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Invasive Exotic Plants of the Northeast

The inclusion of some by now well known plants may surprise you, however in some cases it is the plant's distinguishing characteristic which has resulted in its introduction and widespread use in cultivation. Most plants listed have by now far outreached cultivation and have escaped into our local communities. The goal is to curtail their use in landscaping, develop methods to contain them and find non-invasive substitutes when possible. The Connecticut College Arboretum's policy on this point is to remove woody invasive exotics within the Plant Collections.

Please View the list by these catagories: Trees, Shrubs, WoodyVines, HerbaceousVines, Herbaceous Plants, Aquatics

For detailed information on invasive exotic plant species in Connecticut, visit the Connecticut Invasive Plant Working Group.

This is a draft list of non-native invasive vascular plants known to occur in Connecticut that will be included in a forthcoming book to be published by the State Geological and Natural History Survey of Connecticut. This list has no legal status. The 3 ranks, Widespread and Invasive, Restricted and Invasive and Potentially Invasive. The criteria for assigning ranks are from the forthcoming book These are currently being reviewed. An appendix of species about which I have questions is included. The questions range from whether or not people have seen this species naturalized in Connecticut, is it really invasive away from managed areas, or it has been suggested by someone knowledgeable about the state's flora but the records are not their to support the inclusion at this time. If you can help, please send me information of these taxa including your name, best way and time to reach you and localities where you have seen this species invade.

Names follow Gleason & Cronquist's Manual of Vascular Flora, 2nd Edition 1991 or Flora of North America, Volumes 2 and 3, 1993+. Again, if you have questions, please contact the author. Any comments or thoughts would be appreciated.

Acer ginnala L. Amur Maple

[Potentially Invasive]

Acer platanoides L. Norway Maple

[Potentially Invasive]

Acer pseudoplatanus L. Sycamore Maple

[Potentially Invasive]

Ailanthus altissima (Mill.) Swingle Tree-of-heaven

[Widespread and Invasive]

Paulownia tomentosa (Thunb.) Steudel Empress-tree

[Potentially Invasive]

Populus alba L. White Poplar

[Potentially Invasive]

Robinia pseudoacacia L. Black Locust

[Widespread and Invasive]

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Amorpha fruticosa L. False Indigo

[Potentially Invasive]

Berberis thunbergii DC. Japanese Barberry

[Widespread and Invasive]

Berberis vulgaris L. Barberry

[Potentially Invasive]

Elaeagnus angustifolia L. Russian Olive

[Potentially Invasive]

Elaeagnus umbellata Thunb. Autumn Olive

[Widespread and Invasive]

Euonymus alatus (Thunb.) Sieb. Winged Euonymus

[Widespread and Invasive]

Frangula alnus Mill. European Buckthorn

[Widespread and Invasive]

Ligustrum obtusifolium Sieb. & Zucc. Border Privet

[Potentially Invasive]

Ligustrum ovalifolium Hassk. California Privet

[Potentially Invasive]

Ligustrum vulgare L. European Privet

[Potentially Invasive]

Lonicera ´ bella Zabel Bella Honeysuckle

[Widespread and Invasive]

Lonicera maackii (Rupr.) Maxim. Amur Honeysuckle

[Potentially Invasive]

Lonicera morrowii A. Gray Morrow's Honeysuckle

[Widespread and Invasive]

Lonicera tatarica L. Tatarian Honeysuckle

[Potentially Invasive]

Lonicera xylosteum L. European Fly-honeysuckle

[Potentially Invasive]

Rhamnus cathartica L. Buckthorn

[Widespread and Invasive]

Rosa multiflora Thunb. Multiflora Rose

[Widespread and Invasive]

Rubus phoenicolasias Maxim. Wineberry

[Restrcited and Invasive]

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Ampelopsis brevipedunculata (Maxim.) Trautv. Porcelain berry

[Restrcited and Invasive]

Celastrus orbiculatus Thunb. Asiatic Bittersweet

[Widespread and Invasive]

Lonicera japonica Thunb. Japanese Honeysuckle

[Widespread and Invasive]

Pueraria lobata (Willd.) Owhi Kudzu-vine

[Potentially Invasive] syn. Pueraria montana var. lobata

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Humulus japonicus Sieb. & Zucc. Japanese Hops

[Potentially Invasive]

Polygonum perfoliatum L. Mile-a-minute Vine

[Potentially Invasive]

Solanum dulcamara L. Climbing Nightshade

[Potentially Invasive]

Vincetoxicum nigrum (L.) Moench. Black Swallow-wort

[Widespread and Invasive]

Vincetoxicum rossicum (Kleo.) Barb. Swallow-wort

[Widespread and Invasive]

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Aegopodium podagraria L. Goutweed

[Potentially Invasive]

Aira caryophyllea L. Silver Hairgrass

[Potentially Invasive]

Alliaria petiolata (Bieb.) Cavara & Grande Garlic Mustard

[Widespread and Invasive]

Allium vineale L. Wild Garlic

[Potentially Invasive]

Arthraxon hispidus (Thunb.) Makino

[Potentially Invasive]

Bromus inermis Smooth Brome

[Potentially Invasive]

Bromus tectorum L. Drooping Brome-grass

[Potentially Invasive]

Cardamine impatiens L.

[Restrcited and Invasive]

Centaurea maculosa L. Spotted Knapweed

[Widespread and Invasive] syn. Centaurea biebersteinii

Cycloloma atriplicifolium (Spreng.) Coult. Winged Pigweed

[Potentially Invasive]

Datura stramonium L. Jimsom-weed

[Potentially Invasive]

Elsholtzia ciliata (Thunb.) Hylander Elsholtzia

[Potentially Invasive]

Euphorbia cyparissias L. Cypress Spurge

[Widespread and Invasive]

Euphorbia esula L. Leafy Spurge

[Potentially Invasive]

Froelichia gracilis (Hook.) Moq. Cottonweed

[Restrcited and Invasive]

Glechoma hederacea L. Gill-over-the-ground

[Potentially Invasive]

Geranium nepalense Sweet Nepalese Crane's-bill

[Potentially Invasive]

Hesperis matronalis L. Dame's Rocket

[Widespread and Invasive]

Iris pseudacorus L. Yellow Iris

[Restrcited and Invasive]

Kochia scoparia (L.) Schrader Summer Cypress

[Potentially Invasive]

Lepidium latifolium L. Tall Pepperwort

[Restrcited and Invasive]

Lychnis flos-cuculi L. Ragged Robin

[Potentially Invasive]

Lysimachia nummularia L. Moneywort

[Potentially Invasive]

Lysimachia vulgaris L. Garden Loosestrife

[Restrcited and Invasive]

Lythrum salicaria L. Purple Loosestrife

[Widespread and Invasive]

Microstegium vimineum (Trin.) A. Camus Japanese Stilt Grass

[Restrcited and Invasive]

Myosotis scorpioides L. Forget-me-not

[Potentially Invasive]

Ornithogalum umbellatum L. Star of Bethlehem

[Potentially Invasive]

Phalaris arundinacea L. Reed Canary-grass

[Potentially Invasive]

Phragmites australis (Cav.) Trin. Common Reed

[Widespread and Invasive]

Poa compressa L. Canada Blue-grass

[Potentially Invasive]

Polygonum cespitosum Blume

[Potentially Invasive]

Polygonum cuspidatum Sieb. & Zucc. Japanese Knotweed

[Widespread and Invasive]

Ranunculus ficaria L. Lesser Celandine

[Potentially Invasive]

Rumex acetosella L. Sheep Sorrel

[Potentially Invasive]

Tussalago farfara L. Coltsfoot

[Restricted and Invasive]

Valeriana officinalis L. Garden-heliotrope

[Potentially Invasive]

Veronica beccabunga L. Brooklime

[Potentially Invasive]

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Butomus umbellatus L. Flowering-rush

[Potentially Invasive]

Cabomba caroliniana A. Gray Fanwort

[Restrcited and Invasive]

Callitriche stagnalis Scop.

[Potentially Invasive]

Egeria densa Planchon Brazilian Water-weed

[Restrcited and Invasive]

Hydrilla verticillata (L. f.) Royle Hydrilla

[Restrcited and Invasive]

Marsilea quadrifolia L. Water Shamrock

[Potentially Invasive]

Myriophyllum aquaticum (Vell.) Verdc. Parrotfeather

[Potentially Invasive]

Myriophyllum heterophyllum Michx. Variable Water-milfoil

[Restrcited and Invasive]

Myriophyllum spicatum L. European Water-milfoil

[Widespread and Invasive]

Najas minor Allioni Eutrophic Water-nymph

[Potentially Invasive]

Nasturtium officinale R. Br. Watercress

[Widespread and Invasive]

Potamogeton crispus L. Crispy-leaved Pondweed

[Widespread and Invasive]

Trapa natans L. Water Chestnut

[Potentially Invasive]