Invasive Plants of Washington

This is a list of the non-native invasive plants that are present in Washington. It was derived from Non-native Invasive and Potentially Invasive Vascular Plants in Connecticut by Mehrhoff, L.J., K.J. Metzler and E.E. Corrigan (available as a PDF download from the Connecticut Invasive Plant Working Group website).

What makes a plant invasive? Refer to criteria here.

Please note that the terms Widespread and Invasive, Restricted and Invasive, and Potentially Invasive refer to plant status in Connecticut; status of certain plants in Washington, if different, is noted. For definitions of terms, please refer to the above website.

Widespread and Invasive

Scientific Name	Common Name	Lifeform	Habitat
Ailanthus altissima	Tree-of-heaven	T	U
Alliaria petiolata	Garlic Mustard	H	U
Berberis thunbergii	Japanese Barberry	S	U
Cardamine impatiens	No common name	H	U
Celastrus orbiculatus	Asiatic Bittersweet	V	U
Centaurea maculosa (also called Centaurea biebersteinii)	Spotted Knapweed	H	O
Cynancum louiseae	Black Swallowort	H,V	U
Elaeagnus umbellata	Autumn Olive	S	O
Euonymus alatus	Burning Bush	S	U
Fallopia japonica (also called Polygonum cuspidatum)	Japanese Knotweed	H	U,W
Frangula alnus (also called Rhamnus frangula)	European Buckthorn	S	U
Hesperis matronalis	Dame's Rocket	H	U
Iris pseudacorus	Yellow Iris	H	U
Lonicera x bella	Bella Honeysuckle	S	U,W
Lonicera japonica	Japanese Honeysuckle	V	U,W
Lonicera morrowii	Morrow's Honeysuckle	S	U,W
Lythrum salicaria	Purple Loosestrife	H	W
Microstegium vimineum	Japanese Stiltgrass	G	U
Myosotis scorpiodes	Forget-me-not	H	W
Nasturtium officinale (1)	Watercress	H	W
Phragmites australis	Common Reed	G	U,W
Rhamnus cathartica	Buckthorn	S	U
Robinia pseudoacacia	Black Locust	T	U
Rosa multiflora	Multiflora Rose	S	U

Restricted and Invasive

Scientific Name	Common Name	Lifeform	Habitat
Lonicera maakii (2)	Amur Honeysuckle	S	U
Tussilago farfara	Coltsfoot	H	U,W

Potentially Invasive

Scientific Name	Common Name	Lifeform	Habitat
Acer ginnala	Amur Maple	T	U
Acer pseudoplatanus	Sycamore Maple	T	U
Aegopodium podagraria	Goutweed	H	W
Datura stramonium	Jimson-weed	H	C
Elaeagnus angustifolia	Russian Olive	S	U
Elsholtzia ciliata	Elsholtzia	H	U
Fallopia sachalinensis (3)	Giant Knotweed	H	U
Glechoma hederacea	Gill-over-the-ground	H	W
Ligustrum (4)	Privet	S	U
Lychnis flos-cuculi	Ragged Robin	H	O
Lysimachia nummularia	Money	H	W
Phalaris arudinacea	Reed Canary Grass	G	W
Poa compressa	Canada Bluegrass	G	W
Polygonum caespitosum	No common name	H	U
Rumex acetosella	Sheep Sorrel	H	U
Solanum dulcamara	Climbing Nightshade	H,V	U,W

Key

Lifeforms:

T = tree
H = herbaceous plant
S = shrub
G = grass
V = vine
A = aquatic

Habitats:

U = uplands (all upland habitats including closed-canopy forests, second-growth woods, fields, grasslands, ridge tops, sand barrens, pitch pine scrub lands, etc.)
O = open areas (fields, grasslands, sand barrens, dry meadows, etc.)
W = wetlands (swamps, marshes, wet meadows fens, bogs, flood plains, flood plain forests, pond and stream shores)
L = lakes (ponds, impounded water)
R = rivers (streams, in running water)
C = coast (sand dunes, rocky headlands, upper edges of salt water tidal marshes)

1,3 Restricted and Invasive in Washington
2 Widespread and Invasive in Washington
4 Species present in Washington not yet determined

Please note that Giant Hogweed (Heracleum mantegazzianum) is not included in the above list as it has not yet been observed growing outside of cultivation in Washington (refer to criteria here).

Compiled and edited by E. Corrigan,
Conservation Commission
Co-chair Connecticut Invasive Plant Working Group
December, 2004

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Invasive Plants of Washington

Widespread and Invasive

Restricted and Invasive

Potentially Invasive

Key