Photo guide to weeds

Bitter weed (Helenium amarum)

  • Bitter weed plant
    Bitter weed infestation
  • Bitter weed flower
    Bitter weed flower

General information

Bitter weed is an annual plant, native to south-eastern United States and Mexico. Bitter weed is poisonous to livestock. Found in Mt Tamapara area of Queensland was treated and believed to be eradicated until it came back ten years later.

Bitter weed is not a declared pest under Queensland legislation. 

Overview

Scientific name Helenium amarum
Description
  • Herb, annual up to 60cm high. Compact and bushy under favourable conditions
  • Smooth branching stems, numerous smooth leaves
  • Leaves are narrow thread-like, light green to gray blue.
  • Flowers are yellow daisy-like about 2cm in diameter.
  • Unnoticed when competing with other plants, producing a single flower on plants as small as 5cm tall.
Habitat
  • Prefers open fields, roadsides and waste places in subhumid, warm temperate and subtropical areas where annual rainfall does not exceed 1000mm.
Distribution
  • Native to North and South America.
  • Only known to exist at a single location near Mt Tarampa in South East Queensland.
Life cycle
  • Most flowering occurs over spring and summer.
  • Mature seeds are non-dormant and germinate readily in sunlight.
  • Scented flowers are pollinated by insects such as bees and butterflies.
Spread
  • Seeds in hay, silage and on vehicles
Impacts

Environmental

  • Competes with native vegetation.

Economic

  • Potential weed of pastures
  • Poisonous to stock including sheep, horses and cattle.
  • Taints milk of dairy cattle.
Prevention

The best form of weed control is prevention. Treat weed infestations when they are small - do not allow weeds to establish.
Ways to prevent weed spread 

Control

Physical control

  • Hand removal ensure all root system is pulled up.

Herbicide control

  • Broad-leaf herbicides such as 2,4-D or Grazon P+D® can be effective.

Biological control

  • There is no biological control agent available for this plant.
Declaration details
  • not a declared species under Queensland legislation but may be declared under local government law

Last updated 24 February 2014