This list is retained for historical interest only. Please refer to the list of Non-native Invasive and Potentially Invasive Vascular Plants in Connecticut maintained by the Connecticut Invasive Plant Working Group for current information.

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This is a list of vascular plant species which are invasive into "natural areas". Many of the species on this list also occur in disturbed areas and have the potential of invading nearby natural habitats. Most species included in the Main List are not native to Connecticut. The list does not include many of the long established non-native species that have been used as ornamentals or as crops or forage plants and can dominate small or large tracts of anthropogenic landscapes such as lawns and abandoned agricultural lands.

A "natural area", as it is used here, is hard to define. I do not mean sites officially designated as natural areas. Rather, I mean sites where recent human impacts are either minimal or if humans have managed the site it has been done for conservation reasons. I include in my loose definition sites for rare or imperiled species, conservation lands managed to preserve biological diversity, small or large undisturbed parcels that, for the most part, are natural or have not recently been impacted by humans. Natural disturbance is frequently a component of the system. I do not mean agricultural lands, gardens, roadsides, or other human-controlled landscapes. I have not listed agricultural or garden weeds or other so-called noxious weeds.

Appendix 1 includes species which, although locally abundant and spreading, do not usually disperse far from the original site of intentional introduction. Appendix 2 includes species that are native to some part of Connecticut but have either extralimital occurrences that are probably anthropogenic or non-indigenous genotypes. Appendix 3 and Appendix 4 are Watch Lists. Appendix 3 includes taxa about which there are questions. Some species included in Appendix 3 are present in the State but, in spite of their aggressively invasive nature elsewhere, do not seem to be invasive here at this point in time. Others are widespread in Connecticut but appear not to be invasive into natural habitats. Appendix 4 includes invasive taxa that are not yet documented from Connecticut but are reported from nearby states. These can be anticipated in Connecticut.

Taxa are arranged alphabetically by family, and within a family by Genus and species. Annotations with each entry may include the area to which the taxon is thought to be native, comments on its distribution, abundance, and dispersal in Connecticut, and year of earliest Connecticut specimen. The number following the "G&C-" refers to the page in Gleason and Cronquist's 2d edition (Gleason, H.A. and A. Cronquist. 1991. Manual of the Vascular Plants of Northeastern United States and Adjacent Canada 2d edition. New York Botanical Garden, Bronx, NY) where a description of the taxon can be found. Dates of earliest record from Connecticut are based on herbarium specimens. * = native to Connecticut.

This list is meant to be dynamic. Species will be added, deleted, or moved based upon additional data and comments from reviewers. Records for all species included here are from herbarium specimens. Additional records and specimens should be sent to the George Safford Torrey Herbarium. Reports of species included in Appendix 3 that are aggressively invading undisturbed habitats are needed to improve the list. Likewise, reports are sought of species included in Appendix 1 aggressively invading natural habitats that are well removed from and discontinuous with the site of original intentional introduction. Occurrences of species from Appendix 4 should be reported immediately.

This list will be reissued semiannually, in October and April.

Acknowledgements

I want to thank the following people for their helpful comments: Margaret Ardwin, Joe Dowhan, Glenn Dryer, Donna Ellis, Elizabeth Farnsworth, Dick Goodwin, Joyce Hemingson, Don Les, Chris Mangels, Mark McDonnell, Noble Proctor, and other field botanists who have answered questions over many years or commented on previous iterations of this list. The final choices, good or bad, have been mine. No one else should be held accountable.

Summary of Main List and Appendices

Please send comments, questions, and specimens to:

Leslie J. Mehrhoff, Curator

George Safford Torrey Herbarium

Department of Ecology and Evolutionary Biology

Box U-42, 75 North Eagleville Road

University of Connecticut

Storrs, CT 06269-3042

telephone: 860-486-1889 fax: 860-486-6364

e-mail: vasculum@uconnvm.uconn.edu

Main List

Amaranthaceae

Froelichia gracilis (Hook.) Moq.

Cottonweed

Southwestern U.S.; sporadic along major highways; 1973; G&C-109.

Apiaceae

Aegopodium podagraria L.

Goutweed

Eurasia; invasive along streams; commonly planted and escaping from cultivation; G&C-371.

Asclepiadaceae

Vincetoxicum nigrum (L.) Moench.

Black Swallow-wort

Europe; widespread and and increasingly common; wind dispersed; 1901; G&C-399.

Vincetoxicum rossicum (Kleo.) Barb.

Swallow-wort

Europe; overlooked until recently, this species is common along coast and sporadic inland; wind dispersed; 1881; not in G&C.

Asteraceae

Centaurea maculosa Lam.

Spotted Knapweed

Europe; widespread along roadsides and disturbed areas, potentially a problem in early succussional habitats; G&C-615.

Berberidaceae

Berberis thunbergiiDC.

Japanese Barberry

Japan; widespread and common, can form large monotypic stands in forest understory; bird dispersed; G&C-64.

Bignoniaceae

Paulownia tomentosa (Thunb.) Steudel

Empress-tree

China; commonly planted near coast, especially around old ports, seedlings and saplings common, especially in coastal New London and Fairfield Counties; G&C-493.

Brassicacaeae

Alliaria petiolata (Bieb.) Cavara & Grande

Garlic Mustard

Eurasia; widespread and extensive in central and western Connecticut, becoming more so east of the Connecticut River; G&C-197.

Cardamine impatiens L.

Europe; common in western Connecticut and in the Connecticut River Valley, sporadic in eastern Connecticut; often overlooked; G&C-190.

Hesperis matronalis L.

Dame's Rocket

Eurasia; increasingly common in rich soils across Connecticut; garden escape; G&C-196.

Lepidium latifolium L.

Tall Pepperwort

Southern Europe and western Asia; dense stands occur along the coast and on coastal islands in Fairfield County, it has recently been found along the Mass. Turnpike near I-84 and northeastern Connecticut; G&C-181.

Nasturtium officinale R. Br.

Watercress

Syn. Rorippa nasturtium-aquaticum (L.) Hayck.

Eurasia; sporadic across Connecticut in clear, quiet watercourses; possibly intentionally introduced and escaped from cultivation; G&C-193.

Cabombaceae

Cabomba caroliniana A. Gray

Fanwort

Midwestern USA, probably not native here; common in eastern Connecticut; often dispersed by boats and boat trailers or aquarium enthusiasts; 1937; G&C-46.

Callitrichaceae

Callitriche stagnalis Scop.

Europe; not known in Connecticut until recently; it appears to be invasive in streams and slow-moving rivers in western Connecticut, its current distribution and status elsewhere in Connecticut are unclear; 1993. G&C-459.

Caprifoliaceae

Lonicera japonica Thunb.

Japanese Honeysuckle

Eastern Asia; widespread and common in Connecticut, especially near the coast; escaped from cultivation; dispersed by birds; G&C-509.

Lonicera maackii (Rupr.) Maxim.

Amur Honeysuckle

Asia; sporadic in Connecticut; escaped from cultivation; dispersed by birds; G&C-509.

Lonicera morrowii A. Gray

Morrow's Honeysuckle

Japan; probably widespread but sproradic; escaped from cultivation; dispersed birds; G&C-509.

Lonicera tatarica L.

Tatarian Honeysuckle

Eurasia; commonly planted and probably sproradic as an escape from cultivation; dispersed by birds; G&C-509.

Lonicera xylosteum L.

European Fly-honeysuckle

Europe; Connecticut status in the wild unclear, probably sporadic; escaped from cultivation; dispersed by birds; G&C-509.

Lonicera x bellaZabel

Bella Honeysuckle

Hybrid of L. tatarica and L. morrowii; well established and widespread; escaped from cultivation; dispersed by birds; G&C-509.

Viburnum sieboldii Miq.

Japan; sporadic in woodlands and apparently increasing; probably dispersed by birds; G&C-512.

Celastraceae

Celastrus orbiculatus Thunb.

Asiatic Bittersweet

Eastern Asia; widespread and very common, probably in every town in Connecticut; escaped from cultivation; dispersed by birds; G&C-328.

Euonymus alatus (Thunb.) Sieb.

Winged Euonymus

Eastern Asia; widespread and becoming increasingly common; escaped from cultivation; dispersed by birds; G&C-329.

Chenopodiaceae

Kochia scoparia (L.) Schrader

Summer Cypress

Europe; common along the coast at the upper edges of salt marshes; maybe dispersed inland in bird seed mixes; G&C-99.

Elaeagnaceae

Elaeagnus umbellata Thunb.

Autumn Olive

Eastern Asia; widespread and very common, probably in every town in Connecticut; escaped from cultivation as wildlife food and for rapid establishment against erosion; dispersed by birds; G&C-307.

Fabaceae

Amorpha fruticosa

Southern and midwestern USA; common along major rivers in Connecticut. G&C-300.

Pueraria lobata (Willd.) Owhi

Kudzu-vine

Japan; uncommon along coast, currently unknown inland in Connecticut; climbing on and over nearby vegetation, first Connecticut record 1928; at least one current population appears to be vegetative. C&G-305.

Geraniaceae

Geranium nepalense Sweet

Nepalese Crane's-bill

Eastern Asia; local in Litchfield County; amazingly aggressive, highly competitive even with lawn grasses; 1981; G&C-360.

Haloragaceae

Myriophyllum spicatum L.

European Water-milfoil

Europe; apparently increasing across the state as it is moved about by boats and boat trailers; 1979; G&C-308.

Hydrocharitaceae

Egeria densa Planchon

Brazilian Water-weed

Southeastern Brazil to northern Argentina; apparently increasing in ponds in southern Connecticut; it is commonly encountered as a plant used in aquaria and aquatic gardens and has probably accidentally escaped and become established; 1992; G&C-637.

Hydrilla verticillata (L. f.) Royle

Hydrilla

"Old World"; currently known from only two ponds in the state, both in southeastern Connecticut, where it is amazingly aggressive; potentially a serious problem in any body of freshwater; dispersed by birds and boats; First Connecticut record - 1989; G&C-637.

Iridaceae

Iris pseudacorus L.

Yellow Iris

Europe; widespead and becoming increasingly common; escaped from cultivation; G&C-848.

Lamiaceae

Elsholtzia ciliata (Thunb.) Hylander

Elsholtzia

Asia; sporadic, first Connecticut record - 1990; G&C-447.

Liliaceae

Allium vineale L.

Wild Garlic

Europe; widespread and common, especially in open fields and meadows, increasingly common in rich woodlands; dispersed by vegetative propagules; G&C-832.

Lythraceae

Lythrum salicaria L.

Purple Loosestrife

;Eurasia; widespread and common, one of our most visible invasive species when it dominates large parts of entire wetland systems; reproduces by seeds and vegetative propagules; a serious problem; G&C-311.

Oleaceae

Ligustrum vulgare L.

European Privet

Europe; widespread and sporadic, becoming increasingly common in natural areas, other Ligustrum species may be involved and worthy of consideration: primarily dispersed by birds; G&C-463.

Poaceae

Bromus tectorum L.

Drooping Brome-grass

Europe; widespread in Connecticut but mostly in disturbed sites, sporadic in sand plain communities; G&C-773.

Microstegium vimineum (Trin.) A. Camus

Japanese Stilt Grass

Tropical Asia; occasional and sporadic, mostly in southern parts of state, very likely to increase aggressively; first Connecticut report 1990 reported in 1980s; a serious problem in New Jersey and Pennsylvania; G&C-815.

Phragmites australis (Cav.) Trin.

Common Reed

Cosmopolitan; widespread, very common, and very aggressive; G&C-781.

Poa compressa L.

Canada Bluegrass

Europe; widespread and very common in open dry sandy soils and rocky woods and ledges; G&C-754.

Polygonaceae

Polygonum cuspidatum Sieb. & Zucc.

Japanese Knotweed

Japan; widespread and very common, often occurs in areas of natural disturbance such as river or pond shores; escaped from cultivation; G&C-139.

Rumex acetosella L.

Red sorrel

Eurasia; widespread and very common; frequently occurs on balds and rocky outcrops; G&C-130.

Potamogetonaceae

Potamogeton crispus L.

Europe; increasingly common in Connecticut, probably primarily dispersed by boats and boat trailers; 1908; G&C-642.

Ranunculaceae

Ranunculus ficaria L.

Lesser Celandine

;Eurasia; sporadic in southern Connecticut in rich woodlands and flood plain forests; G&C-59.

Rhamnaceae

Frangula alnus Mill.

European Buckthorn

Syn. Rhamnus frangula L.

Eurasia; widespread and very common, its wide ecological amplitude has allowed it to become established in a variety of habitats from wetland to upland woods and fields; escaped from cultivation, dispersed by birds; G&C-341.

Rhamnus cathartica L.

Buckthorn

Eurasia; widespread but sporadic, frequent in northwestern Connecticut; escaped from cultivation; G&C-342.

Rosaceae

Rosa multiflora Thunb.

Multiflora Rose

Eastern Asia; widespread, very common, and aggressively spreading, usually encountered in open areas, it can be found in woodlands where it tenaciously persists; escaped from cultivation where it was used as a bank stabilizer and as a wildlife food; G&C-257.

Rubus phoenicolasias Maxim.

Wineberry

Eastern Asia; widespread and common along the coast, sporadic but increasing inland; escaped from cultivation, its berries are attractive and delicious; G&C-251.

Simaroubaceae

Ailanthus altissima (Mill.) Swingle

Tree-of-heaven

Eastern Asia; widespread and common, especially near urban areas and along coast; escaped from cultivation; G&C-354.

Solanaceae

Solanum dulcamara L.

Climbing Nightshade

Eurasia; widespread and very common in a wide variety of habitats; probably bird dispersed but there is a paucity of reports of birds feeding on fruits; G&C-404.

Vitaceae

Ampelopsis brevipedunculata (Maxim.)

Chinaberry, Heartleaf Ampelopsis

Northeast Asia; widespread but sporadic, more commonly encountered near the coast; escaped from cultivation; G&C-343.

Appendix 1

Seemingly invasive non-native species that usually do not disperse far from site of original intentional introduction. Many grasses used as forage crops might be included here.

Apocynaceae

Vinca minorL.

Common Periwinkle

Southern Europe; G&C-393.

Araliaceae

Hedera helix L.

English Ivy

Europe; G&C-364.

Buxaceae

Pachysandra terminalis Siebold & Zucc.

Pachysandra

Japan; G&C-332.

Celastraceae

Euonymus fortunei Hand.-Mazz.

Climbing Euonymus

China; not in G&C.

Fabaceae

Coronilla varia L.

Crown-vetch

Europe; G&C-286.

Cytisus scoparius (L.) Link

Scotch Broom

Europe; G&C-277.

Lespedeza cuneata (Dum. Cours.) G. Don

Chinese Lespedeza

Eastern Asia; G&C-298.

Lardizabalaceae

Akebia quinata Dcne.

Akebia

Eastern Asia; G&C-65.

Liliaceae

Hemerocallis fulva L.

Orange Day-lily

Eurasia; G&C-830.

Ranunculaceae

Clematis terniflora DC.

Yam-leaved Clematis

Japan; G&C-54.

Rosaceae

Rosa rugosa Thunb.

Japanese Rose

Eastern Asia; G&C-257.

Sorbaria sorbifolia

Eastern Asia; G&C-241.

Appendix 2

Native or potentially native species that may have some populations that are non-indigenous and invasive.

Aceraceae

Acer negundo L.

Box-elder

G&C-353.

Asteraceae

Xanthium strumarium L.

Common Cocklebur

G&C-550.

Berberidaceae

Podophyllum peltatum L.

May-apple

G&C-63.

Haloragaceae

Myriophyllum heterophyllum Michx.

G&C-309.

Poaceae

Phalaris arundinacea L.

Reed Canary-grass

G&C-765.

Appendix 3 -- Watch List; Questionable Problems

Taxa reported from Connecticut but that do not appear to be invasive at this time, however, these taxa are acknowledged problems as invasive aliens in nearby states or similar habitats. Aggressive invasiveness into "natural" habitats may be questionable. Please report any sites where these species appear to be aggressively invading natural habitats.

Aceraceae

Acer platanoides L.

Norway Maple

Europe; G&C-352.

Acer pseudoplatanus L.

Sycamore Maple

Europe; G&C-352.

Araliaceae

Aralia elata

Northeastern Asia; not in G&C.

Aralia spinosa

Southeastern USA; G&C-363.

Asteraceae

Carduus nutans L.

Musk-thistle

Europe; G&C-610.

Cirsium arvense (L.) Scop.

Canada-thistle

Eurasia; G&C-613.

Cirsium vulgare(Savi) Tenore

Bull-thistle

Eurasia; G&C-613.

Tussalago farfara

Eurasia; G&C-560.

Berberidaceae

Berberis vulgaris L.

Barberry

Europe; G&C-64.

Betulaceae

Alnus glutinosa (L.) Gaertner

Black Alder

Eurasia and North Africa; not in G&C.

Boraginaceae

Myosotis scorpioides L.

Forget-me-not.

Europe; G&C-422.

Butomaceae

Butomus umbellatus L.

Flowering Rush

Eurasia; G&C-632.

Cannabaceae

Humulus japonicusSieb. & Zucc.

Japanese Hops

Eastern Asia; G&C-73.

Caprifoliaceae

Viburnum plicatum Thunb.

Eastern Asia; G&C-514.

Chenopodiaceae

Cycloloma atriplicifolium (Spreng.) Coult.

Winged Pigweed

Midwestern USA; G&C-99.

Elaeagnaceae

Elaeagnus angustifolia L.

Russian Olive

Eurasia; G&C-307.

Euphorbiaceae

Euphorbia cyparissias L.

Cypress Spurge

Eurasia; G&C-338.

Euphorbia esula L.

Leafy Spurge

Eurasia; G&C-338.

Fabaceae

Robinia pseudoacacia L.

Black Locust

Southeastern USA; G&C-280.

Fumariaceae

Fumaria officinalis L.

Fumitory

Europe; G&C-70.

Grossulariaceae

Ribes sativum Syme

Garden Red Currant

Eurasia; G&C-228.

Haloragaceae

Myriophyllum aquaticum (Vell.) Verdc.

Parrotfeather

South America; G&C-308.

Lamiaceae

Ajuga reptans L.

Carpet-bugle

Eurasia; C&G-434

Liliaceae

Ornithogalum umbellatum L.

Star of Bethlehem

Europe; G&C-829.

Marsileaceae

Marsilea quadrifolia L.

Water Shamrock

Europe; G&C-30.

Moraceae

Morus alba L.

White Mulberry

Eastern Asia; G&C-75.

Najadaceae

Najas minor Allioni

European Water-nymph, Spiny Naiad

Old World; G&C-646.

Nyctaginaceae

Mirabilis nyctaginea (Michx.) MacM.

Heart-leaved Umbrella-wort

Western USA; G&C-93.

Onagraceae

Epilobium hirsutum L.

Hairy Willow-herb

Eurasia and northern Africa; G&C-316.

Poaceae

Aira caryophyllea L.

Silver Hairgrass

Europe; G&C-764.

Polygonaceae

Polygonum cespitosum Blume

Eastern Asia; G&C-137.

Primulaceae

Lysimachia vulgaris L.

Garden Loosestrife

Eurasia; G&C-222.

Rubiaceae

Galium mollugo L.

Wild Madder

Eurasia; G&C-505.

Rutaceae

Phellodendron japonicum Maxim.

Cork-tree

Japan; G&C-356.

Salicaceae

Populus alba L.

White Poplar

Eurasia; G&C-167.

Solanaceae

Datura stramonium L.

Jimsonweed

Asia; C&G-406.

Taxaceae

Taxus cuspidata Sieb. & Zucc.

Japanese Yew

Japan, eastern Asia; G&C-32.

Valerianaceae

Valeriana officinalis L.

Garden Heliotrope

Eurasia; G&C-516.

Appendix 4 -- Watch List; Anticipated Problems

Taxa not currently known to exist in Connecticut but might be anticipated because of populations nearby in adjacent states. In addition, any taxon included here is known to be invasive in similar habitats in other states.

Asteraceae

Cirsium palustre (L.) Scop.

Marsh-thistle

Invasive in upper Midwest, known from New Hampshire. Eurasia; G&C-613.

Balsaminaceae

Impatiens glandulifera Royle

Invasive in parts of Maine and Maritime Provinces. Himalyan region; G&C-362.

Cyperaceae

Carex kobomugi Ohwi

Invasive on coastal dunes in New Jersey and New York, currently at on site along Rhode Island coast; eastern Asia; G&C-709.

Hydrocharitaceae

Hydrocharis morsus-ranae L.

European Frog's bit

Known to occur in Lake Champlain, Vermont. Europe; G&C-638.

Menyanthaceae

Nymphoides peltata (Gmelin) Kuntze

Yellow Floating-heart

Listed as an invasive in Massachusetts. Europe; G&C-413.

Poaceae

Glyceria maxima (Hartman) Holmburg

Tall Mannagrass

Invasive in parts of the Midwest and Canada, currently known in New England from Massachusetts. Eurasia; not in G&C; see Anderson, J.E. &A.A. Reznicek. 1994. Glyceria maxima (Poaceae) in New England. Rhodora 96:97-101.

Polygonaceae

Polygonum perfoliatum L.

Mile-a-minute Vine

Known to occur in Westchester County, New York, little more than 1 mile from the Connecticut line. First reported there in 1995 by which time it was well established. Eastern Asia; G&C-138.

Trapaceae

Trapa natans L.

Water Chestnut

Known to be invasive in eastern Massachusetts and along the Hudson River in New York. It has been reported near the Connecticut River in Massachusetts. Eurasia; G&C-313.