Carduus acanthoides L.

Growth Form

Carduus acanthoides L. may grow over 2 metres (6.6 ft) tall, and can form weedy stands made up of just this species. Its stem and foliage are spiny, and sometimes woolly.

Etymology

The specific epithet acanthoides refers to the plant’s spiny foliage.

Growth Stages

This species starts growth as a flat basal rosette, then sends up an erect stem that bears occasional toothed, wrinkled, spiny leaves.

Leaf Dimensions

The leaves are 10–20 cm (4–8 in) long, with lobed or pinnately divided edges.

Leaf Surface

The abaxial (underside) surface of the leaf is somewhat hairy.

Inflorescence Arrangement

At the tip of each stem branch sits an inflorescence holding one to several flower heads.

Flower Head Characteristics

Each flower head is rounded, covered in spiny phyllaries, and bears many threadlike purple or pink disc florets. Each flower head measures around 13–25 mm (0.5–1 in) across.

Flowering Period

This plant flowers throughout summer and early fall.

Achene Characteristics

Its achenes are 2–3 mm long, four-angled, and marked with faint lengthwise stripes.

Pappus Characteristics

Its fluffy pappus bristles are 11–13 mm long.

Life Cycle

After flowering and producing seed, the plant dies.

Native Range

Carduus acanthoides is native to an area extending from France, Italy, and western Turkey, through Russia and Kazakhstan, to China.

Native Habitat

Within its native range, it grows in open grasslands and disturbed areas.

Non-Native Habitat

In non-native ranges, it grows as a weed in annual grasslands, roadsides, fields, pastures, and disturbed areas.

North American Status

It has been widely introduced across much of North America, where it is sometimes considered a noxious weed or invasive species.

California Control Program

The California Department of Food and Agriculture runs an active program to control known populations of this plant.

Dispersal Mechanism

It spreads via its seeds; each individual plant produces around 1,000 seeds.

Ecological Benefit

However, the plant has beneficial impacts on native bees in North America.

Chicago Region Occurrence

Although it was first recorded in the Chicago region in 1962, it has not been seen there since 1985.

Midwest Habitat

In Michigan and Wisconsin, it does not grow in undisturbed remnant native habitats, and instead occurs in sites with a history of disturbance, such as railroad right-of-ways, roadsides, and farm fields.