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Click on the name of each noxious weed for more information:

Canadian Thistle
Mutliflora Rose
Johnson Grass
Purple Loosestrife
SpearThistle
MuskThistle

SPECIES CHARACTER

Description
Canada thistle is a 2 to 5 foot (0.6 to 1.5 meters) tall forb with deep, wide spreading, horizontal roots. The grooved, slender stems branch only at the top and are slightly hairy when young, becoming covered with hair as the plant grows. The oblong, tapering, sessile leaves are deeply divided, with prickly margins. Leaves are green on both sides with a smooth or slightly downy lower surface. Numerous small, compact (3/4 inch or 1.9 cm. diameter), rose-purple or white flowers appear on upper stems from June to September. Seeds are small (3/16 inch or 0.5 cm long), light brown, smooth and slightly tapered, with a tuft of tan hair loosely attached to the tip.

Similar Species
Canada thistle is distinguished from other thistles (Cirsium spp.) by its deep-running perennial rootstocks, more slender stems, and small compact heads. Canada thistle 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
Canada thistle, which is naturalized from Europe, occurs throughout the northern U.S. east of the Rocky Mountains. It is common in the northern half of Illinois and rare in the southern half. This species is very rare in southern Indiana and is not a serious problem in Missouri natural areas.

Habitat
Canada thistle does best in disturbed areas (overgrazed pastures, old fields, waste places, fence rows, along roadsides). It sometimes occurs in wet areas where water levels fluctuate (along stream banks and ditches). It can invade sedge meadows and wet prairies from adjacent disturbed sites. This thistle does not do well in undisturbed prairies, good to excellent pastures, or in woodland. Plants are tall and lax, with few flowers, on sites that are shaded most of the day.

Life History
This dioecious, weedy perennial occurs in patches, commonly in disturbed areas. Introduction to new areas occurs mostly by windborn seed or sometimes by run-off in ditches. It spreads rapidly by rhizomes or root segments. Lateral roots 3 or more feet deep spread from a fibrous taproot. Aerial shoots are sent up at 2 to 6 inch intervals. Basal leaves are produced the first year, flowering stems the next. Pollination is mostly by honeybees, and wind pollination is limited. Most seeds germinate within one year. Some seeds immediately produce rosettes before winter and emerge to flower the next spring. Seeds remain viable in soil up to 20 years in some cases. Emergence occurs in early May, with vertical growth in mid-to-late June. As frequency of Canada thistle increases at a site, species diversity decreases, possibly due to allelopathic substances.

Effects Upon Natural Areas
Canada thistle is an alien species capable of crowding out and replacing native grasses and forbs. It is detrimental to natural areas where it occurs, particularly non-forested communities, and it can change the natural structure and species composition where it becomes well-established. Prairies, barrens, savannas, and glades are susceptible, particularly those sites that have been disturbed and are reverting naturally to native species, as well as those undergoing manipulative restoration management.

CONTROL RECOMMENDATIONS

RECOMMENDED PRACTICES IN NATURAL COMMUNITIES OF HIGH QUALITY
Prescribed fire can be effective in controlling this species and is a preferred treatment. Late spring burns, between May and June, are most detrimental to this noxious weed and should be used when possible. Prescribed burns to control this plant should not be conducted early in the spring, as early spring burns can increase sprouting and reproduction of this species. During the first 3 years of control efforts, burns should be conducted annually.
Management practices that maintain and encourage the development of healthy stands of native species will help prevent establishment of Canada thistle or help shade and weaken plants on sites already infested.
Repeated and frequent pulling or hand-cutting of individual plants will eventually starve underground stems. Cutting or pulling should be at least 3 times each season, in June, August, and September. This treatment is feasible for light and moderate infestations, but may be relatively time consuming in heavy infestations. Spot application of the amine formulation of 2,4-D according to label instructions can control this plant. Individual plants of Canada thistle should be treated with a wick applicator or hand sprayer. The herbicide 2,4-D amine is selective for broadleaf plants. To reduce vapor drift, use an amine formulation of 2,4-D rather than an ester formulation. Precautions should be taken to avoid contacting nontarget plants with the solution. Do not spray so heavily that herbicide drips off the target species. The herbicide should be applied while backing away from the areas to avoid walking through the wet herbicide. By law, herbicides may only be applied as per label instructions and by licensed herbicide applicators or operators when working on public properties.

RECOMMENDED PRACTICES ON BUFFER AND SEVERELY DISTURBED SITES
Control procedures recommended above for high quality natural communities are also applicable to buffer and severely disturbed sites. Additional control measures are as follows. On large sites (old fields, ditch banks, roadsides) with heavy infestations, thistles should be mowed when in full bloom, and as close to the ground as possible. Cut flower-heads should be removed to prevent scattering seeds on site. Repeated mowing may be needed for several years to obtain adequate control.
A foliar application of a 1-2% solution of Roundup (a formulation of glyphosate) applied in spring when plants are 6-10 inches (15.2 -25.4 cm) tall is an effective herbicide treatment. Individual plants should be spot-treated with a wick applicator. Roundup normally kills the entire plant, including the roots, when applied in this manner. Roundup is a nonselective herbicide and precautions should be taken to avoid contacting nontarget plants with the solution. Do not spray so heavily that herbicide drips off the target species. As with 2,4-D amine, Roundup should be applied while backing away from the areas to avoid walking through the wet herbicide. Roundup should not be used in high-quality natural areas during the growing season because of the possibility of harming nontarget plants.
On severely disturbed sites with heavy infestations, such as cropland or abandoned cropland, the site could be plowed and sowed to a cover crop (wheat, alfalfa, rye), if practical and desirable. The following May, the cover crop should be plowed under and desired native species should be seeded.

FAILED OR INEFFECTIVE PRACTICES

Fire early in the growing season can increase sprouting and reproduction. Prescribed burns in late spring are effective, as discussed previously.
Tillage disturbance of soil may provide ideal conditions for reinvasion and for introduction of other exotics.
Grazing is not an effective control measure as the prickles prevent livestock from grazing near Canada thistle.

REFERENCES

Blatchely, W. S. 1930. The Indiana weed book. The Nature Publishing Co., Indianapolis, Indiana. 191 pp.

Evans, J. E. 1984. Canada thistle (Cirsium arvense): a literature review of management practices. Natural Areas Journal. 4(2):11-21.

Gleason, H. A. 1952. The new Britton and Brown illustrated flora of the northeastern United States and adjacent Canada. The New York Botanical Garden. New York. Vol. 3. 595 pp.

Mohlenbrock R. H. 1986. Guide to the vascular flora of Illinois. Southern Illinois University Press, Carbondale. 507 pp.

Moore, R. J. 1975. The biology of Canadian weeds: 13 Cirsium arvense (L.) Scop. Pp. 146-161 in G. Mulligan, ed., The biology of Canadian weeds, contributions 1-32. Information Services, Agriculture Canada, Ottawa, Ontario.

Phillips Petroleum Company. 1956. Undesirable grasses and forbs. Section 3 of series. Bartlesville, Oklahoma. 25 pp.

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.

University of Illinois Agriculture Experiment Station. 1954. Weeds of north central states. North Central Regional Publication No. 36, Circular 718. University of Illinois Agriculture Experiment Station, Urbana. 239 pp.

University of Illinois Agriculture Experiment Station. 1984. Row crop weed control guide. University of Illinois Agriculture Experiment Station and the U.S. Department of Agriculture, Champaign-Urbana. 16 pp.

PERSONAL COMMUNICATIONS

Kurz, Don. 1988. Natural History Section, Missouri Department of Conservation, Jefferson City, Missouri.

McFall, Don. 1988. Division of Natural Heritage, Illinois Department of Conservation, Springfield, Illinois.

Olson, Steve. 1988. Division of Nature Preserves, Indiana Department of Natural Resources, Tell City, Indiana.

Packard, Steve. 1989. The Nature Conservancy, Chicago, Illinois.

Schwegman, John. E. 1988. Division of Natural Heritage, Illinois Department of Conservation, Springfield, Illinois.

Stritch, Larry. 1988. United States Forest Service, Shawnee National Forest, Harrisburg, Illinois.

Photo by Kenneth R. Robertson, INHS

SPECIES CHARACTER

Description
Multiflora rose is a medium height, thorny, bushy shrub with a more spreading then erect growth form. Leaves are born alternately on the stems and divided into 5-11 leaflets (usually 7-9). Each leaflet is broadly oval and toothed along its margin. Clusters of numerous, white flowers, 3/4" - 1-1/2 inches (1.9-3.8 cm) across, blossom in late spring. The fruits are small, firm, red hips that may remain on the plant well into winter. Older rose shrubs may obtain a height of 15 feet (4.6 meters) or more with a root crown diameter of 8 inches (20 cm).

Similar Species
Multiflora rose can be distinguished from Illinois' native roses by the presence of a feathery or comb-like margin on the narrow stipules (a green, leaf-like structure) found at the base of each leaf stalk. Illinois' native rose species all have stipules at the base of the leaf stalk, but stipules of the native roses do not have feathery margins. Also, the styles (floral structures) of multiflora rose are fused together into a column, while all native roses except for prairie rose (Rosa setigera) have separate styles. Multiflora rose 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
Multiflora rose was introduced into Illinois in the 1950's from eastern Asia for wildlife cover and food. Managers recognized that plantings of this thorny, bushy shrub provided excellent escape cover and a source of winter food. Because of its dense thorny nature, the commercial nursery trade began marketing it as a "living fence" as well. The species soon spread and became a serious invader of agricultural lands, pastures, and natural communities throughout Illinois.

Habitat
Multiflora rose occurs in successional fields, pastures, and roadsides. It also may occur in dense forests, particularly near disturbances such as treefall gaps.

Life History
Multiflora rose is named for the clusters of many white flowers born on this perennial bramble during May or June. The flowers develop into small, hard fruits called hips that remain on the plant throughout winter. The great majority of plants develop from seeds remaining in the soil relatively close to plants from which they were produced. Birds and mammals also consume the hips and can disperse them greater distances. Rose seeds may remain viable in the soil for 10-20 years. Multiflora rose also spreads by layering, i.e., where tips of canes touch the ground and form roots, and by plants that arise from shallow roots.

Effects Upon Natural Areas
Multiflora rose readily invades prairies, savannas, open woodland, and forest edges. It is a thorny, bushy shrub that can form impenetrable thickets or "living fences" and smother out other vegetation. It is a serious pest species throughout the eastern United States.

CONTROL RECOMMENDATIONS

RECOMMENDED PRACTICES IN NATURAL COMMUNITIES OF HIGH QUALITY
Pulling, grubbing, or removing individual plants from the soil only can be effective when all roots are removed or when plants that develop subsequently from severed roots are destroyed. These approaches are most practical for light, scattered infestations.
In fire-adapted communities, a routine prescribed burn program will hinder invasion and establishment of multiflora rose.
Research indicates that 3-6 cuttings or mowings per growing season for more than one year can achieve high plant mortality. Such treatment may need to be repeated for 2-4 years. Increased mowing rates (+6/season) did not increase plant mortality. In high quality communities, repeated cutting is preferred over mowing, because repeated mowing will damage native vegetation as well as multiflora rose.
Cutting stems and either painting herbicide on the stump with a sponge applicator (sponge-type paint applicators can be used) or spraying herbicide on the stump with a low pressure hand-held sprayer kills root systems and prevents resprouting. Roundup herbicide (a formulation of glyphosate) has been effective in controlling multiflora rose when used as a 10-20% solution and applied directly to the cut stump. Although the Roundup label recommends a higher concentration for cut-stump treatment (50-100%), this lower concentration has proven effective. With this technique, herbicide is applied specifically to the target plant, reducing the possibilities of damaging nearby, desirable vegetation. Cut-stump treatment is effective late in the growing season (July-September), and also during the dormant season. Dormant season application is preferred because it will minimize potential harm to nontarget species. Glyphosate is a nonselective herbicide, so care should be taken to avoid contacting nontarget species. In addition, Triclopyr (tradename Garlon 3A) can be applied to cut stems or canes for selective control of multiflora rose. Garlon 3A diluted in water at a rate of 50% can be sprayed, using a hand sprayer, to the cut surface. Application should be within a few hours of cutting. Use of Garlon 3A is best done in the dormant season to lessen damage to nontarget species. Great care should be exercised to avoid getting any of the herbicide on the ground near the target plant since some nontarget pecies may be harmed. Avoid using Triclopyr if rain is forecast for the following 1-4 days; otherwise runoff will harm nontarget species. By law, herbicides only may be applied according to label directions and by licensed herbicide applicators or operators when working on public properties.

RECOMMENDED PRACTICES ON BUFFER AND SEVERELY DISTURBED SITES
Repeated cutting, as discussed above, is effective. For large populations on severely disturbed areas, mowing can be substituted for cutting individual plants. However, mowing multiflora rose can result quickly in flat tires. On mowers, filling tires with foam is recommended.
Fosamine (tradename Krenite) can be applied as a foliar spray in a 2% solution plus 0.25% surfactant (2-1/2 ounces of Krenite plus one-half ounce surfactant per gallon of water). The Krenite S formulation contains the appropriate amount of surfactant. Coverage of foliage should be complete. Krenite should be applied only in July-September. No effects will be observed during the autumn season following application. Slight regrowth may occur the following season but canes will die during summer. Fosamine kills only woody species and is non-volatile, therefore it is the preferred foliar spray treatment.
Dicamba (tradename Banvel) is an effective foliar spray that is less preferred than Krenite. Banvel is selective against broadleaf plants, so care must be taken to avoid contacting desirable, broadleaf vegetation. It can be applied as a foliar spray in a 1% solution (1 ounce of Banvel per gallon of water). Though this solution can be applied any time during the growing season, best results are obtained during May and June when plants are actively growing and flowering, following full leaf-out. One-half ounce of a surfactant should be added when treating dense foliage and, to enhance control in late season applications, complete coverage of all green leaves should be achieved. Do not spray Krenite or Dicamba so heavily that herbicide drips off the target species. Foliar spray of herbicides should only be used in less sensitive areas because of problems with contacting nontarget species. By law, herbicides only may be applied according to label directions and by licensed herbicide applicators or operators when working on public properties.
Glyphosate (tradename Roundup) is an effective foliar spray when applied as a 1% solution to multiflora rose plants that are flowering or in bud. Roundup is not a preferred chemical treatment, however, because it is nonselective and the selective herbicides mentioned above are effective. Nevertheless, Roundup can be used as a foliar spray during the growing season on severely disturbed sites if care is taken to avoid contacting nontarget plants. Roundup should not be used as a foliar spray during the growing season in high-quality natural areas because it can result in damage to nontarget species. Roundup is useful as a foliar spray for alien plants that remain green and retain their leaves after native vegetation is dormant or senescent. Multiflora rose does not fit this description adequately and is controlled most effectively when treating during the growing season.

FAILED OR INEFFECTIVE PRACTICES

No effective biological controls that are feasible in natural communities are known. Rose rosette disease is a sometimes fatal viral disease that attacks multiflora rose and other roses. This disease is not considered a useful biological control at this time because it may infect native roses and plums, as well as commercially important plants in the rose family such as apples, some types of berries, and ornamental roses.

REFERENCES

Eckardt, N. 1987. Rosa multiflora. Element Stewardship Abstract. The Nature Conservancy, Minneapolis. 9 pp.

Evans, J.E. 1983. A literature review of management practices for multiflora rose. Natural Areas Journal 3:6-15.

Underwood, J.F. and E.W. Stroube. 1986. Multiflora rose control. Ohio State Univ., Coop. Ext. Serv., Leaflet 303.

PERSONAL COMMUNICATIONS

Glass, Bill. 1989. Division of Natural Heritage, Illinois Department of Conservation, Springfield, Illinois.

Laurie, Dennis. 1989. Lake County Forest Preserve District, Libertyville, Illinois.

Schwegman, John E. 1989. Division of Natural Heritage, Illinois Department of Conservation, Springfield, Illinois.

SPECIES CHARACTER

Description
Johnson grass is a tall, coarse, grass with stout rhizomes. It grows in dense clumps or nearly solid stands and can reach 8 feet (2.4 meters) in height. Leaves are smooth, 6-20 inches (15.2-50.8 cm) long, and have a white midvein. Stems are pink to rusty red near the base. Panicles are large, loosely branched, purplish, and hairy. Spikelets occur in pairs or threes and each has a conspicuous awn. Seeds are reddish-brown and nearly 1/8 inch (0.3 cm) long. Johnson grass 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.

Similar Species
Sorghum halepense with its white leaf vein, wide leaves, and reddish seedhead is distinguished from (1) eastern gamagrass (Tripsacum dactyloides), which has flowers in a spike rather than a loose panicle; (2) switchgrass (Panicum virgatum), which has no white vein and a greenish-yellow seedhead; 3) big bluestem (Andropogon gerardii) and Indiangrass (Sorghastrum nutans) which both have narrower leaves and usually lack a prominent vein.

Distribution
Originally native to the Mediterranean, this grass now occurs in all warm-temperate regions of the world. It is widely distributed in tropical America, common in the southern U.S., and distributed throughout most of Illinois. It is particularly common in cultivated river bottoms in the southern 1/4 of the State, especially along the Mississippi, Ohio, and Cache River bottoms.

Habitat
This species occurs in crop fields, pastures, abandoned fields, rights-of-way, forest edges, and along streambanks.
It thrives in open, disturbed, rich, bottom ground, particularly in cultivated fields.

Life History
Johnson grass is a very aggressive, perennial grass. It occurs in dense clumps that spread by seed and rhizomes to form nearly pure stands. The grass emerges late in spring and forms seed by July 1, reaching a height of 8 or more feet. Stems and leaves die back after the first frost, but the dead litter often covers the ground all winter. Rhizome cuttings commonly form new plants, making it very difficult to eradicate. It spreads rapidly and is not affected by many of the agricultural herbicides.

Effects Upon Natural Areas
Johnson grass invades riverbank communities and disturbed sites, particularly fallow fields and forest edges, where it crowds out native species and slows succession. It quickly dominates the herbaceous flora, reduces plant diversity, and is unsightly to observers. It occurs in disturbed parts of several natural areas such as Lower Cache, Horseshoe Lake, and Robeson Hills. This grass is a serious potential threat in many old fields where succession to forest communities is desired.

CONTROL RECOMMENDATIONS

RECOMMENDED PRACTICES IN NATURAL COMMUNITIES OF HIGH QUALITY
Initial effort in areas of heavy infestation
Johnson grass does not infest areas of high natural quality heavily except for the naturally disturbed environment along river banks in southern Illinois where it is difficult to control selectively. Seed panicles should be cut and removed from the area where practical. Dense patches can be controlled by spraying the foliage with 2% Roundup (a formulation of glyphosphate) during June, just prior to seed maturity. Care should be taken to avoid contacting nontarget plants, since Roundup is a nonselective herbicide. Do not spray so heavily that herbicide drips off the target species. The herbicide should be applied while backing away from the area to avoid walking through wet herbicide. By law, herbicides may only be applied as per label instructions and by licensed herbicide applicators or operators when working on public properties.

Effort in areas of light infestation
Clumps and individual plants may be hand pulled during June, just after a rain when the ground is soft. All plant parts should be removed from the area. Broken stems and roots left in the ground should be dug up if only a small area is involved. It is more effective to spot-treat the individual plants with herbicide than to pull them, and large clumps can be sprayed with 2% Roundup using a hand sprayer or backpack sprayer. Herbicide treatment may need to be repeated for several years to ensure good control.

Maintenance control
Preferred treatment is hand pulling of individual plants immediately upon discovery. All plant parts, including rhizomes, must be removed. It may be necessary to hand pull a population several times to obtain control. Surrounding seed sources should be eliminated where possible to prevent continual reinvasion.

RECOMMENDED PRACTICES ON BUFFER AND SEVERELY DISTURBED SITES
Initial effort in areas of heavy infestation
Repeated and close mowing kills Johnson grass seedlings, prevents seed production, and reduces rhizome growth and regrowth of shoots. Sites may be tilled where it is practical (e.g. abandoned cropland) and the exposed roots left to winter kill. Repeated tillage (e.g. 6 times at 2- week intervals during the growing season) prevents rhizome development and reduces Johnson grass populations. Limited early season tillage, however, encourages rhizome growth by spreading pieces of the rhizomes. In a monoculture, livestock may be used to eliminate the Johnson grass by grazing. Spraying 2% Roundup on foliage using a tractor and power sprayer provides effective control.

Effort in areas of light infestation
Cutting and removal of seed heads during early July and then spot application of 2% Roundup to the foliage usually will be effective if continued for 3-4 years.

Maintenance control
Preferred treatment is same as given above for high-quality areas. Another treatment is spot application of 2% Roundup to eliminate invading individuals the first year and to eliminate all surrounding seed sources.

FAILED OR INEFFECTIVE PRACTICES

ACKNOWLEDGEMENTS

Dr. Robert M. Mohlenbrock and the Southern Illinois University Press generously permitted use of illustrations from their Illustrated Flora of Illinois.

REFERENCES

Bever, W. et al. 1975. Illinois pesticide applicator study guide. Special Publication 39. Cooperative Extension Service, University of Illinois, College of Agriculture, in cooperation with the Illinois Natural History Survey, Urbana-Champaign. 75 pp.

Blatchely, W. S. 1930. The Indiana weed book. The Nature Publishing Co., Indianapolis, Indiana. 191 pp.

Gleason, H. A. 1952. The new Britton and Brown illustrated flora of the northeastern United States and adjacent Canada. Vol 1. The New York Botanical Garden, New York. 590 pp.

Fernald, M. L. 1950. Gray's manual of botany, eighth edition. American Book Co., New York. 1632 pp.

Mohlenbrock R. H. 1986. Guide to the vascular flora of Illinois. Southern Illinois University Press, Carbondale. 507 pp.

Mohlenbrock, R. H.,and J. W. Voigt. 1959. A flora of southern Illinois. Southern Illinois University Press, Carbondale. 390 pp.

Peterson, R. T., and M. McKenny. 1968. A field guide to wildflowers of northeastern and northcentral North America. A Peterson Field Guide Series. Houghton Mifflin Co., Boston, Massachusetts. 420 pp.

Phillips Petroleum Company. 1956. Undesirable grasses and forbs. Section 3 of series. Bartlesville, Oklahoma. 25 pp.

Schwegman, J. E. 1988. Exotic invaders. Outdoor Highlights, mid-March issue, pp 6-11.

Tehon, L. R. et. al. 1946. Illinois plants poisonous to livestock. Extension Service, College of Agriculture, University of Illinois, Urbana. 03 pp.

University of Illinois Agriculture Experiment Station. 1954. Weeds of north central states. North Central Regional Publication No. 36, Circular 718. University of Illinois Agriculture Experiment Station, Urbana. 239 pp.

University of Illinois Agriculture Experiment Station. 1984. Row crop weed control guide. University of Illinois Agriculture Experiment Station and the U.S. Department of Agriculture, Champaign-Urbana. 16 pp.

University of Illinois Cooperative Extension Service. 1971. Illinois agronomy handbook. University of Illinois College of Agriculture, Champaign-Urbana. 59 pp.

Warwick, S. I., and L. D. Black. 1984. The biology of Canadian weeds: 61. Sorghum halapense (L.) Pers. Pp. 396-413 in G. Mulligan, ed. The biology of Canadian weeds, contributions 33-61. Communications Branch, Agriculture Canada, Ottawa, Ontario.

PERSONAL COMMUNICATIONS

Crews, W. 1988. Crab Orchard Wildlife Refuge, United States Fish and Wildlife Service, Marion, Illinois.

Kurz, Don. 1988. Natural History Section, Missouri Department of Conservation, Jefferson City, Missouri.

Schwegman, John. 1988. Division of Natural Heritage, Illinois Department of Conservation, Springfield, Illinois.

Stritch, Larry. 1988. Shawnee National Forest, United States Forest Service, Harrisburg, Illinois.

SPECIES CHARACTER

Description
The most notable characteristic of purple loosestrife is the showy spike of rose-purple flowers it displays in mid to late summer. There are, however, several native species which also produce purple spikes of flowers that superficially resemble those of purple loosestrife. Purple loosestrife can be differentiated from these species by a com-bination of other characteristics. Purple loosestrife has flowers with 5 to 7 purple petals; the leaves are opposite or in whorls of 3, all lacking teeth; and it has a stiff 4-sided stem that may appear woody at the base of large plants. Purple loosestrife is an herbaceous perennial that may be from 3 to 10 feet tall, with an average height of 5 feet, and it flowers from early July to early September.

Similar Species
Purple loosestrife may be distinguished from the native winged loosestrife (Lythrum alatum), which it most closely resembles, by its generally larger size (native loosestrife has an average height of only 2 feet) and its opposite leaves (native loosestrife's upper leaves are usually alternate). The flowers of native loosestrife are also more widely spaced than those of purple loosestrife. Purple loosestrife 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
Purple loosestrife is endemic to the Old World, it was introduced to North America in the 1800's and for nearly a century it occurred as a pioneering species on the northeastern seaboard. About 60 years ago the range of purple loosestrife began rapidly expanding, reaching the upper midwest in the 1930's. The species appears to go through a period of acclimation after each range expansion during which the invasive character of the species is not expressed. It has only been within the last 10 years that purple loosestrife has been recognized as a serious threat to Illinois' wetlands. Purple loosestrife occurs most extensively in northern Illinois, though it is a threat throughout the state.

Habitat
Purple loosestrife occurs widely in wet habitats, such as marshes, bogs, pannes, fens, sedge meadows, and wet prairies, but it also occurs in roadside ditches, on river banks, and at the edges of reservoirs.

Life History
The reproductive capacity of purple loosestrife is one of the most significant and relevant life history characteristics of this herbaceous perennial plant. A single stalk can produce 300,000 seeds, and densities as high as 80,000 stalks/acre have been recorded, with the potential of producing as many as 24 billion seeds/acre. The seeds can remain viable even after 20 months of submergence in water. Seed set begins in mid to late July and continues through late summer. Seeds may be dispersed by water, wind and in mud attached to animals. Purple loosestrife also spreads vegetatively. Root or stem segments can form new flowering stems. Muskrat cuttings and mechanical clipping can also contribute to rapid spread by floating in riverine and lacustrine systems. Purple loosestrife lacks natural enemies in the United States.

Effects Upon Natural Areas
Purple loosestrife quickly crowds out most native vegetation in marsh, fen, sedge meadow, wet prairie, bog, and panne communities, creating a monoculture that provides little food or shelter for native wildlife. The natural character of several Illinois nature preserves is threatened by this exotic species.

CONTROL RECOMMENDATIONS

Research is currently being conducted into methods of biological control, and the U.S. Fish and Wildlife Service has begun a search for biological control agents that might be used against this species. However, only mechanical and chemical means of control are currently available. Current control methods have only limited success. The chances of success are best with the smallest infestations, and methods of control are determined by the size of the infestation. Early diagnosis is critical. Decisions on control methods must be balanced with the chances of success and the poten-tial damage caused by the treatment method.

RECOMMENDED PRACTICES IN NATURAL COMMUNITIES WITH NO KNOWN INVASION
Potential loosestrife habitat should be searched annually during late July and August for the plant. Early detection is the best approach!

RECOMMENDED PRACTICES IN NATURAL COMMUNITIES WITH INVASIONS
Effort in areas with individual plants and cluster of up to 100 plants Younger plants (1-2 years old) can be hand-pulled. Do not pull after flowering because this will scatter seed. Older plants, especially those in bogs or in deep organic soils, can be dug out. Roots of older plants can be "teased" loose with a hand cultivator. Bag and remove the plants from the site. Failure to place the removed plants in a bag could result in spread-ing the plant along your exit route because fragments may be dropped. Dispose of the plant by burning (preferable) or in an approved landfill. Follow-up treatments are recommended for three years after the plants are removed. Clothing, equipment and personnel should be cleaned to insure no seeds are spread on them, if seeds were present on plants.
If the above control method is not feasible in areas with relatively small infestations, spot application of glyphosate herbicides can be used as described below.

Effort in areas with clusters in excess of 100 plants (up to 4 acres in size)
Spot application of a glyphosate herbicide to individual purple loosestrife plants is the recommended treatment where hand pulling is not feasible. Glyphosate is available under the trade names Roundup and Rodeo, products manufactured by Monsanto. Only Rodeo is registered for use over open water. Herbicides only may be applied according to label directions and by licensed herbicide applicators or operators when working on publc properties. Glyphosate is nonselective so care should be taken not to let it come in contact with nontarget species. Glyphosate application is most effective when plants have just begun flowering. Timing is crucial, because seed set can occur if plants are in mid-late flower. Where feasible, the flower heads should be cut, bagged, and removed from the site before application to prevent seed set. Roundup should be applied by hand sprayer as a 1-1/2% solu-tion (2 oz. Roundup/gallon of clean water). Rodeo should also be applied as a 1-1/2% solution (2 oz. Rodeo/gallon clean water) with the addition of a wetting agent, as specified on the Rodeo label.
Another option is to apply glyphosate twice during the growing season. Foliage should be sprayed as described above, once when flowering has just started and a second time 2-3 weeks later. With this procedure control is likely more effective, because plants are not allowed to set seed and those missed because they were not flowering the first time are treated the second time.
Excessive application of herbicide (causing dripping from the plant) can kill desirable plants under the loosestrife. These plants, left unharmed, will be important in recolnizing the site after the loosestrife has been controlled. If the desirable plants are killed, the vigorously resprouting and growing purple loosestrife seeds present in the soil will fill the void. Since purple loosestrife is usually taller than the surround-ing vegetation, application to the tops of plants alone can be very effective and limit exposure of nontarget species. Complete coverage is not required to affect control.
The herbicide should be applied while backing away from treated areas to avoid walking through the wet herbicide. Equipment, clothing and personnel should be cleaned completely before entering other uninfested sensitive areas, if seeds were present in the treated area. It will be necessary to treat the same area again annually until missed plants and plants originating from the seed bank are eliminated.
Cutting purple loosestrife and subsequently flooding the area so that cut plant stalks are completely immersed has controlled purple loosestrife in at least one case. However, flooding may encourage the spread of purple loosestrife if seed are present in the soil. Artificial flooding should not be used in high-quality natural communities with an intact natural flooding regime.

Effort in areas with large monocultures (greater than 4 acres in size)
For large purple loosestrife populations, an assessment should be made to determine if the loosestrife can be eradicated with available resources. If it can not be controlled, then efforts should be placed on keeping the loosestrife out of the highest quality areas.
Applying glyphosate from a vehicle mounted sprayer is usually necessary in areas with extensive stands of purple loosestrife. The most effective control can be achieved by beginning treatment at the periphery of large patches and working towards the center in successive years. This allows peripheral native vegetation to reinvade the treated area as the loosestrife is eliminated.

FAILED OR INEFFECTIVE PRACTICES

Mowing, burning, and flooding have proven largely ineffective. A single known exception is cutting followed by flooding as described above. Mowing and flooding can actually contribute to further spread of the species by disseminating seed and cut plant stems. Do not mow because cut parts may re-root. No biological control methods that are feasible in natural areas are known.

REFERENCES

Bender, J. and J. Randall. 1987. Lythrum salicaria. The Nature Conservancy Element Stewardship Abstract. 8 pp.

Thompson, D.Q., R. L. Stuckey and E.B. Thompson. 1987. Spread, impact and control of purple loosestrife (Lythrum salicaria) in North American wetlands. Fish and Wildlife Research 2. 55 pp.

PERSONAL COMMUNICATION

Glass, William. 1988. Division of Natural Heritage, Illinois, Department of Conservation.

Laurie, Dennis. 1989. Lake County Forest Preserve District, Libertyville, Illinois.

Packard, Steve. 1989. The Nature Conservancy, Chicago, Illinois.

THISTLE, MUSK

Botanical: Carduus nutans
Family: N.O. Compositae

---Synonym---Nodding Thistle.
---Parts Used---Root, seeds.

Carduus nutans, the Musk Thistle, or Nodding Thistle, occurs in waste places, and is particularly partial to chalky and limestone soils. It is not uncommon in England, but is rare in Scotland, where it is confined to sandy seashores in the southern counties. The stem is erect, 2 to 3 feet high, branched only in larger plants, furrowed, interruptedly winged. The leaves are long, undulated, with scattered hairs on both surfaces, somewhat shiny, green and verydeeply cut. This is a common Thistle on a dry soil, and may be known by its large drooping, crimson-purple flowers, the largest of all our Thistle blooms, handsome both in form and colour, and by its faint, musky scent.

The down of this, as of some other species, may be advantageously used as a material in making paper.

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Last modified: 03/26/08