Lesser Celandine, Ficaria verna

Plants on the DISC list included species that are non-native to Delaware, have the potential for widespread dispersal and establishment, can out-compete other species in the same area, and have the potential for rapid growth, high seed or propagule productions and establishment in natural areas.  Each species was chosen by a committee of experts in environmental science and botany after an intensive environmental assessment.

The first Delaware Invasive Species Council (DISC) assessment of invasive plants was conducted in 2003, and followed protocol developed by NatureServe. A second assessment was done in 2006, following the same protocol. After the 2006 assessment, DISC developed three invasive categories – widespread and invasive, restricted and invasive, and restricted and potentially invasive. In 2019, DISC recognized that a revision of the 2006 list of invasive plants was needed, and that the NatureServe protocol should be modified to make it more relative to the state of Delaware. This current assessment is based on this modified protocol and intended for educational purposes 

The protocols are documented in the Plant Species Assessment Protocol document.

Based on the expert assessments, an I-Rank, or invasive rank was determined based on expert responses denoting the level at which a species is invasive in the identified geographic area, in this case, the state of Delaware. These ranks are categorized by high, medium, low, and insignificant. If a species was ranked as high, medium, or low, they are deemed invasive to some degree by the experts and; therefore, are included in the current iteration of the DISC list of Invasive Plant Species. Species ranked as insignificant, were added to the DISC Watch List and will be reevaluated in two years when the list will again be revised. Additionally, for future revisions to the list, selected species thought to be invasive in Delaware will also be evaluated. In contrast to the 2006 DISC list of invasive plants, the new list includes only two categories – invasive and watch list. Below are the results.

Download the DISC Invasive Plant List Conclusion Document Here

DISC Invasive Plant List

SpeciesCommon Name
Acer palmatumJapanese maple
Acer platanoidesNorway maple
Acorus calamusEuropean sweetflag
Ailanthus altissimaTree of heaven
Alliaria petiolataGarlic mustard
Ampelopsis glandulosaPorcelain berry
Berberis thunbergiiJapanese barberry
Celasrus orbiculatusOriental bittersweet
Centaurea stoebe subsp. micranthosSpotted knapweed
Clematis ternifloraJapanese Clematis
Elaeagnus umbellataAutumn olive
Eragrostis curvulaWeeping lovegrass
Euonymus alatusWinged euonymus
Euonymus fortuneiWintercreeper
Fallopia japonicaJapanese knotweed
Ficaria vernaLesser celandine
Hedera helixEnglish ivy
Hemerocallis fulvaOrange daylily
Hydrilla verticillataHydrilla
Iris pseudacorusYellow flag iris, Water flag
Koelreuteria paniculataGolden raintree
Leucojum aestivumSummer snowflake
Ligustrum vulgareEuropean privet
Lonicera japonicaJapanese honeysuckle
Lonicera maackiiAmur honeysuckle
Lonicera morrowiiMorrow’s honeysuckle
Lonicera tataricaTartarian honeysuckle
Lysimachia nummulariaCreeping jenny
Lythrum salicariaPurple loosestrife
Microstegium vimineumJapanese stilt grass
Miscanthus sinensisChinese silvergrass
Murdannia keisakMarsh dewflower
Pachysandra terminalisJapanese pachysandra
Persicaria perfoliataMile-a-minute
Phalaris arundinaceaReed canarygrass
Phragmites australis subsp. australisEuropean reed
Pinus thunbergianaJapanese black pine
Pyrus calleryanaCallery pear
Rosa multifloraMultiflora rose
Rubus phoenicolasiusWineberry
Viburnum dilatatumLinden arrowwood
Viburnum sieboldiiSiebold’s viburnum
Vinca minorLesser periwinkle
Wisteria sinensisChinese wisteria

DISC Invasive Plant Watch List

SpeciesCommon Name
Buddleja davidiiButterfly bush
Ilex crenataJapanese holly
Lespedeza thunbergiiThunberg’s bushcover
Lilium lancifoliumTiger lily
Lotus corniculatusBird’s foot trefoil
Mahonia bealeiLeatherleaf mahonia
Quercus acutissimaSawtooth oak
Spirea japonicaJapanese spirea
Viburnum plicatumJapanese snowball
Viburnum setigerumTea viburnum