| Invasive plant list continues to grow in Oregon |
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by Cynthia Orlando, Agency Affairs Specialist, certified arborist
Invasive species have contributed to the decline of more than 40 percent of the nation's threatened and endangered native species.
There are dozens of invasive species in our state and many more not yet sighted here but worth watching out for. But just what is an invasive species? The term "invasive species" refers to non-native species, including both plants and animals, whose introduction is likely to cause economic or environmental harm, or harm to human health.
Giant hogweed, cordgrass, and garlic mustard are a few examples of invasive plants worth learning about and preventing, whenever possible.
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| Giant hogweed (Heracleum mantegazzianum) |
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Giant Hogweed (also called giant cow parsley), native to Central Asia, has a stout, dark reddish-purple stem with hollow, spotted leaf stalks and sturdy bristles. This perennial has tuberous rootstalks and numerous white flowers clustered in an umbrella-shaped head that is up to 80 cm (2.5 ft) in diameter across its flat top. This plant, which can reach 2-5 meters in height, is phototoxic; that means its sap can cause severe skin inflammations when the skin is exposed to sunlight or to UV-rays.
At first, skin will turn red and start itching, then blisters form which may result in black or purplish scars that can last several yeras. Hospitalisation may be necessary. Presence of minute amounts of sap in the eyes can lead to temporary or even permanent blindness.
Hogweed is regulated as a federal noxiouos weed by the U.S. Government; because of its phototoxicity and its invasive nature, Giant Hogweed is often actively removed.
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Images courtesy of Tim Butler, Oregon Department of Agriculture
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Oregon Department of Agriculture Plant Division, Noxious Weed Control - giant hogweed web page
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| Smooth cordgrass (Spartina alterniflora) |
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Smooth cordgrass (Spartina alterniflora) is a tall clumping perennial grass with creeping rehizomes that grows up to 7 ft in height. This plant has been introduced by humans to wetlands in Oregon, Washington and California, both accidentally and intentionally. Leaves have flat blades 12 to 20 in. long, and flowering takes place June to November. Where introduced, smooth cordgrass fills in mudflat habitats, resulting in the loss of habitat for oysters and salmon.
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S. alterniflora plant
Photo by: V. Howard,
PSU-CLR
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Ligule on S. alterniflore
Photo by: C. Cornu,
South Slough NERR
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Typical S. alterniflora mats at Willapa Bay in Washington
Photo by: T. Forney, ODA
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Oregon Department of Agriculture Plant Division, Noxious Weed Control - smooth cordgrass web page
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| Garlic mustard (Alliaria petiolata) |
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You may have read about Garlic mustard (Alliaria petiolata) within the pages of this publication before; yes, garlic mustard is still a problem in Oregon. How to identify it?
This cool-season biennial's leaves and stems emit the smell of garlic or onion when crushed. Plants are 12 to 48 inches in height, and in their second year, produce numerous white flowers with four separate petals. Garlic mustard is the only plant of this height in the woods with white flowers in May. Hand-pulling before flowering is recommended.
Oregon Department of Agriculture Plant Division, Noxious Weed Control - garlic mustard web page
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