St John's wort in flower & infestation, © K Stewart, NRE Tas.
St John's wort in Tasmania
St John's wort occurs as a localised weed of roadsides, poorly managed grazing land, neglected areas and disturbed bushland areas of Tasmania, particularly in the northern Midlands, north-east, central north coast and the south east.
St John's wort is a threat to the grazing industry due to its toxicity to stock, and its ability to compete with desirable pasture species in poorly managed pastures.
St John's wort is also an environmental weed and can out-compete native species, with open grassland-woodland communities most affected.
Legal status of St John's wort in your area
The legal responsibilities of landholders and other stakeholders in dealing with St John's wort are laid out in the
Statutory Weed Management Plan for St John's Wort.
Use Table 1 (Zone A municipalities) in the Statutory Weed Management Plan to find out whether your area falls in an eradication or containment zone.
Detailed management and control guidelines for St John's wort can be found in the St John's Wort Control Guide. Refer also to
Herbicides for St John's Wort Control. For further information see Weed Links and Resources.
See also
St John's Wort Control Guide
Do
Plan your control program, this will save time and money in the long-run;
Consider the impact of your control methods on off-target species, especially if herbicides are used;
Ensure machinery and equipment is washed down between sites or prior to contractors leaving site;
Get in early - For new infestations, eradicate before the plants reach the flowering stage: once plants begin seeding, control becomes more difficult and expensive;
Carefully time your use of herbicide for best results (see
Herbicides for St John's Wort Control for more information);
Coordinate your control program with neighbouring landholders where your weed problem crosses property boundaries;
Revisit and regularly inspect the site and ensure follow-up is undertaken;
Use a combination of different control methods; and
Establish vigorous pasture (or native species) after removal to reduce re-infestation.
Don't
Don't introduce St John's wort to St John's wort-free areas (e.g. by failing to wash down machinery and equipment between sites);
Don't start your control program without first planning your approach;
Don't allow St John's wort to flower and set seed before treatment;
Don't rely on one attempt at removal - follow-up is essential;
Don't rely on just one control method.
Spread of St John's wort
St John's wort spreads by seed and by vegetative means (crown and rhizomes).
Seed is the main means of spread. A mature plant can produce between 15,000 and 30,000 seeds. St John's wort seed may remain viable for at least up to 20 years.
Seed is spread by wind, in water and soil, and as a contaminant of agricultural produce. The sticky capsule attaches to animal wool and fur, clothing and can also survive the digestive systems of most stock.
Cultivation, earthworks and roadside machinery can spread pieces of the crown or rhizomes to clean areas where the fragments produce new plants.
Avoid the introduction of St John's wort
Preventing the introduction of St John's wort to clean areas is the best means of control. Good hygiene practices are vital.
St John's wort is easy to identify when in flower, and small isolated infestations should be removed as soon as possible, preventing further spread.
See the
Washdown Guidelines for Weed and Disease Control for detailed information on how to wash-down equipment and personnel to reduce the chance of spreading St John's wort.
Physical removal
Isolated plants and small infestations can be removed by hand, preferably before seeding.
Remove as much of the root system as possible as St John's wort can sucker from roots left in the ground.
Follow-up will be required to deal with any further germination or suckering.
Cultivation
St John's wort can be set back by cultivation which exposes and dries out the roots, then sowing to pasture.
The developing pasture should be left un-grazed for the first year to allow the subterranean clover maximum chance to smother the St John's wort.
Over-grazing will favour the weed as it reduces the competition from the pasture plants.
Grazing programs need to be well planned and carefully managed to ensure stock do not suffer poisoning.
Burning
Burning should not be used to control St John's wort. Burning stimulates reshooting and suckering and can worsen an infestation.
Chemical control
A number of herbicides are registered for use on St John's wort in Tasmania. See
Herbicides for St John's Wort Control for more information.
Herbicides for St John's Wort Control
Herbicides for St John's Wort Control
Important Disclaimer
To the extent permitted by law, the Department of Natural Resources and Environment Tasmania (including its employees and consultants) excludes all liability to any person for any consequences, including but not limited to all losses, damages, costs, expenses and any other compensation, arising directly or indirectly from using information or material (in part or in whole) contained on this website.