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Weed Identification

musk thistle

Family

Asteraceae

Scientific Name

Carduus nutans

Other Common Names:

plumeless thistle
plumeless thistle
plumeless thistle

Synonyms (former Scientific Names):

Carduus macrocephalus
Carduus nutans
Carduus macrolepis

Habit

This erect biennial can be found flowering from mid spring into early summer.

Leaves

The leaves initially form a basal rosette, however in the second year the flowering stem emerges, and the leaves on the stem will grow in an alternate fashion. The individual leaves are deeply lobed with 1 to 5 spines at the tip. All leaves are dark green with white veins, and progressively get smaller as you move up the plant.

Identifying Characteristics

This plant produces a musky scent, giving it its name.

Flower Seed Head

The solitary flowers grow at the ends of branches. Each pink or violet flower has purple tinged spiny bracts below it.

Seed Fruit

The seeds develop in a brownish oblong achene. Each achene has a white pappus that resembles small hairs.

Where Found

This plant can be found along roadsides and other disturbed areas

Growth Habit

Varies: 
upright and nonwoody
prostrate and nonwoody

Thorns or Spines

present

Approximate Flower Diameter

Varies: 
half dollar
larger

Dominant Flower Color

Varies: 
yellow
purple
pink

Flower Symmetry

radial symmetery

Leaf Hairs

has hairs

Leaf Shape

Varies: 
lance
oval
spatulate

Leaf Arrangement

alternate

Leaf Margin

Varies: 
lobed
serrated

Leaf Structure

simple

Leaf Stalk

none

Stem Hairs

no hairs

Stem Cross Section

round or oval

Milky Sap

not present

Root Structure

taproot

Life Cycle

biennial

Ochrea

not present

Plant Type

Herb