St. John's wort is a perennial herb with two distinct growth phases, a fall/winter prostrate or basal growth, and a spring/summer erect woody stem growth (Gordon & Kluge, 1991). St. John's wort has an underground rhizomatous stem and deep taproot with many lateral roots (Krueger & Sheley, 2002). The erect vegetative growth has opposite, sessile, entire (ANHP, 2005), linear to elliptical leaves 10-30mm long and 3-16mm wide, with translucent glands located on the undersides of the leaf and black glands located along the leaf margins (PIER, 2003). The flowers are numerous, paniculate cymes with 5 yellow petals, 5-8mm long, black dotted along the margins as well (PIER, 2003). Multiple stamens cluster into three groups, with three styles present (PIER, 2003). The capsules are 7-8mm long, dark brown ovoid, three chambered (ANHP, 2005), holding thousands of small, pitted cylindrical seeds (PIER, 2003).

St. John's wort initiates new erect stem growth and seed germination in spring (Tisdale et al.1959). Mean germination temperature needs to be above 11°C and access to light and adequate precipitation (Tisdale et al. 1959). Seed exhibits dormancy from exudation from the leaves and capsules (Tisdale et al. 1959), with a time of 4-6 months after harvest before germination (ANHP, 2005). Seed can remain viable in the soil between 6-10 years (Tisdale et al. 1959). Flower production occurs in the summer with leaves beginning to shed near the end of the flowering period, late summer to fall (Tisdale et al. 1959). Seeds are shed in fall and shoots begin to dieback in the winter (Fox et al. 1999); however basal growth can occur during the winter as well (Tisdale et al. 1959). The plant is a perennial reaching maturity in two seasons, with the first years growth directed mainly to establishment of the root system (Tisdale et al.1959).

St. John's wort has become popular in the 1990s as a herbal remedy, mainly for the treatment of depression. In preliminary clinical studies 50%-80% of people suffering from mild to moderate depression showed improvement (Rey & Walter, 1998). Other potential medical applications using St. John's wort includes treatments for anxiety, sleep disorders, bacterial and viral infections, inflammatory arthritis, skin wounds, cancer, and certain respiratory conditions (Rey & Walter, 1998). The plant is collected from the wild, but with its increasing popularity, it has begun to be cultivated. In Russia the plant is also used to flavour a traditional soft drink, \"Baikal\" (Kireeva et al. 1999).

Hypericum perforatum forms dense stands on recently disturbed sites from impacts like mining, fire, logging, construction, etc. (Tisdale et al. 1959). It also establishes itself in waste grounds, roadsides, pasture, rangeland, and open woodland (Buckley et al. 2003). It has adapted to a wide range of environmental conditions in its native and introduced range (Maron et al. 2004). H. perforatum can tolerate a variety of soils, from dry, rocky, shallow soils, to deep fertile soils, with it performing best in regions with greater than 760mm of precipitation a year (Buckley et al. 2003). Soil pH tolerance ranges from 4.3-7.6 (ANHP, 2005). It can tolerate drought and disturbance conditions by storing reserves in its root crown (Buckley et al. 2003).

Hypericum perforatum reproduces through flower and seed production, as well as vegetatively through suckers arising from an underground rhizome (Tisdale et al. 1959). Flower production occurs in the summer with capsules persisting from late summer to early fall when seeds are shed (Fox et al. 1999). Seed production is very high with an average infloresence producing 39,000 seeds (Gordon & Kluge, 1991). Suckers can arise from the parent plant typically after mechanical damage or disturbance and quickly separate previous connections to the parent plant (Tisdale et al. 1959).

Hypericum perforatum was introduced into Australia in the middle of the 19th century for its ornamental and medicinal properties (Briese & Jupp, 1995).St. John's wort was introduced into South Africa in 1942 from a contaminated batch of vetch seed (Gordon & Kluge, 1991).Seed capsules can adhere to vehicles transporting the seed long distances (Gordon & Kluge, 1991).

St. John's wort establishes itself on recently disturbed sites (Tisdale et al. 1959) and displaces and inhibits the settlement and establishment of native flora (Briese & Jupp, 1995). The plant contains two primary toxic compounds hypericin and hypericum red, which can cause photosensitivity in grazing livestock, leading to loss of weight and condition, even death in rare circumstances (Tisdale et al. 1959). The dried stems that are present during the fall and winter can pose as a fire hazard for forest and range lands (ANHP, 2005).

Chemical: Chemical control of St. John's wort has had mixed results depending on the management plan and location of application. In South Africa, the initial management plan was a chemical eradication, however this programme was suspended when it proved unsuccessful and too expensive (Gordon & Kluge, 1991). Similarly, a chemical control in British Colombia, Canada, also was uneffective in eradicating the plant (Gordon & Kluge, 1991). However several field studies and programmes were initiated that designed a chemical application management strategy in the foothills and pasture lands of South Australia. Several different chemical formulations were used, but the ones that proved most successful were a combination of 2,4-D + 2,2,-DPA, or a straight application of glyphosate (Campbell et al. 1975). Timing of the applications is crucial in the success of a chemical application, with an autumn spraying seeming to be most effective in Australia (Campbell et al. 1975). In addition the method of application and the composition of the infested area prerequisite the chemical used. In a study by Campbell et al. (1991) found that triclopyr + picloram in combination were not selective for just St. John's wort but also killed any nearby legumes. A boom and spot method for application was discovered to work best with these chemicals. For glyphosates an aerial application worked better, and was more selective to St. John's wort, however glyphosates did not perform well at warmer temperatures (Campbell et al. 1991). For the best coverage using an aerial application adjuvants, water carriers, and repetitive anuual sprayings are recommended (Campbell et al. 1991). Ammonium sulfamate has been shown in several studies to be an effective herbicide against woody stem plants and St. John's wort, with the added benefit of decomposing into a plant soluble fertilizer for native grasses (Allgaier, 1944).

Cultural: Cultural management of St. John's wort has been in the form of controlled grazing by livestock (Campbell et al. 1975) but only as an additional means of control to other methods like a chemical or biological programme. It also msut be taken into consideration that St. John's wort is toxic and can cause neurological and other health problems, even death, if consumed in high quantities by livestock (Buckley et al. 2003). Goats seem to be more tolerant to the toxic effects of St. John's wort than other types of livestock (Buckley et al. 2003). Ploughing and fallowing on arable lands follwed by subsequent sowing of perennial grasses and legumes is another method of control (Campbell et al.1975). Sowing of perennial grasses and legumes a few weeks after a chemical application can help in suppressing any reemergence (Buckley et al. 2003).

Physical: Mechanical removal is not recommended for this species as it can vegetatively reproduce from the rhizomatous root crown which can be quite extensive underground (Tisdale et al. 1959). Fire is not recommended as a means of control since the plant can persist from underground resource storage in its crown(Buckley et al. 2003) and then reproduce through suckers (Tisdale et al. 1959).