Weed of the Month

Learn about noxious weeds and steps you can take to manage or eradicate.  Each month we will bring you a new profile and helpful resources.

June Weed Profile

Plumeless Thistle

Carduus Acanthoides

Plumeless thistle (Carduus acanthoides) is a List B member of the Sunflower family (Asteraceae). It is a biennial or sometimes a short-lived perennial.

Flowers are reddish-purple, ½-1 inch wide. The bracts are narrow and tipped with a spine. Flowers are present June to September and grow singly or in small groups at the tips of branched stems.

Plumeless thistle reproduces by seed. The seeds lack a pappus.

Plants have taproots and can grow to 8 feet tall. Stems are winged and branch towards the ends. Leaves are dark green with a lighter midrib. The undersides of the leaves are hairy.

Rosettes form in the first year and bolt early in May to June of the next year. The rosette leaves are deeply lobed and spiney.

Plumeless thistle is found in disturbed areas, such as overgrazed pastures, rangelands, roadsides, and rights-of-way.

Originally from Eurasia, it has been known in the northeast US since 1837 and in Colorado since the mid-1950s.


MN Dept. of Agriculture

WASHINGTON STATE Noxious Weed Control Board


Rosette – Loke T. Kok, Virginia Polytechnic Institute and State University, Bugwood.org
Stem – Steven Katovich, Bugwood.org
All others: Jeffco Invasive Species Management

Items of Interest

Weed of the Month


January Weed Profile – Common Mullein

February Weed Profile – Cypress Spurge

March Weed Profile – Dames Rocket

April Weed Profile – Sulfur Cinquefoil

May Weed Profile – Poison Hemlock

June Weed Profile – Plumeless Thistle


January Weed Profile – Knotweed

February Weed Profile – Rush Skeletonweed

March Weed Profile – Black Henbane

April Weed Profile – Chinese clematis

May Weed Profile – Houndstongue

June Weed Profile – Milk Thistle

July Weed Profile – Oxeye Daisy

August Weed Profile – Spotted Knapweed

September Weed Profile – Perennial Pepperweed

October Weed Profile – Yellow Flag Iris

November Weed Profile – Common St. Johns Wart

December Weed Profile – Field Bindweed


January Weed Profile – Dalmatian Toadflax

February Weed Profile – Common Mulllein

March Weed Profile – Mediterranean Sage

April Weed Profile – Saltcedar

May Weed Profile – Absinth Wormwood 

June Weed Profile – Eurasian watermilfoil 

July Weed Profile – Yellow starthistle 

August Weed Profile – Hairy willowherb

September Weed Profile – Yellow toadflax

October Weed Profile – Chamomile

November Weed Profile – Diffuse knapweed

December Weed Profile – Poison hemlock


January Weed Profile – Cheatgrass

February Weed Profile – Myrtle Spurge

March Weed Profile – Hoary Cress

April Weed Profile – Leafy Spurge

May Weed Profile – Scotch Thistle

June Weed Profile – Dyer’s Woad

July Weed Profile – Orange Hawkweed

August Weed Profile – Purple Loosestrife

September Weed Profile – Teasel

October Weed Profile – Canada Thistle

November Weed Profile – Russian Knapweed

December Weed Profile – Russian Olive