History of the introduction and spread of St. John's wort (Hypericum perforatum L.) in Australia
J.A. HarrisA and A.M. GillB
A Faculty of Applied Science, University of Canberra, PO Box 1, Belconnen, ACT 2616, Australia.
B CSIRO Division of Plant Industry, GPO Box 1600, Canberra, ACT 2601, Australia.
Hypericum perforatum has been introduced into Australia a number of times, the first being more than 100 years ago. It was cultivated in the Melbourne and Adelaide Botanic Gardens in 1858 and 1859, respectively, for potential use in home gardens. The earliest recorded outbreak of the wort was in 1880 at Bright, Victoria; i.e. escaped from a local garden where it was planted for medicinal purposes. Another outbreak occurred at Coromandel Valley in the Adelaide hills, possibly as early as 1881, and certainly by 1886. The earliest outbreak in New South Wales seems to have occurred at Mudgee in 1890 from either horse fodder or as a 'garden escape'. It now occurs in all States. Herbarium records suggest that its range was still increasing in the 1980s. Today it is still abundant in some localities, particularly in south-eastern Australia. For example, in 1986, 200 000ha of the Tablelands of New South Wales were heavily infested with the wort.
The pattern of spread of St. John's wort has consisted of increasing numbers of isolated occurrences from which expansion has occurred until they coalesced. Spread rate was most rapid, perhaps through the accidental movement of seed associated with the movement of stock and their fodder, as well as through 'garden escapes' following deliberate plantings for horticultural use.
Initially an agricultural problem, it is now more of a problem along roadsides and easements and in non-agricultural land, generally. Low levels of disturbance, such as mowing-burning-scarifying increased populations whereas frequent, intensive disturbance such as repeated ploughing used in tobacco cultivation, eliminated it. Population explosions could well be attributed to a changed disturbance regime in a locality, and/or seed longevity. That seeds may lie dormant in the soil for many decades underscores the ability of the species to 'return' to a site after a prolonged absence (such as under pine plantations) and to some extent independent of the cause of that absence.
Plant Protection Quarterly (1997) 12 (2) 52-56.