(Hieracium (syn.
Pilosella) species)
Note: orange hawkweed
Hieracium aurantiacum is now
Pilosella aurantiaca subsp.
aurantiaca
What is hawkweed?
There are a number of introduced hawkweed species which are potential weeds in Tasmania.
Hawkweed is a weed of native grasslands and pastures.
Hawkweed is a
declared weed in Tasmania under the Tasmanian Biosecurity Act 2019 and associated Regulations. The importation, sale and distribution of hawkweed are prohibited in Tasmania.
How to identify hawkweed
Hawkweeds are perennial (long-lived) herbs belonging to the daisy family.
Orange hawkweed stems grow to 40 cm high and have numerous blackish hairs. The flowers are bright orange and daisy-like while the leaves occur as a rosette (or whorl) at the base of the plant and are also hairy. Leaves usually grow at a slight angle to the ground but under grazing pressure and harsh conditions they lie flat.
Seed germinates throughout the growing season, especially in autumn. Plants grow rapidly and usually flower within the first growing season, but flowering may be delayed in late germinating plants. Seedlings establish readily on bare areas.
Orange hawkweed plants produce between four and eight leafy runners (called stolons) that can reach lengths of 25 cm. Runners grow from buds in the rosette when the plants are flowering. These runners form new rosettes so that a patch continues to expand until it covers the site with a solid mat of hawkweed.
Hawkweed flowers, © Louis-M Landry.
Hawkweed infestation, © Louis-M Landry.
Hawkweed in Tasmania
Two species of hawkweed have been recorded in Tasmania: orange hawkweed Pilosella aurantiaca (syn.
Hieracium aurantiacum)
has naturalised at several sites, while mouse-ear hawkweed Pilosella officinarum (syn.
Hieracium pilosella) established at one site but has now been eradicated.
Hawkweed has been found in open woodland and grasslands, poor pastures, roadsides and neglected areas in the Southern Midlands, Central Highlands and around Hobart. Hawkweed is also occasionally found in the ornamental and herbal plant trade.
Hawkweed colonises spaces between tussock grasses, often in higher altitude areas, and can be extremely invasive. Heavy infestations form large swards which prevent regeneration and survival of native species and reduce productivity in grazing areas.
What is the legal status of hawkweed in your area?
Detailed management and control guidelines for hawkweed can be found in the Hawkweed Control Guide. Refer also to
Herbicides for Hawkweed Control. For further information see Weed Links and Resources.
See also
Other useful links
Hawkweed 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;
Carefully time your use of herbicide for best results (see the
Herbicides for Hawkweed 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 hawkweed to hawkweed-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 hawkweed 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 hawkweed
Orange hawkweed spreads by runners over short distances and by seed over larger areas.
Seeds have minute barbs which enable them to stick to hair, fur, feathers, clothing and vehicles, and be carried long distances.
Seeds can be dispersed by wind and water, and in dumped garden waste and contaminated soil. They may also be spread by snow clearing and road maintenance machinery.
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 hawkweed.
Physical removal
Small infestations of hawkweed can be removed by digging out the shallow-rooted rosettes.
Ensure the whole plant, including all roots and runners, are removed, as plants quickly regrow from fragments if any pieces of runners or roots are left behind.
Be careful when removing flowers and seedheads so that seeds are not accidentally dispersed. Flower and seedhead material should be burned.
Mowing can prevent seed production by removing flowering stems. However repeated mowing can stimulate growth of runners and worsen an infestation.
Cultivation
Establishing a competitive, well managed pasture or lawn area can reduce the size and impact of hawkweed infestations.
On cropping land, establishing a competitive crop can control hawkweed, especially where herbicides are also used in the cropping system.
Chemical control
Herbicides for Hawkweed Control
Herbicides for Hawkweed Control
Important Disclaimer
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