Weed profile: Orange hawkweed

by admin on January 13, 2011

Orange hawkweed flower stem (Photo: DPIPWE)

Orange hawkweed (Hieracium aurantiacum) is on the Australian Alert List for Environmental Weeds, a list of 28 non-native plants that threaten biodiversity and cause other environmental damage.

These weeds are in their early stage of establishment, however they have the potential to seriously degrade Australia’s ecosystems.

Orange hawkweed is also declared under the Tasmanian Weed Management Act 1999.

It was probably introduced into Tasmania’s Central Highlands as a garden plant early in the 20th century but was not recorded in mainland Australia until much later.

Orange hawkweed can reproduce by seeds and stolons. Plants usually produce 4-8 stolons. (Photo: DPIPWE)

Currently it is found at a limited number of sites within Southern Tasmania, including outlying infestations in the Derwent Bridge/WHA area and at Sandy Bay, Taroona, Snug and Kingston as well as old records from plantings in Hydro villages on the Central Plateau including Miena and Shannon. The main or ‘core’ infestation is in the Fern Tree/Neika area.

Orange hawkweed is a native of the mountains of northern and central Europe. It is a perennial plant that grows up to 40cm high and has bright orange flowers and hairy stems and leaves.

The lance-shaped leaves form a basal rosette with the flower stem rising up like a dandelion. Leaves are 100-150mm long, dark green on the upper surface and light green underneath, and form rosettes close to the ground.

Each flowering shoot consists of 5-30 flower heads, 10-20mm in diameter. The orange flowers, with square-edged petals, make flowering plants easy to identify. It flowers from December to January and reproduces primarily by runners or stolons (stems that lie horizontally on the ground).

If not flowering, the presence of runners and short black hairs on stems and leaves will help identify this species.

Seeding is important for more widespread dispersal. Minute barbs along ribs on the seeds enable them to stick to hair, fur, feathers, clothing and vehicle, and be carried long distances. Seeds can be dispersed by wind and water, and in dumped garden waste and contaminated soil.

Orange hawkweed invades disturbed areas (eg, roadsides, drains, residential areas), ski fields, grasslands, pastures and alpine meadows. It has also spread into open woodland in Tasmania and Victoria.

Orange hawkweed flowers (Photo: © Canadian Nature)

This weed has been targeted in the Fern Tree area for the past four years by Hobart City Council and in the Derwent Park area for the past six years by Parks & Wildlife Service, Lake St Claire.

Hobart City Council has controlled all known infestations along their roadsides each year and encouraged landholders to control plants on their land.

The STCA have recently received Australian Government Caring for our Country funding for the next three years to support landholders to control their infestations with the aim of eradicating all outliers, protecting Wellington Park and preventing its spread into other areas.

If allowed to spread this weed will be highly detrimental to Tasmania’s economy and environment. It is a serious invader of alpine and highland lakes areas on the mainland including Kosciuszko National Park in New South Wales and Falls Creek in the Victorian high country.

It closely resembles the common lawn weeds dandelion and hawkbit, but is far more invasive and can dominate pasture and native grasslands, excluding native vegetation. The plant sends out stolons (suckers) and its light seeds can be blown many kilometers, so that even a single plant poses significant risk.

Please report all plants to the STCA Weeds Project Manager Sandy Leighton HYPERLINK “mailto:sleighton@stca.tas.gov.au” sleighton@stca.tas.gov.au or phone 0437 450 143.

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