Family: Asteraceae
Heterotheca grandiflora (telegraph weed) is an annual or biennial herb native to arid coastal regions of North America, from California to northern Mexico. It produces large numbers of wind-dispersed seeds and is naturalized on all the main Hawaiian Islands, USA, as well as in coastal regions of both New South Wales and south-east Queensland, Australia. In Hawaii it invades dry, disturbed sites from near sea level to over 2200 m elevation, forming dense cover and competing with native plants species including the endangered Schiedea hawaiiensis. In Australia, it is considered a potential or emerging environmental threat that invades and dominates disturbed sites and is designated a Class 2 weed in Queensland.
High Risk Traits:
- Elevation range exceeds 2000 m, demonstrating environmental versatility
- Grows in tropical climates
- Naturalized in the Hawaiian Islands, Australia and possibly Japan
- A disturbance-adapted plant that may threaten certain endangered plant species in Hawaii
- Other species have become invasive
- Aromatic foliage deters browsing
- Able to form dense ground cover
- Reproduces by seed
- Self-compatible
- Able to reach maturity in 1-2 growing seasons
- Seeds dispersed by wind, gravity and secondarily by water, soil movement, attachment of seeds to clothing or animals, and other human activities
- Prolific seed production (densities unknown)
- Disk achenes not dormant, but ray achenes are dormant and may form a persistent seed bank (seed longevity unknown)
Low Risk Traits:
- Unarmed (no spines, thorns or burrs)
- Non-toxic
- Pollinator-plant
- Not reported to spread vegetatively
- Herbicides provide effective control
- Manual removal provides effective control
