08.
Swearingen, J. 2009. WeedUS Database of Plants Invading Natural Areas in the United States: Siberian Elm (Ulmus pumila). http://www.invasive.org/weedus/subject.html?sub=3479.
USDA, NRCS. 2009. The PLANTS Database (http://plants.usda.gov). National Plant Data Center, Baton Rouge, LA 70874-4490 USA.
Plant Conservation Alliance, Alien Plant Working Group.