Tag Archives | priority


November’s Weed of the Month: Spurge Laurel

The Scourge of Spurge Laurel Spurge laurel (Daphne laureola) is neither a spurge nor a laurel, but rather an invasive plant in the Daphne family.  This perennial plant has poisonous berries, spreads aggressively in our native forests, and is increasingly being found in Clackamas County. Native to Europe, spurge laurel was introduced in Oregon as […]

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Plant Identification: What is that Weed?

Do you think you’ve found a noxious weed?  Here is how you can get help to identify and report your find! One of the most important aspects in controlling invasive weeds is to verify the identification if invasive weeds before you work to control them.  Knowing the difference between an aggressive weed and a common […]

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September’s Weed of the Month: Knotweed

September is the Time to Control Japanese Knotweed Japanese knotweed (Fallopia japonica) has been called a “nightmare” and a “botanical bully,” and is one of the 100 worst global invaders. These characterizations give you a pretty good idea of just how unwelcome this invasive weed is in our community. Japanese knotweed is fast growing and […]

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August’s Weed of the Month: Puncturevine

Puncturevine (Tribulus terrestris) is aptly named! This invasive weed has spiny seed heads that can easily puncture a bike tire, inflatable raft, animal paw, or footwear. Be on the lookout because it is beginning to make its way into Clackamas County from eastern and southern Oregon. Also known as “goathead”, puncturevine is native to southern […]

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June’s Weed of the Month: Policeman’s Helmet

Policeman’s helmet (Impatiens glandulifera) is an invasive weed which grows in ditches, wetlands, and along waterways. Native to India, this fast-growing annual was introduced as a ornamental plant due to its impressive growth and the showy purple, pink or white blooms. Since introduction, it has escaped cultivation to become the dominate riparian vegetation in many […]

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Orange hawkweed in bloom

May’s Weed of the Month: Orange Hawkweed

Orange hawkweed (Hieracium aurantiacum) is a relatively new invasive weed in Clackamas County.  With your help, our team plans to keep it from becoming a common problem for landowners! A member of the sunflower family, orange hawkweed is native to central and southern Europe and grows in open areas like gravel pits, roadsides, meadows, pastures, […]

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April’s Weed of the Month: Garlic Mustard

Garlic mustard (Alliaria petiolata) is an increasingly invasive weed in our community.  Native to central and western Europe, this fast-growing plant commonly invades sites such as parks, trails, roadsides, and streamsides. April is a great time to manage this priority invasive weed on your property. Sometimes referred to as Jack-by-the-hedge, garlic mustard is easily identified […]

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Garden loosestrife (Lysimachia vulgaris)


Common names:

Garden loosestrife, garden yellow loosestrife,

Scientific Name:

Lysimachia vulgaris


Garden loosestrife is a tall upright rhizomatous noxious weed that grows up to 5 feet in height.  It is characterized by terminal panicles of bright yellow 5-petaled flowers.  Leaves are opposite to whorled, nearly sessile and lanceolate 7-12 cm in length.  The stems and leaves are soft and hairy.  Flowered are ringed by distinctive orange-margined green sepals. Underground rhizomes can spread to lengths up to 15 feet.  Plants reproduce from both rhizomes and seeds.

Life cycle:


Height of mature plants

3 to 6 feet

Flower color:

Yellow 5- petaled flower, that lack reddish or black streaks or dots

Bloom time:

Typically blooms during July and August.


The closely related Yellow loosestrife (Lysimachia punctata) is a less aggressive garden ornamental, with lower flowers from emerging from the leaf axils, and the yellow flowers lack the orange-margined sepals, characteristic of the noxious garden loosestrife.


Garden loosestrife is found escaping in wetlands and along streams and river.  It is also likely to be found in garden setting.  This species is known to occur in only one location in Oregon.


Garden loosestrife invades wetland and riparian areas, where it displaces desirable native vegetation.  Once established it can spread rapidly, and has been known to displace very hearty plants such as cattails.  Invasion by garden loosestrife disrupts habitat for fish and wildlife, and can limit recreation opportunities in highly invaded sites.

Noxious Weed Listing:


This species is native to Europe.

Present in Clackamas County:



Oregon Noxious Weed Profile

USDA Plants

King County Noxious Weed Program

Invasive Plant Atlas of New England


WeedWise Program