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:

• WeedWise: Priority
• State of Oregon: Class A,T
• State of Washington: not listed
• Four County CWMA: not listed

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

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:

• WeedWise: Priority
• State of Oregon: Class A,T
• State of Washington: Class B
• Four County CWMA: A
• Columbia Gorge CWMA: A

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