Erect perennial, herb, 0.3-0.9 m high. Fl. yellow, Nov to Dec. Roadsides, pastures.
Alternative Names. Common St. John's Wort, Tipton's Weed, Klamath Weed, Goatweed.
General Biology. Growth form. Herb. Life form. Perennial. Reproduction. Primarily seed, also stem fragments, short rhizomes. Dispersal. Water, soil, machinery, animals (adhesion and ingestion), wind, contaminated hay or soil. Toxicity. Contains a toxin that causes dermatitis and photo-sensitivity in livestock. Seedbank persistence. 13+ years, with vaiblity declining from 7 years onwards. Fire response. Heat from fire stimulate germination of seed. Can resprout and sucker from deep rhizomes.
Notes. Forms dense stands where it displaces native plant species, reduces wildlife habitat, depletes soil moisture, and in late summer may increase the fire hazard. Original infestations are usually associated with disturbance. Exhibits a high degree of phenotypic and genotypic variation. Appears well-adapted to a wide variety of habitats and climate conditions. Seedlings do not tolerate high salinity, litter and competition. Mature plants will survive long periods of inundation and have deep, extensive root systems. Has two distinct growth phases: autumn/winter prostrate basal growth and spring/summer erect woody stem growth. Vegetatively reproduces from lateral roots and root crowns, stimulated by grazing, fire and defoliation. Self-pollinated and insect-pollinated. Capable of producing tens of thousands of seed annually. Seeds have 4-6 months of after-ripening, reach maximum germinability at 12 months and require bare soil, sunlight and/or heavy rain for germination. Reaches maturity in two seasons, with the first year's growth directed mainly to establishment of the root system. Declared plant in New South Wales and many parts of the United States. A number of forms, varieties and subspecies have been recognised and readily forms hybrids with other Hypericum species. A biocontrol program in Australia has been partly successful but work is still continuing.
Additional information. Origin. Europe, north Africa and western Asia. History of use/introduction. Ornamental, medicines, materials. Similar exotic species. Hypericum canariense, H. perforatum subsp. veronense. Similar native species. H. gramineum.
Suggested method of management and control. Spot spray at flowering (when half are in bud and the remaining half in open flowering, do not spray after half are in green bud) with Grazon® (triclopyr + picloram) 50 mL/10 L water. Glyphosate applied to germinants following autumn rains can be effective. Timing of applications is crucial. Repeated annual sprayings are recommended. Mechanical removal is not advised as plants resprout from extensive rhizomes. Read the manufacturers' labels and material safety data sheets before using herbicides. For further information consult the Australian Pesticides and Veterinary Medicines Authority to determine the status of permits for your situation or state.
Legend: Y = Yes, regularly, O = Occasionally, U = Uncertain, referred by others but not confirmed.