Fact
Sheets
Alien Plant Invaders
Yes, they are here. Plant invaders from other parts of the world
are becoming more common, wrecking havoc with our natural environment.
According to the Pacific Northwest Exotic Pest Plant Council, more
than 160 different nonnative plants are alien invaders in Oregon
and Washington. When these plants become weedy, they contribute
the decline of our quality of life through altering the ecological
balance of our native and wildland habitats.
Many come from garden plants, herbs, lawn and forage grasses, aquarium
plants, and even escaped agricultural crops. Some, like foxglove,
arrived with the first European settlers, and are now so widespread
some people consider them natives. Here we explain how you can do
your part to protect natural ecosystems against these species.
For your convenience, we have edited the list to include only those
you might see for sale as garden plants. These are listed by groups,
with trees first, followed by shrubs and garden herbaceous plants,
and so on. Those with the most potential for invading wild areas
are marked with a :( . Plant species
being considered for their invasive potential are marked with a
***.
What You Can do:
The following list includes those invaders most commonly spread
through horticultural use. Please help by:
- Not purchasing these plant species
- Eliminating them from your own gardens, and
- Spreading the word about their potential damage to wild ecosystems.
Trees
- Tree of heaven (Ailanthus altissima) :(
- English hawthorne (Crataegus monogyna)
- Russian-olive (Elaeagnus angustifolia) :(
- Mulberry (Morus alba)
- White poplar (Populus alba) :(
- Bird cherry (Prunus avium)
- Sour cherry (Prunus cerasus) ***
- Mahaleb cherry (Prunus mahaleb)
- Black locust (Robinia pseudoacacia) :(
- European mountain-ash (Sorbus aucuparia)
- Tamarisk (Tamarix pentandra) :(
- Siberian elm (Ulmus pumila)
-
- Shrubs & Vines
Butterfly bush (Buddleja davidii) :(
- Scotch broom (Cytisus scoparius):(
- Spurge laurel (Daphne laureola) :(
- French broom (Genista monspessulanus) :(
- English ivy (Hedera helix) :(
- English holly (Ilex aquifolium):(
- English laurel (Prunus laurocerasus)
- Red current (Ribes rubrum)
- Dog rose (Rosa canina)
- Sweetbriar (Rosa eglanteria)
- Elm Bramble (Rubus ulmifolius) ***
- Basket willow (Salix purpurea) ***
- Spanish broom (Spartium junceum) ***
- Puncture vine (Tribulus terrestris)
-
- Common Herbaceous Garden Plants
- Red valerian (Centranthus ruber)
- Dwarf snapdragon (Chaenorrhinum minus) ***
- Foxglove (Digitalis purpurea)
- Garden rocket (Eruca vesicaria ssp. salvia) ***
- Baby's breath (Gypsophila paniculata):(
- Burning bush (Kochia scoparia):(
- Dalmatian toadflax (Linaria gensitifolia ssp. dalmatica):(
- White campion (Lychnis alba)
- Garden loosestrife (Lysimachia vulgaris) ***
- Loosestrife (Lythrum virgatum)
- Four o’clock (Mirabilis nyctaginea) :(
- Fountain grass (Pennisetum setaceum):(
- Lesser periwinkle (Vinca minor)
- Less Common Herbaceous Garden Plants
Bidi-bidi (Acaena novae-zelandica) ***
- Indigo bush (Amorpha fruticosa):(
- Small bugloss (Anchusa arvensis) ***
- Common bugloss (Anchusa officinalis) ***
- Tall oatgrass (Arrhenantherum elatium)
- White bryony vine (Bryonia alba):(
- Knapweed (Centaurea most Centaurea are suspect)
- Orchard grass (Dactylis glomerata)
- Venice mallow (Hibiscus trionum):(
- Orange hawkweed (Hieracium aurantiacum) :(
- Yellow toadflax (Linaria vulgaris)
- Tree lupine (Lupinus arboreus):(
- Japanese knotweed (Polygonum cuspidatum):(
- Devil's claw (Proboscidea louisianica):(
- Moth mullein (Verbascum blattaria)
- Wooly mullein (Verbascum thapsus)
Plants for Wet Gardens or Water
Gardens
Yellow flag (Iris pseudacorus):(
Purple loosestrife (Lythrum salicaria):(
Watercress (Rorippa nasturium-aquaticum):(
European beachgrass (Ammophila arenaria):(
Herbs or Dye Plants
Chervil (Anthriscus sylvestris)
Absinth wormwood (Artemisia absinthium)
Fennel (Foeniculum vulgare):(
Herb Robert (Geranium robertianum) :(
Dyer’s woad (Isatis tinctoria):(
- Lawn Grasses
Tall fescue (Festuca arundinacea)
- Italian ryegrass (Lolium multiflorum)
- Perennial ryegrass (Lolium perenne)
- Kentucky bluegrass (Poa pratensis):(
-
- Aquarium, Pond, and Beach Plants
Elodea (Egeria densa)
- Hydrilla (Hydrilla verticillata):(
- Spiked water-milfoil (Myriophyllum spicatum):(
KEY: The most potential to
invade: :(
Under consideration: ***
Also, check out these web sites for additional info:
The
Bureau of Land Management (www.blm.gov/education/weeds/help.html)
King
County, Washington (http://dnr.metrokc.gov/wlr/lands/weeds/weed_info.htm)
Source: Non-Native Pest Plants
of Greatest Concern in Oregon and Washington as of August 1997. PNS
Exotic Pest Plant Council, c/p Dr. Sarah Reichard, University of Washington,
Center for Urban horticulture, Box 354115, Seattle, WA 98195. Information
used with permission.
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