Invasive Weeds

This page is an ongoing project at Penn State in the Department of Plant Science to compile a comprehensive list of web information related to invasive weeds for the northeastern United States.

For Additions, deletions, or other information contact Dr. William S. Curran (


Government Sites

World, National and Canadian Sites

State and Regional Sites

University Sites

Private, Commercial and Non-profit Sites

On-line Books and Newsletters

Mail Order Books on Invasive and Noxious Weeds

  • Checklist Of The Woody Cultivated Plants Of Florida, By D. Burch, D.B. Ward, And D.W. Hall. 1988. Order From IFAS Publications, Ph.: 800-226-1764. Ask For SP-33.
  • A Great Lakes Wetland Flora, By S.W. Chadde. 1998. 569 Pp. Order From Pocketflora Press, Rr1 Box 206a, Calumet, Mi 49913; Ph.: 906-296-0506.
  • Invasive Species And Biodiversity Management, Edited By O.T. Sandlund, P.J. Schei And A. Viken. 1999. 431 Pp. Order From Kluwer Academic Publishers, 101 Philip Drive, Norwell, Ma 02061.
  • Alien Species In North America And Hawaii—Impacts On Natural Ecosystems, By G.W. Cox. 1999. 387 Pp. Order From Island Press, Pob 7, Covelo, Ca 95428; Ph.: 800-828-1302. E-Mail:
  • Hudson River Field Guide To Plants Of Freshwater Tidal Wetlands, By New York State Department Of Environmental Conservation, Illustrated By L.B. Mccloskey. 1998. 50 Pp. Order From Hudson River National Estuarine Research Reserve, C/O Bard College Field Station, Annandale, Ny 12504. Ph.: 914-758-7010.
  • Invasive Plants - Changing The Landscape Of America - Fact Book, By R.G. Westbrooks And The Federal Interagency Committee For The Management Of Noxious And Exotic Weeds. 1998. 107 Pp. Order From U.S. Department Of Agriculture, Natural Resources Conservation Service, Plant Materials Center, 14119 Broad Street, Brooksville, Fl 34601. Ph.: 352-796-9600.
  • Grasses, Sedges And Rushes Of Wetlands—With Notes About Wildlife Use, By V. Ramey, Photos And Illustrations By A. Murray. University Of Florida, Center For Aquatic And Invasive Plants. 1999. 184 Pp. Order From Ifas Publications, Pob 110011, Gainesville, Fl 32611-0011. Ph.:352-392-1764; 800-226-1764.
  • Identification And Biology Of Non-Native Plants In Florida’s Natural Areas, Edited By K.A. Langeland And K. Craddock Burks. University Of Florida. 1999. 165 Pp. Order From Ifas Publications, Pob 110011, Gainesville, Fl 32611; Ph.: 800-226-1764.
  • Invasive Plants—Weeds Of The Global Garden, Edited By J.M. Randall And J. Marinelli. Brooklyn Botanic Garden, Handbook #149. 1996. 111 Pp. Order From Brooklyn Botanic Garden, 1000 Washington Ave, Brooklyn, Ny 11225-2097. Ph.:718-622-4433, Ext. 274.
  • Significant Habitats And Habitat Complexes Of The New York Bight Watershed, By The U.S. Fish And Wildlife Service, Southern New England-New York Bight Coastal Ecosystems Program. 1997. CD-Rom. E-Mail: R5es_Snenybcep@Mail.Fws.Gov.
  • Introduction Of Non-Native Plants Into The Natural Environment, By J. Lambinon. 1997. 29 Pp. Order From The Council Of Europe Publishing, Council Of Europe, F-67075 Strasbourg Cedex, Nature And Environment Series No. 87. E-Mail: Cd.Publishing@Seddoc.Coe.Fr.
  • Control Of Non-Native Plants In Natural Areas Of Florida, By K.A. Langeland And R.K. Stocker. 1997. 38 Pp. Order From Ifas Publications, Pob 110011, Gainesville, Fl 32611-0011, Ph.: 800-226-1764.
  • Through The Looking Glass… A Field Guide To Aquatic Plants, By S. Borman, R. Korth, And J. Temte. 1997. 248 Pp. Order From Nalms Bookstore, Pob 5443, Madison, Wi 53705-5443. Ph.: 608-223-2836.
  • Common Flora Of The Playa Lakes, By D.A. Haukos And L.M. Smith. 1997. 196 Pp. Order From Texas Tech University Press, Box 41037, Lubbock, TX 79409-1037. Ph.: 800-832-4042. E-Mail:
  • Notes On Florida’s Endangered And Threatened Plants, By N.C. Coile. 1998. 119 Pp. Order From Division Of Plant Industry (Dpi), Florida Department Of Agriculture And Consumer Services, Pob 147100, Gainesville, Fl 32614-7100. Contribution No. 38, 2nd Edition.
  • Aquatic And Wetland Plants Of Northeastern North America, By G.E. Crow And C.B. Hellquist. 1999. For A Pre-Publication Discount, And For More Information, Contact Mr. Steve Salemson, Associate Director, The University Of Wisconsin Press, 2537 Daniels Street, Madison, Wi 53718-6772. Ph.: 608-224-3889, Fax: 608-224-3924.E-Mail:
  • Biological Control Of Weeds—Proceedings Of The Viii International Symposium On Biological Control Of Weeds, 2-7 February, Canterbury, New Zealand, Edited By E.S. Delfosse And R.R. Scott. 1996. 760 Pp. Order From Csiro Publishing, Pob 1139, Collingwood 3066, Victoria, Australia. (+61)-3-9662-7666. E-Mail: Sales@Publish.Csiro.Au.
  • Strangers In Paradise—Impact And Management Of Nonindigenous Species In Florida, Edited By D. Simberloff, D.C. Schmitz And T.C. Brown. 1997. 467 Pp. Order From Island Press, Box 7, Dept. 2pr, Covelo, Ca 95428. Ph.: 800-828-1302.
  • Proceedings Of The Ix International Symposium On Biological Control Of Weeds, Edited By V.C. Moran And J.H. Hoffmann. 1996. 563 Pp. Order From J.H. Hoffmann, Zoology Department, University Of Cape Town, Rondebosch 7700, South Africa.E-Mail: Hoff@Botzoo.Uct.Ac.Za.
  • Managing Aquatic Vegetation With Grass Carp—A Guide For Water Resource Managers, Edited By John R. Cassani. 1996. 196 Pp. Order From American Fisheries Society, Publication Fulfillment, Pob 1020, Sewickley, Pa 15143. Ph.: 412-741-5700; Fax: 412-741-0609.
  • Grow Your Own Native Landscape: A Guide To Identifying, Propagating, And Landscaping With Western Washington Native Plants, Edited By Michael Leigh. 1996. 132 Pp. Order From WSU Cooperative Extension, Thurston County, Native Plant Salvage Project, 6128 Capitol Blvd. S.E., Suite 3, Olympia, WA 98501; Ph.: 360- 786-5445.
  • Restoring Prairie Wetlands—An Ecological Approach, By Susan M. Galatowitsch And Arnold G. Van Der Valk. 1994. 246 Pp. Order From Iowa State University Press, 2121 S. State Avenue, Ames, Iowa 50014-8300; Ph.: 800-862-6657.
  • Dictionary Of Plant Names, In Latin, German, English And French, By H. Nikolov. 1996. 926 Pp. ISBN 3-443-50019-6 Order From J. Cramer, Gebruder Borntraeger, Johannesstr. 3a, D-70176 Stuttgart, Germany. Tel: 0711/625001.
  • Wildlife Community Habitat Evaluation: A Model For Deciduous Palustrine Forested Wetlands In Maryland - Final Report, By R.L. Schroeder. 1996. 42 Pp. Order From National Technical Information Service, 5285 Port Royal Road, Springfield, VA 22161. Technical Report Wrp-De-14. Final Report From The Us National Biological Service To The Us Army Corps Of Engineers.
  • Water Gardening—Water Lilies And Lotuses, By P.D. Slocum, And P. Robinson, With F. Perry. 1996. 434 Pp. ISBN 0-88192-335-4. Order From Timber Press, Inc., 133 SW Second Avenue, Suite 450, Portland, Or 97204-3527, Ph.: 800-327-5680.

On-line Fact Sheets

Fact Sheets for Problem Invasive Weeds

The following links represent those plant species considered non-native to North America and accepted by researchers, scientists, botanists and ecologists as invasive by nature. These plants are all non-native ornamentals that are planted for their beautification, medicinal, or conservation attributes. They are considered invasive because they are known to dominate a landscape and crowd out native vegetation. If they escape, their invasive growth habit often leads to detrimental economic and ecological impacts within a native plant community. Several species on this list have little or no invasive information available. Several species are widely accepted as beneficial and the web links reflect research promoting selected species based on their beneficial invasive characteristics.

Non Native Trees (Norway maple, tree of heaven, autumn olive, princess tree, bradford callery pear, white mulberry)

Norway maple (Acer platanoides)

This beautiful crimson colored tree is planted all over the United States for its beautiful fall foliage. However, due to its prolific seed production, this tree has migrated into forested areas and is rapidly displacing native maples and other native hardwood trees.

Tree of heaven (Ailanthus altissima)

This herbaceous woody plant was introduced into the Philadelphia area more than a 100 years ago as an attractive ornamental addition to a private garden. It has since naturalized and become a nuisance plant along roadsides throughout the East Coast.

Autumn olive (Elaeagnus umbellata); Russian olive (Elaeagnus angustifolia)

Autumn olive is a deciduous shrub or small tree in the Oleaster family. Autumn olive was introduced to the United States from East Asia in the 1830’s.

Princess tree (Paulownia tomentosa)

Princess tree, also known as royal paulownia or empress tree, is a small to medium sized tree in the figwort family.

Bradford Callery Pear (Pyrus calleryana)

P. calleryana is a blight resistant variety that has been bred into fruiting varieties. A variety, named Bradford, is a beautiful tree that is grown for ornament and reaches a height ranging from 30 to 50 feet.

White mulberry (Morus alba)

The white mulberry is native to eastern and central China. It became naturalized in Europe centuries ago. The tree was introduced into America for silkworm culture in early colonial times and naturalized and hybridized with the native red mulberry.

Non Native Shrubs and Semi-Woody Perennials (Japanese barberry, Japanese and giant knotweed, Japanese and exotic bush honeysuckle, privets, and buckhorn species)

Japanese barberry (Berberis thunbergii)

Japanese barberry was introduced from Japan around 1875. It is commonly planted for ornamental reasons (its scarlet fruit and autumnal foliage in shades of orange, red, and crimson make it an attractive hedge), as well as for wildlife and erosion control.

Multiflora Rose (Rosa multiflora)

Multiflora rose is a thorned bramble perennial plant that now infests more than 45 million acres throughout the eastern half of the United States.

Japanese Knotweed (Polygonum cuspidatum)

Japanese knotweed is a semi-woody perennial. It has been cultivated commonly because of its interesting, fast-growing and hollow, bamboo-like stems that form dense leafy thickets, 1-3 m tall, and its late summer flower clusters.

Giant knotweed (Polygonum sachalinense)

Sakhalin knotweed is 3 to 4 m tall and closely related to Japanese knotweed. Plants appear to have allelopathic properties. Introduced from mountains of Japan and Sakhalin Islands.

Japanese Honeysuckle (Lonicera japonica)

Lonicera japonica is a perennial trailing or climbing woody vine of the honeysuckle family (Caprifoliaceae) that spreads by seeds, underground rhizomes, and aboveground runners (USDA 1971).

Exotic bush honeysuckle (Lonicera tartarica, L. x bella, L. maackii, L. morrowii)

Exotic bush honeysuckles are upright, multi-stemmed, oppositely branched, deciduous shrubs that range in height from 2 m to 6 m. The opposite leaves are simple and entire, and paired, axillary flowers are showy with white, pink, or yellow corollas. The fruits of Lonicera spp. are red, or rarely yellow, fleshy berries (Gleason and Cronquist 1991). In flower, exotic bush honeysuckles can be distinguished from all native bush honeysuckles except swamp fly-honeysuckle (L. oblongifolia) by their hirsute (hairy) styles.

Exotic privets (Ligustrum sinense)

A member of the olive family (Oleaceae), Chinese privet is a shrub which can grow to twelve feet in height.

Common buckthorn and glossy buckthorn (Rhamnus sp.)

Common buckthorn is a deciduous perennial shrub or small tree that reaches up to 20 feet in height.

Non Native Vines (akebia, porcelain berry, Asiatic bittersweet, Chinese yam, wintercreeper, winged Euonymus, Japanese hops, English ivy, mile a minute, kudzu)

Five-leaf akebia (Akebia quinata)

The species is a vigorous deciduous vine with 5-leaflet compound foliage, purple flowers and fruit introduced from eastern Asia by Fortune in 1845.

Porcelainberry (Ampelopis brevipedunculata)

This vine has escaped from gardens and can be found choking out roadside vegetation, forested understories and even buildings.

Asiatic bittersweet (Celastrus orbiculatus)

This vine is an invasive, non-native woody vine. It is particularly troublesome in natural areas.

Chinese yam (Dioscorea batatas)

Herbaceous or slightly woody twining vines with fleshy or woody rootstocks, winding upward from left to right to approximately 13 feet in length. Found especially throughout the piedmont and mountainous areas of Virginia, Georgia, and West Virginia.

Wintercreeper (Euonymus fortunei)

Climbing euonymus, also known as wintercreeper, Emerald’n Gold, and Gaiety, is an evergreen, clinging vine in the staff-tree (Celastraceae) family.

Winged Euonymus (Euonymus alatus)

The winged spindle tree is a dense, flat-topped shrub or small tree usually broader than high, with stiff, horizontally spreading branches. The bark of young twigs is broken into four thin, blade-like corky ridges. Native to northeast Asia.

Japanese hops, (Humulus japonicus)

Japanese hops are aggressive vining plants with 5-lobed leaves and stems with prickles.

English ivy, (Hedera helix)

English ivy has left the residences and is invading the forests — it is out of control.

Mile-A-Minute (Polygonum perfoliatum)

Mile-a-minute is an introduced weed from eastern Asia that is rapidly colonizing non-crop areas in Pennsylvania and surrounding states.

Kudzu (Pueraria lobata)

Kudzu, native to eastern Asia, was introduced into the eastern and southern United States in the 1800s. It was originally promoted for erosion control and as an inexpensive forage for livestock. It is now present from Florida to New York, westward to central Oklahoma and Texas, with heavy infestations in Alabama, Georgia and Mississippi. Kudzu resembles a giant bean stalk.

Misc. Non Native Herbaceous Dicots (garlic mustard, black swallow-wort, spotted knapweed, Canada thistle, poison hemlock, lespedeza, Dame's rocket, Eurasian water-milfoil, purple loosestrife, star of Bethlehem, Japanese spiraea, wineberry, periwinkle, stinging nettle, lesser celandine)

Garlic mustard (Alliaria petiolata)

This low growing perennial in the mustard family has spread like quick silver across the Northeast and is dramatically establishing itself in every known landscape. It is especially detrimental to forest understory vegetation as it is smothering out sensitive ecologically endangered native plants.

Black swallow-wort or dog-strangling vine (Vincetoxicum spp.); (Cynanchum spp.)

Found in the U.S. (northeast and midwest areas) and in Canada, these perennial herbs die back to the crown each year and are native to southwestern Europe.

Spotted knapweed (Centaurea maculosa)

This aggressive, perennial is undesirable to herbivores and is taking over pastures, greens and roadside areas all across the United States.

Canada thistle (Cirsium arvense)

Canada thistle is an aggressive, creeping perennial weed that infests crops, pastures, rangeland, roadsides and noncrop areas.

Poison hemlock (Conium maculatum)

Poison hemlock is a highly toxic weed found in waste places throughout much the world.

Sericea lespedeza (Lespedeza cuneata)

A perennial with erect stems that may reach 5 feet in height. Sericea lespedeza is often a weed of pastures, hay fields, roadsides, and abandoned fields. It is found throughout the southeastern United States.

Dame’s rocket (Hesperis matronalis)

An upright, hardy perennial native to Europe, but has escaped cultivation and adapted throughout most of the United States. Delightful lilac-purple flowers are concentrated at the end of sturdy stalks.

Eurasian water-milfoil (Myriophyllum spicatum)

Eurasian water-milfoil is a perennial, aquatic, submersed herb that was accidentally introduced from Eurasia, probably in the 1940’s.

Purple loosestrife (Lythrum salicaria)

A plant of European origin, has spread and degraded temperate North American wetlands since the early nineteenth century. The plant was introduced both as a contaminant of European ship ballast and as medicinal herb for treatment of diarrhea, dysentery, bleeding, wounds, ulcers and sores.

Star of Bethlehem (Ornithogalum umbellate)

This member of the Lily family has an onion-like bulb.

Japanese spiraea (Spiraea japonic)

Japanese spiraea, also called Japanese meadowsweet, is a perennial, deciduous shrub in the rose family (Rosaceae), that grows to 4 or sometimes 6 feet in height and about the same in width.

Wineberry (Rubus phoenicolasius)

Wineberry is grown for its ornamental foliage which has silvery under-surfaces and purplish veins.

Periwinkle (Vinca major) and (Vinca minor)

The well-known Periwinkles—both Greater and Lesser—familiar plants of our woods and gardens, are members of the genus Vinca, so named by Linnaeus, which includes five in Europe, and the Orient, and three species native to the East Indies, Madagascar and America, assigned by a later botanist, Reichberg, to a separate genus, Lochnera, as they differ from Vinca in the stamens and head of the style not being hairy, though the main characteristics are the same.

Stinging nettle (Urtica dioica)

Stinging Nettles are perennials that belong in the nettle family Urticaceae and have opposite leaves.

Lesser celandine (Ranunculus ficaria)

Lesser celandine is a perennial herbaceous plant in the buttercup family (Ranunculaceae), with shiny dark green leaves arranged in a low-growing, loose rosette.

Non Native Monocots (Chinese silvergrass, Reed canarygrass, Japanese stiltgrass, Bermudagrass, phragmites)

Chinese silvergrass (Miscanthus sinensis Anderss.)

A native plant in Polynesia and Micronesia; should not be introduced to habitats where it is not already present, especially those subject to fire.

Reed Canary Grass (Phalaris arundinacea)

Reed canary grass is highly tolerant to flooding, resistant to burning, and quickly forms virtual monocultures by shading native grasses and forbs with its dense growth and litter production. It is a prolific seed producer and spreads through rhizome growth at an amazing rate. Wet meadow restoration is hampered because reed canary grass takes over the wet meadow zone when wetland hydrology is restored. Native wet meadow plants have difficulty becoming established unless drastic and expensive management is applied.

Japanese stiltgrass, (Microstegium vimineum)

An alien invader is spreading like wildfire through the parklands of Maryland and Virginia. Japanese stiltgrass is a dense, mat-forming annual grass that roots at nodes, is shade tolerant, and occupies various habitats including creek banks, floodplains, forest roadsides and trails, damp fields, and swamps. It is very aggressively displacing our native plants.

Bermudagrass (Cynodon dactylon)

This grass can be an invasive and competitive weed. The extensive stolon and rhizome system provide a means of rapid expansion. However, this species, which requires high temperatures and high light levels to thrive, grows only in disturbed areas.

Phragmites (Phragmites australis)

This perennial wetland grass known as common reed, has become a serious pest. It’s an aggressive invader of wetlands, producing nearly impenetrable stands of reeds up to 12 feet tall. Beneficial wetland plants are displaced by the Phragmites, which provides little food or shelter value to wildlife.