Definition

Noun A Mediterranean annual or biennial herb (genus Centaurea, especially Centaurea calcitrapa and related species) characterized by pinkish to purple flowers that are surrounded by spiny, scale-like bracts. It has become naturalized in parts of America.

Usage

The term "star-thistle" is used as a common name for specific, spiny herbaceous plants, primarily within botanical, agricultural, or ecological contexts. It refers to the plant's physical appearance, notably its star-like arrangement of spines.

Examples

• The pasture was overrun with star-thistle, making it difficult for the livestock to graze.
• Botanists are studying the spread of the invasive star-thistle in California.
• The star-thistle is easily identified by its distinctive purple flowers and sharp, radiating spines.

Advanced Usage

• As a modifier: The term can be used attributively to describe related concepts.
  • Example: The county has a star-thistle control program to manage the invasive species.

Variants and Related Words

• Yellow star-thistle (): A specific and highly invasive species with yellow flowers, often simply called "star-thistle" in regions where it is prevalent.
• Barnaby's star-thistle (): Another common name for yellow star-thistle.
• Calcitrap (): A historical name for a common type of star-thistle, derived from its spiny, trap-like flower heads.

Synonyms

• Caltrop (This name is shared with other spiny plants and a metal weapon, but can refer to ).
• Knapweed (A related genus, , includes plants sometimes called star-thistles, though not all knapweeds have the same pronounced spines).

Notes

• Caution: "Star-thistle" is not a true thistle (genus or ), but is named for its similar spiny appearance. It is a member of the aster family (Asteraceae).
• The plant is often considered a noxious weed in its naturalized range due to its invasiveness and the danger its spines pose to animals and humans.

Noun

1. Mediterranean annual or biennial herb having pinkish to purple flowers surrounded by spine-tipped scales; naturalized in America