Weed Alert: Hawkweed
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|Orange hawkweed - weed management guide (617 kb, PDF)|
- Declared in NSW under the Noxious Weeds Act 1993 (Current Status)
- National Environmental Alert List Weed (definition)
Contacts and Further InformationIf you find this weed please help to prevent its further spread by contacting your local Council Weeds Officer or the nearest NSW Department of Primary Industries office immediately for positive identification and further assistance.
Alternatively call the NSW Weeds Hotline on
1800 680 244 or send an email to firstname.lastname@example.org
Hawkweeds (Hieracium species)
Hawkweeds have the potential to be serious weeds in the temperate areas of south-eastern Australia, including the Australian Alps and Tasmanian grasslands. Prompt treatment of known populations of hawkweeds has limited their spread so far.
Hawkweeds are highly invasive plants forming dense stands of up to 3800 plants per square metre. This is a major threat to biodiversity in conservation areas and native grasslands. Hawkweeds can also be a problem in pastures, on roadsides and in gardens. They are frost-tolerant and competitive across a wide range of soil types, preferring cool climates with an annual rainfall above 500 mm.
The genus Hieracium includes several hundred species known as hawkweeds. Hawkweeds belong to the Asteraceae or daisy family and were promoted as cottage garden plants. Hawkweed plants were previously sold by nurseries and these are likely to be sources of further infestations.
Four Hieracium species are known to occur in Australia. These include orange hawkweed (Hieracium aurantiacum) in Victoria and New South Wales (NSW); king devil hawkweed (Hieracium praealtum) in Victoria; and wall hawkweed (Hieracium murorum) in NSW. Small infestations have been found around ski fields where seed was introduced on equipment from New Zealand. A small population of mouse ear hawkweed (Hieracium pilosella) was found in Tasmania in 2001.
Hawkweeds are native to the northern hemisphere, South Africa and South America. Several European species have become major weeds of pastures, gardens and natural areas in eastern North America, Japan, Patagonia and New Zealand.
Hawkweed can reproduce and spread both by seed and vegetatively. Vegetative spread of plants by rhizomes (underground stems) and stolons (above ground rooting stems) is common. Stolons arise from buds at the base of the leaves.
Up to 40 000 seeds per square metre are produced in summer. Seeds have tufts that enable them to attach to hair, fur and vehicles. Seed can also be spread by wind, water, in contaminated fodder and garden waste, and even on ski or hiking equipment. The seeds can survive in the soil for many years.
Hawkweed seed usually germinates in spring after rain. Seedlings establish readily on bare soil and disturbed areas.
The general appearance of a hawkweed plant is similar to a dandelion (Taraxacum officinale) or a flatweed (Hypochaeris species). Hawkweeds are perennial herbs of variable height (15–40 cm), and have a milky sap which is seen when their stems or leaves are broken.
Key identification features
- Leaves are stalkless, hairy on both surfaces, with smooth or slightly toothed margins and are sometimes ‘sticky’ to touch. They occur in rosettes. Occasionally 2–4 alternate leaves appear near the base of the upright flower stem.
- Flowers are yellow, orange or red and ‘daisy-like’. They may be solitary or formed in a cluster of 5 to 30 flower heads. The flowers are 10–20 mm in diameter with square-ended petals, and grow on stems up to 40 cm. The flower stems are covered in short, stiff hairs.
- Seeds are purplish-black and ribbed with a bristly tuft up to 6 mm long.
Contact your local council weeds officer for assistance if you suspect you have found hawkweed. A combination of manual removal and herbicides can be used to control hawkweed, but care must be taken to ensure plants are not spread during control, and that follow up control is carried out for many years. Competitive, well managed pastures help to reduce the size and impact of infestations.
Hawkweeds are Class 1 State Prohibited Weeds across NSW under the Noxious Weeds Act 1993. They must be eradicated and land must be kept free of the plants. As notifiable weeds, all outbreaks must be reported to the local council within 24 hours, and the plants are prohibited from sale in NSW.
2008 edition prepared by Annie Johnson; 2012 edition prepared by Elissa van Oosterhout; Reviewed by Scott Charlton, Andrew Storrie and Birgitte Verbeek.
- Hawkweeds Agfact (2005) NSW DPI; Orange Hawkweed Weed Management Guide (2003) CRC for Weed Management
- Williams NSG and Holland KD (2007) The ecology and invasion history of hawkweeds (Hieracium species) in Australia, Plant Protection Quarterly, 22(2): 76-80