Tag Archives | Class A

Goatsrue Eradication Project

Since 2016, the WeedWise program has been working to control the largest known infestation of goatsrue (Galega officinalis) in Oregon. Goatsrue is an Oregon class A noxious weed and has been deemed a high priority for control and eradication because it is toxic to livestock and spreads easily.  This federal and state noxious weed is only known at a handful of other sites across Oregon and the Pacific Northwest.

Goatsrue flowers

About Goatsrue

Goatsrue is a deep-rooted perennial, with hollow stems and compound alternate leaves.  The compound leaves have a terminal leaflet and 6-10 pairs of leaflets. The tip of each leaflet rapidly narrows to a fine tip. Goatsrue has pea-like flowers that vary in color from purple to white. Flowers bloom from June to October and are clustered at the end of its branches or at the leaf axils. Unlike some other members of the pea family, goatsrue lacks tendrils and grows in a more upright and bushy form rather than as a vine. The seeds are contained in pods with up to 9 mustard-colored, oblong seeds. Each plant can produce 15,000 pods a year. Additionally, these seeds may remain viable for 5-10 years in the soil.

Goatsrue closely resembles some regionally rare native plants, so we encourage landowners to contact us if they think they may have goatsrue on their property.

Robust goatsrue growth

What we Found

In May of 2016, during one of our planned weed surveys, one of our contracted survey crews discovered a large previously unknown population of goatsrue on two adjacent riparian properties along the Clackamas River. This infestation affects 14 acres and is the largest known infestation of goatsrue in Oregon. At that time, we began a management effort to contain and control this priority weed with the goal of eradication of the goatsrue as well as several other priority invasive plants present at these sites.

This discovery was found as part of extensive surveys of streamside properties along the Clackamas River initiated in 2015 and continuing into the present. Twenty-one priority invasive plant species were on our target list for these surveys. Some of these species had been documented in our region and some had not. These surveys help us to address new priority invasive plants and better manage priority invasive plants established here. We thank private landowners for allowing us to access their properties for these surveys!

Goatsrue herbicide application

What we are doing

The WeedWise Program initiated control soon after detection of this large infestation. Our approach began confirming the identity of the goatsrue. We then followed up with a thorough review of the biology and control of goatsrue. Most notably, we learned that goatsrue can have a long seed dormancy period allowing seeds to grow after 10 years in the soil. As a perennial weed with a deep taproot, it is all difficult to remove by hand. Therefore, our management goals were to prevent all seed production and to target the large root systems of existing plants.

Next, we researched management strategies appropriate for this plant and this site. We also consulted with the Oregon Department of Agriculture Noxious Weed Control Program and the City of Portland Bureau of Environmental Services who both have prior experience managing goatsrue. Based on this research, we selected two herbicides to treat the infestation: one to target upland populations and a second aquatically approved herbicide to treat infestations that occur near water. The herbicide applications were planned by the WeedWise program and implemented using licensed restoration contractors.

What’s Next?

To date, our management efforts have been highly successful, but with the size and complexity of the site we did note some patches with regrowth after herbicide application, as well as new seedlings emerging. On follow-up monitoring of the site, we also found several overlooked patches that had grown in an among other vegetation. In response, our current efforts focus on continuing to scout for missed populations and to remove interspersed invasive Himalayan blackberry (Rubus bifrons) stands which may obscure goatsrue plants. We are carrying out multiple rounds of control each year to ensure that we are not letting any plants go to seed and to continue to address regrowth.

After two years of intensive control, we have dramatically reduced the populations and are on track to eradicate this population. Eradication will require ongoing monitoring and control to address the long seed dormancy. Although we won’t be walking away from the site anytime soon, we are optimistic knowing that the population is significantly reduced, and that we are committed to eradicating goatsrue from Clackamas County!

Project Photo Gallery

Welted thistle (Carduus crispus)

Gallery:

Common names:

Welted thistle, curly plumeless thistle

Scientific Name:

Carduus crispus

Description:

A large growing thistle Stems are openly branching, hairy with curled hairs to nearly smooth. Stems have spiny wings to 1.5 cm wide, and sport wing spines 3 mm long. The leaves have winged petioles at their base. Leaf blades are 10–20 cm long with spiny-toothed margins. Flower heads are borne singly or in groups of 2–5, 15–18 mm wide. Flower peduncles are spiny-winged to near apex or throughout, to 4 cm wide. Flower corollas can be either purple or white. Flower parts are both male and female.  Insect pollination is required. Reproduction is entirely by seed.  Carduus crispus closely resembles the more common C. acanthoides (plumeless thistle).

Life cycle:

Annual to biennual

Height of mature plants

1- 5 feet

Flower color:

Purple or pink to white

Bloom time:

Flowering occurs July through September.

Look-a-likes:

Similar to other thistles.  Very closely resembles the more common plumeless thistle (Carduus acanthoides)

Habitat:

irrigation ditches, field margins, waste ground, pastures, and roadsides

Impacts:

Likely contaminant in grass and alfalfa hay, reducing its quality and marketability. Welted thistle seeds may also be a contaminant in alfalfa, grain, or grass seed. Infested grasslands and pastures may see a reduction in productivity when thistle densities reach high levels. This spiny thistle would act as a deterrent to most grazing.

Noxious Weed Listing:

Origin:

Native to Europe and Asia.  The first record of welted thistle occurred in the Eastern U.S. in 1974. In 2016, a new western infestation was detected in Wallowa County, Oregon.

Present in Clackamas County:

Not known to occur

Links:

Oregon Noxious Weed Risk Assessment

Plants Database Profile: Carduus crispus

CABI Invasive Species Compendium Datasheet

 

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The new thistle you don’t want on your property!

We have plenty of thistles growing in our area and landowners across the region are working hard to combat these prickly invaders.  While most of the thistles growing in our area are invasive, some of them are actually native.  Unfortunately, a recent discovery from eastern Oregon marks the addition of a new invasive thistle to […]

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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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Garden loosestrife (Lysimachia vulgaris)

Gallery:

Common names:

Garden loosestrife, garden yellow loosestrife,

Scientific Name:

Lysimachia vulgaris

Description:

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:

Perennial

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.

Look-a-likes:

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.

Habitat:

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.

Impacts:

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:

Origin:

This species is native to Europe.

Present in Clackamas County:

No

Links:

Oregon Noxious Weed Profile

USDA Plants

King County Noxious Weed Program

Invasive Plant Atlas of New England

 

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Purge the surge in spurge!

This past season we have seen a rise in the number of Oblong spurge (Euphorbia oblongata) sites appearing in Clackamas County.  Oblong spurge is a class A noxious weed in the state of Oregon, and eradication of this species is required across the state.  It is known to be highly aggressive and can displace native […]

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