WA Invasive Ranking System
Phragmites australis ssp. australis along Lower Crab Creek
The presence and abundance of invasive plants are frequently used in function and condition assessment tools. Existing state lists of noxious weeds and invasive species serve valuable purposes, but incorporate economic impacts and other values that don’t always identify the plant species that are most impactful to the ecology of natural ecosystems. With the assistance of regional experts, Washington Natural Heritage Program staff are working to assemble a consistent, defensible list of the most ecologically impactful invasive plant species in Washington State.
The Washington Invasive Ranking System (WIRS) is a method for assessing the ecological impact of nonnative plant species in natural ecosystems of Washington State. The primary output of WIRS is an Ecological Impact rank, which indicates the degree of ecological degradation caused by a given plant in the ecosystems in which it is found. WIRS also produces supplementary information related to each plant’s management difficulty, biological characteristics, and distribution and abundance.
For complete results for all plants assessed to date, see:
- WIRS Database (Excel)
To access individual species assessments, click on the hyperlinked scientific names in the table below.
| Scientific Name | Common Name | Ecological Impact Rank |
|---|---|---|
| Acer negundo | Box elder | Low |
| Ailanthus altissima | tree of Heaven | Moderate |
| Alliaria petiolata | garlic mustard | High |
| Alopecurus pratensis | field meadow-foxtail | Moderate |
| Amorpha fruticosa | Indigobush | Moderate |
| Anthoxanthum odoratum | sweet vernalgrass | Moderate |
| Arrhenatherum elatius | tall oatgrass | Moderate |
| Arum italicum ssp. italicum | Italian arum | Low |
| Arundo donax | giant reed | High |
| Bellardia viscosa | Yellow glandweed | Low |
| Bellis perennis | English daisy | Insignificant |
| Betula pendula | European white birch | Low |
| Butomus umbellatus | flowering rush | High |
| Centaurea solstitialis | yellow star-thistle | High |
| Chondrilla juncea | rush skeletonweed | High |
| Cirsium arvense | Canada thistle | High |
| Cirsium vulgare | bull thistle | Low |
| Clematis vitalba | old man’s beard | Moderate |
| Cotoneaster spp. | cotoneaster | Low |
| Crataegus monogyna | English hawthorn | High |
| Cynoglossum officinale | houndstongue | Moderate |
| Dianthus armeria | Deptford pink | Insignificant |
| Dipsacus fullonum | common teasel | Moderate |
| Erechtites minimus | toothed coast fireweed | Low |
| Fallopia × bohemica | Bohemian knotweed | High |
| Hieracium pilosella | mouse-ear hawkweed | Low |
| Holcus lanatus | common velvetgrass | Moderate |
| Ilex aquifolium | English holly | High |
| Impatiens capensis | spotted jewelweed | Low |
| Iris pseudacorus | yellow flag iris | High |
| Jacobaea vulgaris | stinking willie | Moderate |
| Juglans regia | English walnut | Low |
| Juncus effusus subsp. effusus | common rush | Low |
| Lamium galeobdolon | yellow archangel | Low |
| Lathyrus latifolius | everlasting-pea | Low |
| Lathyrus sylvestris | narrow-leaf pea | Low |
| Leucanthemum vulgare | oxeye daisy | Moderate |
| Lysimachia nummularia | garden loosestrife | Low |
| Lythrum salicaria | purple loosestrife | Moderate |
| Marrubium vulgare | white horehound | Insignificant |
| Mycelis muralis | wall lettuce | Insignificant |
| Myosotis discolor | yellow and blue scorpiongrass | Insignificant |
| Myriophyllum heterophyllum | variable-leaf milfoil | High |
| Myriophyllum spicatum | Eurasian watermilfoil | High |
| Nasturtium officinale | watercress | Moderate |
| Phalaris arundinacea | reed canarygrass | High |
| Phleum pratense | Timothy | Low |
| Plantago lanceolata | English plantain | Insignificant |
| Poa annua | annual bluegrass | Insignificant |
| Potamogeton crispus | curlyleaf pondweed | High |
| Quercus robur | English oak | Low |
| Rosa canina | dog rose | Moderate |
| Rosa multiflora | multiflora rose | Moderate |
| Rosa rugosa | rugosa rose | Low |
| Rubus bifrons | Himalayan blackberry | High |
| Rubus laciniatus | cut-leaf blackberry | Moderate |
| Rumex crispus | curly dock | Insignificant |
| Sasa palmata | broadleaf bamboo | Moderate |
| Schedonorus arundinaceus | tall fescue | Moderate |
| Schoenoplectus mucronatus | ricefield bullrush | Low |
| Senecio sylvaticus | woodland groundsel | Insignificant |
| Solanum dulcamara | bittersweet nightshade | Low |
| Solidago altissima | late goldenrod | Moderate |
| Spartina alterniflora | smooth cordgrass | High |
| Tamarix ramosissima | saltcedar | High |
| Trifolium pratense | red clover | Low |
| Trifolium subterraneum | burrowing clover | Low |
| Utricularia inflata | wwollen bladderwort | High |
| Verbascum blattaria | moth mullein | Insignificant |
| Veronica anagallis-aquatica | water speedwell | Insignificant |
| Veronica arvensis | wall speedwell | Insignificant |
