SPECIES CHARACTER
Description
The greenish-yellow inflorescence of leafy spurge is borne in an umbel pattern
and typically blooms from May-October. Each umbel supports 7-10 groups of tiny,
incon- spicuous, flowers, subtended by 4 crescent-shaped glands and two
conspicuous greenish-yellow bracts.
The bluish-green leaves of leafy spurge are usually alternate except for those
located immediately under the inflorescence. These are in a whorled
arrangement. Another characteristic is the two kinds of leaves present on the
stem: leaves located on the lower half of the stem are scale-like, while those
on the upper portion are linear to oblong. Leafy spurge has milky white sap.
Similar Species
The most conspicuous features to look for when identifying leafy spurge from
other plants are its greenish-yellow inflorescences; alternate, linear to
slightly oblong or scaly leaves; and milky-white sap that flows readily upon
injury to the plant. Leafy spurge should be accurately identified before
attempting any control measures. If identification of the species is in doubt,
the plant's identity should be confirmed by a knowledgeable individual and/or by
consulting appropriate books.
Distribution
Native to Europe and temperate Asia, leafy spurge currently is found throughout
the world with the exception of Australia. It was probably introduced into the
United States as a contaminant in imported grain. Since its invasion, the plant
has become a serious management problem, particularly for the north and central
plains states. This plant is recorded from 21 counties in the northern half of
Illinois, but it has not become a serious nuisance yet.
Habitat
This deep-rooted perennial plant is adapted to a wide range of soil moisture
conditions from moist to dry. However, the spurge is aggressive especially in
very dry situations where competition from native species is less intense.
Areas most sensitive to leafy spurge infestation include pastures, roadsides,
abandoned fields, railroad ballasts, disturbed and undisturbed mesic to dry
prairies, and possibly open natural communities such as savannas.
Life History
Leafy spurge emerges in the early spring when temperatures still fluctuate
around freezing. Seedlings at this time may be deep red or purplish in color.
As the temperature rises, the stems grow rapidly and, if the plant is over a
year old, flowers may appear as early as May. After 4-6 weeks, each stalk may
produce and disperse over 200 seeds with a germination rate of 60-80%.
However, in spite of this impressive germination rate, the key reproductive
capabil-ities of leafy spurge remain underground. The root system of the
plant is very extensive. Vegetative reproduction from both crown buds and root
buds explain not only the persistence of this weed, but the difficulties
encountered in eradicating it as well. Even if the foliage of the plant is
removed or destroyed, the living root tissue will regenerate new shoots, and the
new shoots can emerge from buds located anywhere along the length of the root.
Effects Upon Natural Areas
If leafy spurge becomes well established in Illinois, it will threaten mesic to
dry prairies.
Current Status
Fortunately, leafy spurge has not heavily invaded Illinois. However, scattered
populations have been observed in some portions of northeastern Illinois and
pose a serious threat. Left unchecked, just a few plants may easily disperse
themselves along interstate highways and right-of-ways.
CONTROL RECOMMENDATIONS
Leafy spurge is well established in the central plains states where much time and
effort is spent trying to find a control. Most agree that the key to stopping
this pest revolves around the ability to destroy its root system and, until a
biological control can be found, herbicides appear to be a temporary solution.
Picloram (trade name Tordon) currently is being used on rangelands, but it may
be several years before researchers can determine its effectiveness.
The best way to inhibit this nuisance plant from becoming as destructive as
purple loosestrife and multiflora rose is to recognize it as a pest now; treat
the initial invading populations and prevent it from spreading any farther.
In Illinois, it is important to remember that the sooner you attack leafy
spurge - in its first year if possible - the better the chances of controlling
it. All methods below may need to be repeated for 5-10 years.
Prescribed burning and herbiciding
Fire in conjunction with herbicides may be more effective than either method
alone. Burning stimulates vegetative growth, making the plant more vulnerable
to herbicides. Plants can be sprayed with 2,4-D in autumn (September) and
burned the following spring (April). This should be followed by another 2,4-D
treatment in June and a fall burn in October. The process may have to be
repeated many times.
For top growth control, the herbicide 2,4-D amine can be sprayed on the foliage
in a 25% solution (1 part 2,4-D in 4 parts water) twice a year. The most
effective time to apply the herbicide is mid- to late June when the true
flowers (not the bracts) begin to appear. The second spray application should
be made early to mid September when fall regrowth has begun but before a
killing frost occurs.
The nonselective herbicide Roundup (a formulation of glyphosate), sprayed on
leafy spurge foliage as a 33% solution (1 part Roundup in 3 parts water), will
provide 80-90% top control if applied between mid-August and mid-September. A
follow-up treatment with a 25% solution of 2,4-D amine between mid-June and mid-
July of the following year is necessary to control seedlings.
Apply the herbicide with a hand-sprayer until the spray coverage is uniform and
complete. Do not spray so heavily that herbicide drips off the target species.
Roundup is a nonselective herbicide that kills grasses and broadleaf plants.
2,4-D is a selective herbicide that kills broadleaf plants, but not grasses.
Try to spray leafy spurge only, and carefully avoid contacting nontarget
species. Native nontarget plants will be important in recolonizing the site
after leafy spurge is controlled. The herbicide should be applied while
backing away from the areas to avoid walking through the wet herbicide. By
law, herbicides only may be applied according to label instructions and by
licensed herbicide applicators or operators when working on public
properties.
FAILED OR INEFFECTIVE PRACTICES
Mowing or hand cutting is not completely effective because the root remains
undamaged and new sprouts will reappear rapidly. Also, mowing would have to be
done continuously because it stimulates development of inflorescences on the
lateral branches.
Hand-pulling, digging, or tilling is not completely effective because the
entire root system must be excavated for complete control of leafy spurge.
Pulling and digging can rip or cut the root into smaller pieces, leaving
portions to resprout. This method could actually increase the number of
plants.
REFERENCES
The Nature Conservancy Element Stewardship Abstract for Euphorbia esula - Leafy Spurge. Midwest Regional Office, Minneapolis, MN.
Lorenz, R. editor. 1986. Leafy Spurge News vol 2, issue 2. Land Reclamation Research Center, Mandan, ND.
United States Department of Agriculture, Agricultural Research Service. 1970. Selected Weeds of the United States. Agricutural Handbook No. 366. U.S. Government Printing Office, Washington D.C.
Watson, A. K. editor. 1985. Leafy Spurge Monograph Series of the Weed Science Society of America no 3. Weed Science Society of America, Champaign, Illinois. 104 pp.
PERSONAL COMMUNICATIONS
Panzer, Ron. 1988. Department of Biology, Northeastern Illinois University, Chicago, Illinois.
Written for the Illinois Nature Preserves Commission by:
Maggie Cole
Illinois Department of Conservation
100 First National Bank Plaza
Suite 205
Chicago Heights, Illinois 60411