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TELEGRAPH WEED
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Distribution
Telegraph weed (Heterotheca grandiflora) or "sticky daisy" was first recorded in Australia in the Raymond Terrace-Newcastle region in central New South Wales. In this region it grows in pastures, along roadsides and in wastelands.
In the early 1990's telegraph weed was discovered on The Spit on the Gold Coast in south-eastern Queensland. This infestation has spread, particularly in recent years, and has become common along coastal roadsides and tracks and on sand dunes. It is steadily moving in a northern direction, due to prevailing south-easterly winds, and has since been found on South Stradbroke Island, Wavebreak Island and along the foreshore at Labrador. The infestations present in Queensland covered an area of about 300 hectares in total in 2005.
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Origin
Telegraph weed, a member of the daisy plant family (i.e. Asteraceae), is native to northern Mexico and the south-western parts of the USA (i.e. California, Arizona, Nevada and Utah). It has not yet become widely naturalised in other parts of the world, but is a relatively common weed of dry and disturbed areas in Hawaii.
Habitat
In Queensland telegraph weed is currently restricted to sandy soils in coastal districts and it tends to invade bare areas or locations where most of the natural vegetation has been disturbed or removed. It is most commonly found on sand dunes, hind-dunes and in nearby areas (where it generally grows along roadsides and tracks). However, in NSW telegraph weed also grows in pastures and wastelands and in Hawaii it grows in a wide range of habitats, including as a pioneer on old lava flows and in poor sandy soils.
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Impact
Telegraph weed is a short-lived (i.e. annual) plant that grows quickly and can form dense infestations, particularly in disturbed or bare areas. It is a prolific seed producer and its seeds are easily dispersed. In Queensland it has already shown a propensity to form dense colonies on sand dunes and beaches. These infestations pose a threat to the natural vegetation on beaches and foredunes, and the understorey biodiversity of coastal plant communities, and it has already invaded a National Park on South Stradbroke Island. It has the potential to spread to environmentally significant areas including Moreton, North Stradbroke and Fraser Islands if the current infestations are not controlled. Based on its distribution in Hawaii and NSW it also has the potential to spread to inland areas.
This species can also be very unsightly when growing along beaches, particularly after it has finished flowering, and dense stands up to 2 m high can be difficult to pass through. Tourism is very important in many of the locations that telegraph weed has already infested, and a decline in the health and aesthetic beauty of these beach areas may have negative impacts on this industry (and also cause displeasure to local residents that regularly use the beach).
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Description
Telegraph weed is a short-lived (i.e. annual or biennial) herb that gives of a strong odour (i.e. it is aromatic). It has an upright growth habit and can reach up to 2 m in height. During the early stages of growth it develops a basal rosette of leaves and a long taproot. As plants mature they produce a single main stem, or sometimes several stems, that are branched mainly towards the top of the plant.
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The stems and leaves of this species are densely hairy. Many of these hairs are sticky in nature (i.e. glandular), particularly towards the top of the plant, and because of this telegraph weed is often called "sticky daisy" in south-eastern Queensland. The stems are rather thick, almost round in cross-section, and are often somewhat striated in appearance.
The leaves (20-80 mm long and 8-35 mm wide) are relatively thick, and their shape varies depending on their position on the plant. The upper leaf surfaces are somewhat hairy while the lower leaf surfaces are usually more densely hairy, thereby giving them a paler appearance. The lowermost leaves are usually egg-shaped in outline (i.e. ovate) or oblong in shape with bluntly or sharply toothed (i.e. crenate or serrate) margins. These leaves are usually borne on distinct stalks 10-40 mm long (i.e. they are petiolate).
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Leaves along the middle portion of the stems are usually somewhat narrower (i.e. ovate to oblanceolate) and have more deeply toothed margins (i.e. they are coarsely serrate). These leaves tend to be somewhat stalkless (i.e. sessile) and often widen to a pair of lobes at their bases.
The uppermost leaves are narrower again (i.e. oblanceolate to lanceolate), significantly smaller, have more sharply pointed tips, and usually have entire margins.
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The numerous small daisy-like flower-heads are borne at the tips of the branches, and are mostly produced during late summer. These flower-heads are 15-22 mm across and are bright yellow in colour. Each flower-head it actually made up of numerous smaller flowers (called florets) and has several rows of narrow green bracts at its base that form a cup-like structure (called an involucre). These bracts are 7-9 mm long and are also covered in small sticky (i.e. glandular) hairs.
In the centre of each flower-head are numerous (50-60) small tubular yellow flowers (about 4 mm long) that are called 'disc' or 'tubular' florets. Around the edge of each flower-head are 25-35 petal-like flowers (4-8 mm long) that are known as 'ray' florets.
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Reproduction and Dispersal
Numerous seeds (called achenes) can be produced by each flower-head. Each of these tiny seeds are 2-5 mm long and topped with a pappus of several yellowish-brown to reddish coloured hairs (4-7 mm long). These hairs assist wind dispersal of the seeds, allowing them to be spread significant distances by sea breezes. Seeds are also known to be dispersed after becoming attached to clothing and shoes. They can probably also float on water and may be dispersed in mud.
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Legislation
This species is currently not declared in
Queensland or in any other states of Australia. However, efforts have been
made to control known outbreaks in Queensland. In particular, it has been the subject of a concerted
control program on South Stradbroke Island involving the Queensland
Department of Primary Industries and Fisheries (QDPI&F), the Queensland Parks
and Wildlife Service (QPWS) and the Gold Coast City Council.
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Further
Information
Pacific Island
Ecosystems at Risk (PIER), Plant threats to Pacific ecosystems:
http://www.hear.org/pier/species/heterotheca_grandiflora.htm. US
Department of Agriculture, Forest Service.
S. Csurhes and R. Edwards (1998). Potential environmental weeds in Australia: candidate species for preventative control. Queensland Department of Natural Resources.
PlantNET - New South Wales Flora Online: http://plantnet.rbgsyd.nsw.gov.au. The Plant Information Network System of the Royal Botanic Gardens & Domain Trust, Sydney Australia.
Environmental Weeds of Australia. DVD-ROM. Centre for Biological Information Technology (CBIT), The University of Queensland.
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Created by:
webmaster@wsq.org.au
for The Weed Society of Queensland Inc.
Last updated: 12 February 2010
