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.

DISC Invasive Plant List

SpeciesCommon Name
Acer palmatumJapanese maple
Acer platanoides Norway maple
Acorus calamus European sweetflag
Ailanthus altissima Tree of heaven
Alliaria petiolata Garlic mustard
Ampelopsis glandulosa Porcelain berry
Berberis thunbergii Japanese barberry
Celasrus orbiculatus Oriental bittersweet
Centaurea stoebe subsp. micranthos Spotted knapweed
Clematis terniflora Japanese Clematis
Elaeagnus umbellata Autumn olive
Eragrostis curvula Weeping lovegrass
Euonymus alatus Winged euonymus
Euonymus fortunei Wintercreeper
Fallopia japonica Japanese knotweed
Ficaria verna Lesser celandine
Hedera helix English ivy
Hemerocallis fulva Orange daylily
Hydrilla verticillata Hydrilla
Iris pseudacorus Yellow flag iris, Water flag
Koelreuteria paniculata Golden raintree
Leucojum aestivum Summer snowflake
Ligustrum vulgare European privet
Lonicera japonica Japanese honeysuckle
Lonicera maackii Amur honeysuckle
Lonicera morrowii Morrow’s honeysuckle
Lonicera tatarica Tartarian honeysuckle
Lysimachia nummularia Creeping Jenny
Lythrum salicaria Purple loosestrife
Microstegium vimineum Japanese stilt grass
Miscanthus sinensis Chinese silvergrass
Murdannia keisak Marsh Dewflower
Pachysandra terminalis Japanese pachysandra
Persicaria perfoliata Mile-a-minute
Phalaris arundinacea Reed canarygrass
Phragmites australis subsp. australis European reed
Pinus thunbergiana Japanese black pine
Pyrus calleryana Callery pear
Rosa multiflora Multiflora rose
Rubus phoenicolasius Wineberry
Viburnum dilatatum Linden arrowwood
Viburnum sieboldii Siebold’s viburnum
Vinca minor Lesser periwinkle
Wisteria sinensis Chinese wisteria

DISC Invasive Plant Watch List

SpeciesCommon Name
Buddleja davidii Butterflybush
Ilex crenata Japanese holly
Lespedeza thunbergii Thunberg’s bushcover
Lilium lancifolium Tiger lily
Lotus corniculatus Bird’s foot trefoil
Mahonia bealei Leatherleaf mahonia
Quercus acutissima Sawtooth oak
Spirea japonica Japanese spirea
Viburnum plicatum Japanese snowball
Viburnum setigerum Tea viburnum

Download the DISC Invasive Plant List Conclusion Document Here