knot-grass

A small bird perches on a clump of knot-grass.

Definition

1. Noun:
   • A common name for several species of plants in the genus Polygonum (now often placed in Persicaria), characterized by jointed stems and small, often pink or white flowers. These plants are typically found in disturbed areas, such as roadsides and gardens, and are known for their creeping or mat-forming growth habit.
   • Specifically, it often refers to Polygonum aviculare (prostrate knotweed), a low-growing annual weed with narrow leaves and tiny flowers that grows in compacted soil.

Usage Examples

• (A weed with jointed stems.)
• (A plant used in folk medicine.)

Advanced Usage

• "to be as common as knot-grass": an archaic or regional phrase meaning to be very abundant or widespread.
  • In that neglected field, knot-grass was as common as dandelions. (The weed was extremely plentiful.)

Variants and Related Words

• Knotweed (n): a related plant from the same genus, often used interchangeably with knot-grass in some contexts, but typically referring to larger species like Japanese knotweed ().
  • The invasive knotweed choked out the native plants. (A larger, aggressive relative of knot-grass.)

Synonyms

• Prostrate knotweed: a common name for .
• Birdweed: a folk name for knot-grass, as birds eat its seeds.
• Wireweed: another name referring to its tough, wiry stems.

Related Idioms

• "knot-grass in the garden": a metaphor for a persistent or unwanted problem.
  • His bad habit was like knot-grass in the garden — hard to remove once established. (A persistent nuisance.)