Invasive Plant Species in Delaware

William A. McAvoy, Botanist, Delaware Natural Heritage Program

June 2001

This list contains 64 species and varieties of alien vascular plants considered to be invasive in the state of Delaware. These species are, or have extreme potential to be detrimental to natural systems, i.e., displace native vegetation and disrupt ecological processes. This list is based on personal knowledge, consultation with knowledgeable individuals, and the literature.

Species highlighted in bold are considered to be the most damaging to natural areas in the state. These species are usually shade tolerant, many have a perennial habit, many reproduce and spread primarily by seed and/or spread rapidly through vegetative means, many occur in a variety of habitat types, and many are currently widespread and abundant in the state or have high potential to become widespread.

The purpose of this list is not regulatory, it is to serve only as a reference, advising those who have an interest in alien plant species in Delaware.

SCIENTIFIC NAME

COMMON NAME

HABIT

HABITAT

Acer platanoides

Norway maple

deciduous tree

Upland forests and slopes

Acer pseudoplatanus

sycamore maple

deciduous tree

Escape from cultivation

Ailanthus altissima

tree-of-Heaven

deciduous tree

Disturbed woods, roadsides, fields

Akebia quinata

five-leaf akebia

woody vine

Cultivated and occasionally escaping

Alliaria petiolata

garlic mustard

biennial herb

Moist woods and floodplains

Ampelopsis brevipedunculata

porcelain-berry

woody vine

Moist woods, slopes and thickets

Arthraxon hispidus

joint-head arthraxon

annual grass

Disturbed areas, edges, old fields, roadsides, ditches

Berberis thunbergii

Japanese barberry

deciduous shrub

Escape from cultivation, woods and thickets

Bidens polylepis

tickseed sunflower

annual herb

Marshes, wet meadows, depressions, ditches

Cabomba caroliniana

Carolina fanwort

aquatic herb

Ponds and quiet waters

Carex kobomugi

sedge

perennial sedge

Planted on coastal dunes

Celastrus orbiculata

Oriental bitter-sweet

woody vine

Woods, floodplains, thickets

Cirsium arvense

Canada thistle

perennial herb

Meadows and old fields

Clematis terniflora

Japanese virgin's-bower

herbaceous vine

Stream and river banks, thickets, moist woods

Commelina communis

Asiatic dayflower

annual herb

Disturbed areas, edges, old fields, roadsides, ditches

Conium maculatum

poison-hemlock

biennial herb

Disturbed areas, edges, old fields, roadsides, ditches

Convolvulus arvensis

field bindweed

herbaceous vine

Meadows and old fields

Duchesnea indica

Indian mock-strawberry

perennial herb

Disturbed areas, edges, old fields, roadsides, lawns

Egeria densa

Brazilian water-weed

aquatic herb

Ponds and quiet waters

Eichhornia crassipes

water hyacinth

aquatic herb

Rare in ponds and quiet waters

Elaeagnus umbellata

autumn olive

deciduous shrub

Woods and thickets

Euonymus alata

winged euonymus

deciduous shrub

Moist woods and slopes

Festuca pratensis

meadow fescue

perennial grass

Disturbed areas, edges, old fields, roadsides, ditches

Galanthus nivalis

snow-drops

perennial herb

Escape from cultivation

Hedera helix

English ivy

woody vine

Thin woods, edges and thickets

Hemerocallis fulva

orange daylily

perennial herb

Floodplains and moist woods

Humulus japonicus

Japanese hop

perennial herb

Disturbed areas, edges, old fields, roadsides, ditches

Humulus lupulus

common hop

perennial herb

Disturbed areas, edges, old fields, roadsides, ditches

Hydrilla verticillata

hydrilla

aquatic herb

Ponds and quiet waters

Iris pseudacorus

yellow iris

perennial herb

Fresh water tidal marshes

Leucojum aestivum

summer snowflake

perennial herb

Escape from cultivation

Ligustrum vulgare

European privet

deciduous shrub

Woods and thickets

Lonicera japonica

Japanese honeysuckle

woody vine

Woodlands throughout the state

Lonicera maackii

amur honeysuckle

deciduous shrub

Woods, thickets, old fields, edges

Lonicera morrowii

Morrow’s honeysuckle

deciduous shrub

Woods, thickets, old fields, edges

Lonicera tatarica

Tartarian honeysuckle

deciduous shrub

Woods, thickets, old fields, edges

Ludwigia peploides ssp. glabrescens

floating seedbox

perennial herb

Ponds, slow shallow streams, impoundments, ditches

Lysimachia nummularia

creeping Jennie

perennial herb

Disturbed areas, edges, old fields, roadsides, ditches

Lythrum salicaria

purple loosestrife

perennial herb

Tidal and nontidal marshes, stream banks, wet meadows

Microstegium vimineum

Japanese stilt grass

annual grass

Moist woods and floodplains

Murdannia keisak

marsh dewflower

perennial herb

Marshes, ponds, ditches

Myriophyllum aquaticum

parrot feather

aquatic herb

Ponds and quiet waters

Myriophyllum spicatum

Eurasian water-milfoil

aquatic herb

Ponds and quiet waters

Pachysandra terminalis

pachysandra

perennial herb

Garden escape to woodlands

Phalaris arundinacea

reed canary grass

perennial grass

Fresh and brackish, tidal and nontidal marshes and streams

Phragmites australis

common reed

perennial grass

Widely established in wetlands

Pinus thunbergiana

Japanese black pine

evergreen tree

Coastal dunes

Pistia stratiotes

water lettuce

perennial herb

Rare in ponds and quiet waters

Poa trivialis

rough bluegrass

perennial grass

Disturbed areas, edges, old fields, roadsides, ditches

Polygonum caespitosum

tufted knotweed

annual herb

Disturbed areas, edges, old fields, roadsides, ditches

Polygonum cuspidatum

Japanese knotweed

perennial herb

Roadsides, thickets, thin moist woods, edges

Polygonum perfoliatum

mile-a-minute

annual herb

Thin moist woods, floodplains, swales and marshes

Pseudosasa japonica

bamboo

perennial grass

Edge of woods and roadsides

Pueraria montana

kudzu

herbaceous vine

Roadsides, edges of woods

Ranunculus ficaria

lesser celandine

perennial herb

Floodplains and moist woods

Rhodotypos scandens

jetbead

deciduous shrub

Cultivated and occasionally escaping

Rosa multiflora

multiflora rose

deciduous shrub

Meadows, old fields, thickets, edges

Rubus idaeus ssp. strigosus

red raspberry

deciduous shrub

Old fields, thickets, edges, hedgerows

Rubus phoenicolasius

wineberry

deciduous shrub

Disturbed areas, edges, old fields, roadsides, ditches

Sorghum halepense

Johnson grass

perennial grass

Crop land, meadows, moist swales

Trapa natans

water chestnut

aquatic herb

Rare in ponds and quiet waters

Urtica dioica

stinging nettle

perennial herb

Disturbed areas, edges, old fields, roadsides, ditches

Vinca minor

periwinkle

perennial herb

Thin woods, edges and thickets

Wisteria floribunda

Japanese wisteria

woody vine

Roadside thickets and abandoned gardens, old homesites