76 Plant Protection Quarterly Vol.22(2) 2007 H. praealtum, H. pilosella and H. murorum. The morphology of each species is briefl y The ecology and invasion history of hawkweeds described below and the available infor- mation on their invasion history in Aus- (Hieracium species) in Australia tralia provided. Detailed species descrip- tions can be found in Webb et al. (1988). N.S.G. Williams and K.D. Holland The genus Hieracium is commonly split Australian Research Centre for Urban Ecology, Royal Botanic Gardens into two groups: the stoloniferous spe- Melbourne, c/o School of Botany, The University of Melbourne, Victoria 3010, cies (i.e., possessing ‘runners’), known Australia. Email: [email protected] as the Pilosella group, and a larger group of non-stoloniferous species (Hieracium sensu stricto), which includes H. murorum (Makepeace 1985a, Webb et al. 1988). Pi- Abstract Four Hieracium spp. are naturalized in losella contains approximately seventy Hawkweeds (Hieracium spp.) are peren- Australia, and pose a substantial threat to species, and includes most of the hawk- nial herbs that are serious environmental agriculture and the environment. Quaran- weeds that are considered weeds world- and agricultural weeds in many temperate tine regulations now prohibit importation wide (Makepeace 1985a), including H. and subalpine areas of the world. In Aus- of hawkweeds into Australia (National aurantiacum, H. pilosella and H. praealtum tralia, they are recognized as a signifi cant Heritage Trust 2003, NSW Department (Webb et al. 1988). threat and their importation is now pro- of Primary Industries 2005) and they are hibited. However, four Hieracium species listed as noxious weeds in Victoria, New Hieracium aurantiacum L. (orange are already naturalized. It is believed that South Wales and Tasmania (National Her- hawkweed) populations of H. pilosella may no longer itage Trust 2003). Despite this, they are Hieracium aurantiacum has a basal rosette persist, while efforts to control H. auran- still sometimes sold to gardeners (Blood of leaves and a single stem 15–40 cm tall. tiacum, H. praealtum and H. murorum 2004, Morgan 2000) and may be found in Plants produce bright, red-orange fl ower- are continuing. This paper reviews the wildfl ower seed mixes (National Heritage heads in clusters of 5–15 heads at the top invasion history of known infestations in Trust 2003). of the stem (Webb et al. 1988). In Australia, Australia, as well as the general biology Climatic modelling suggests hawkweeds H. aurantiacum fl owers from January to and ecology of invasive hawkweeds. could spread across large areas of the high March, making plants most conspicuous rainfall regions of mainland south-eastern at this time (National Heritage Trust 2003). Introduction Australia and Tasmania. For example, ap- The species is also known as Pilosella au- Hawkweeds are perennial herbs of the proximately 270 000 km2 of land is consid- rantiaca (L.) F.W.Schultz & Sch.Bip. (Blood large northern hemisphere genus Hier- ered potentially at risk from H. aurantiacum 2001, Webb et al. 1988), and is native to acium (Asteraceae). They show enormous (Cunningham et al. 2003). Potential produc- mountains of northern and central Europe phenotypic variability, resulting in many tion losses in grazing areas are conserva- (Morgan 2000, Webb et al. 1988) where it subspecies, varieties and forms (Mráz and tively estimated at $74 million (Brinkley occurs primarily in meadows and hillsides Szelag 2004, Zidorn et al. 2002). Conse- and Bomford 2002). However, Hieracium (Wilson and Callihan 1999). In Australia, quently, the taxonomy of the group and spp. have also been identifi ed as ‘sleeper H. aurantiacum subsp. carpathicola Nägeli number of species is debated (Coskunçelebi weeds’ (Brinkley and Bomford 2002). & Peter has been found naturalized in Tas- 2003). This is thought to be due to frequent Sleeper weeds pose a serious threat but are mania, Victoria and New South Wales, and hybridization events during the evolution currently in the early stages of establish- has been collected from a garden in Perth. of the group (Mráz and Szelag 2005). Over ment and have a limited distribution. Early 9000 Hieracium species have been pro- eradication may therefore be highly cost Tasmania posed or recognized (Strother 1997), some effective (Brinkley and Bomford 2002). The largest populations of H. aurantiacum of which are serious environmental and This paper reviews the biology and in Australia occur in Tasmania, scattered agricultural weeds. ecology of invasive Hieracium spp. and throughout the Central Highlands and Once established, some hawkweeds documents the invasion history of known Southern Midlands (Figure 1). The spe- spread rapidly by stolons and rhizomes, naturalized species in Australia. By doing cies is thought to have initially escaped forming dense mats of plants that out- so, we hope to raise awareness of invasive from gardens in towns associated with compete other species, lowering biodiver- hawkweeds and provide weed managers hydroelectricity schemes (Andrew Crane sity and reducing forage value of pastures with information that may assist control personal communication). The largest in- (Rinella and Shelley 2002). They are of and eradication of infestations. Records of festation is in the Hobart suburb Fern Tree, concern in many countries due to their in- Hieracium spp. were obtained from her- on the foothills of Mt. Wellington, where it vasiveness and impact. In New Zealand, baria in Melbourne, Sydney, Canberra, established before 1963 (National Heritage Hieracium spp. dominate the vegetation Hobart, Perth and Adelaide. Further data Trust 2003). Mapping shows the popula- on more than 500 000 ha of the South Is- and detailed invasion histories of Hi- tion expanded down-slope due to seed land, threatening viability of the pastoral eracium spp. in Australia were obtained dispersal via wind and watercourses, and industry and conservation values of native through discussions with weed experts is now spread over 500 ha. It is thought tussock grasslands (Duncan et al. 1997). At and land managers in state government that slashing roadsides also spreads the least ten hawkweed species are natural- departments and agencies around Aus- species, including to one site at Snug, 20 ized in New Zealand (Webb et al. 1988) tralia. Information on the ecology of inva- km from the nearest known population after arriving in the mid-1800s in con- sive Hieracium spp. was obtained through (National Heritage Trust 2003) and other taminated grass seed and being planted searches of the scientifi c literature, internet populations at Mt. Arrowsmith and Der- by acclimatization societies (Trewick et al. resources, and discussion with Australian went Bridge that are thought to have come 2004). Eleven species are naturalized in the and international experts. from nearby road maintenance depots. United States (Rinella and Shelley 2002). Recently, concern has been expressed that Hawkweeds have also invaded Japan, Hieracium species in Australia seed and plant parts may be dispersed by Canada and Patagonia (Svavarsdottir et Four Hieracium spp. have been found mountain bike riding, which is a popu- al. 1999, Wilson and Callihan 1999). naturalized in Australia: H aurantiacum, lar recreation activity on Mt. Wellington Plant Protection Quarterly Vol.22(2) 2007 77 close to a hiking track, and seed may have been transported by a bushwalker (Rudi Pleschutschnig personal communication). Sydney Since 1999, H. aurantiacum has spread south to south-east from Falls Creek due to Canberra prevailing summer winds. Field surveys conducted in January and February 2004 showed H. aurantiacum present in Falls Creek Village and on some ski slopes to the south (Carr et al. 2004). Control efforts started around 2000, involving surveying, Melbourne mapping and spraying populations by resort management and Parks Victoria, and have been widely supported by the local community. Many populations in the Falls Creek area are believed to have been eliminated, although the species still occurs within the Alpine Resort and adjacent parts of the Alpine National Park near Rocky Valley Dam. Hieracium H. aurantiacum aurantiacum has not been found at Heathy H. murorum Spur since the 1999 record (Carr et al. H. pilosella Hobart 2004). However, isolated populations have H. praealtum been found in the Basalt Hill area (Carr et al. 2004, N. Williams and Lynise Wearne 200 kilometres personal observations). In summer 2002/2003, a population of H. aurantiacum was discovered by Figure 1. Sites of known naturalizations of Hieracium species in Australia. bushwalkers in a remote area of the Mt Buller ski resort along a narrow black ski run. Although bushwalkers were initially (Andrew Crane personal communica- January 2003 fi res. It established in an area suspected as the source of the infestation, tion). Hieracium aurantiacum now occurs up to 500 m long, and formed a monocul- it is now thought that seed was brought on roadsides, public open spaces, walking ture in some areas (David Lawrence per- to Mt Buller on ski machinery transported tracks and in private gardens (National sonal communication). Thus far there has from Falls Creek. After prompt seed-head Heritage Trust 2003). It generally shows only been a single control attempt. Dense removal and spraying with herbicide, a preference for disturbed areas but may vegetation and non-flowering plants only a few plants were found on the site also occur in open woodland (National means that some individuals were prob- of the initial infestation in 2004/2005. Heritage Trust 2003). Minor infestations ably missed (Keith McDougall personal However, two additional plants, that were may provide stepping stones for spread, communication). Eradication attempts are also subsequently destroyed, were found even when surrounding vegetation is re- continuing at these locations, including along a track leading from the ski run. sistant to establishment. monitoring and survey beyond the origi- In summer 2005/2006, surveys revealed nal infestations for further populations the original infestation had spread onto New South Wales (Keith McDougall personal communica- a batter and downslope into native In New South Wales, H. aurantiacum was tion). vegetation, predominantly E. paucifl ora sold by nurseries on the South Coast and with a reasonably dense Podolobium Southern Highlands (Burton and Dellow Victoria alpestre Crisp & P.H.Weston understorey 2005). It was fi rst recorded as naturalized Hieracium aurantiacum was fi rst recorded and scattered boulderfi eld with Podocarpus in the Toolong Range, Kosciusko National as naturalized in Victoria in January 1999. lawrencei Hook.f. (Louise Perrin personal Park in December 2003 (Burton and Del- It was found 1600 m above sea level in communication). Control efforts are low 2005, McDougall 2004). This popu- disturbed roadside and ski-fi eld vegetation, continuing. lation was found growing in Eucalyptus and E. paucifl ora heathy woodland, in the Hieracium aurantiacum has also been paucifl ora Sieber ex Spreng woodland with Falls Creek Village during a Melbourne recorded in a garden bed containing alpine a grassy understorey (McDougall 2004). University Field Botany class (Carr et al. and arid plants at the Ballarat Botanic Many plants were still present a year after 2004, Morgan 2000). It is thought to have Gardens. The size of this infestation was spraying, in December 2004 (Keith Mc- been growing as a garden plant in Falls about 15 m2 and consisted of 20–50 plants. Dougall personal communication). More Creek Village since at least 1985, from seed It was originally planted in the Gardens recently, in late 2005, a well-established deliberately introduced from Europe (Jill and ongoing eradication efforts have population of H. aurantiacum was found Dawson personal communication). reduced the population. The species has near Ogilvies Creek, 7 km to the south- At least ten populations were present also been found for sale at nurseries in west, at approximately 1450 m above sea in 1999, each of more than 500 individuals, South Gippsland and western Victoria, level. It is thought that this population was some more than 1 km from the presumed and growing in private gardens in West the source of previously discovered plants. source (Morgan 2000). The majority of Gippsland (Michael Hansford and Randall The area is a former Snowy Hydroelectric- these populations were located in, or Robinson personal communication). ity Scheme town site, and includes the re- near, Falls Creek Village (Morgan 2000) mains of plantings such as fruit trees. Hier- but one population was discovered inside Hieracium praealtum Vill. ex acium aurantiacum may have been present the Alpine National Park, at Heathy Spur, Gochnat (King devil hawkweed) here for 40 years prior to its discovery, two kilometres from the village (Carr et Hieracium praealtum can reach a height of but is thought to have spread after the al. 2004). This population was located 45 cm (Webb et al. 1988) but grows smaller 78 Plant Protection Quarterly Vol.22(2) 2007 on poor or shallow soils, or in exposed ar- Hieracium pilosella L. (mouse-ear Canada and New Zealand (NatureServe eas (Blood 2004). The majority of leaves oc- hawkweed) 2006, Webb et al. 1988). cur in a basal rosette (Webb et al. 1988). The Hieracium pilosella produces a single, pale species has yellow fl owerheads in clusters yellow fl owerhead at the top of a 2–15 New South Wales of 3–35 at the top of the stem (Webb et al. cm vertical stem. The basal rosette of dull In Australia, H. murorum was initially 1988). Flowering begins in November in green leaves is white underneath due to found at Katoomba, New South Wales New Zealand (Makepeace 1985a). Hier- dense, stellate hairs (Espie 2001, Webb et covering less than one hectare. This pop- acium praealtum is native to Europe and al. 1988). The species is native to Europe ulation consisted of approximately 1000 Asia, and occurs as a weed in New Zea- and Asia, and naturalized in New Zea- plants when it was discovered in 1998 land, Canada and the United States (Blood land, Canada, and the United States (US (Hosking et al. 2003). Another population 2004, Carr et al. 2004). Department of Agriculture 1994). Hier- was subsequently found at Mt. Irvine and acium pilosella has the greatest abundance consisted of over 100 plants growing in Victoria and widest distribution of the Hieracium lawns and a garden around a car park In December 2003, Hieracium praealtum spp. present in New Zealand (Espie 2001, (Hosking et al. 2003). This population is subsp. bauhinii (Besser) Petunn. was found Svavarsdottir et al. 1999). It occurs along now limited, with only two individuals on the edge of the Alpine National Park, the eastern seaboard and in the Great found in 2006 (Chris Graves personal adjacent to Falls Creek Resort north of Lakes and Pacifi c Northwest areas of the communication). Control of these popu- Rocky Valley Dam, at 1600 m above sea United States (NatureServe 2006). lations is ongoing. Hieracium murorum level (Blood 2004, Carr et al. 2004). The has not been recorded as naturalized in approximately 3 ha infestation of over Tasmania any other Australian states (Hosking et al. 200 000 plants was the fi rst record of H. A small population of H. pilosella L. subsp. 2003). praealtum in Australia (Blood 2004, Carr et nigrescens (Fr.) Nägeli & Peter was discov- al. 2004). The invasion-source is unknown, ered in 2001 during a routine botanical The ecology of Hieracium species but seeds may have been introduced on survey for proposed road works on the There is a lack of detailed knowledge contaminated equipment imported from Midlands Highway in southern Tasma- about the ecology of Hieracium spp. in New Zealand to construct a nearby ski lift nia. The infestation extended over 50 m2 Australia. General information sourced around 2000. Other possible vectors include in three patches along a roadside fence- predominantly from international studies bushwalkers, campers or overseas visitors line and a short distance into the adjacent and focusing on species from the Pilosella (Carr et al. 2004). The infested area consists paddock, and had a high density, vary- group is reviewed below. Consequently, of a partially rehabilitated quarry with ing from 40% to 80% cover (Rudman and ecological responses may differ under vehicle tracks and a picnic area. Control Goninon 2002). The origin and age of the Australian conditions. occurred quickly after its identifi cation infestation is unknown. Due to rapid iden- and over four kilograms of fl ower and tifi cation and notifi cation, an eradication Reproductive biology seed-heads were picked before the site program was developed and integrated Hieracium spp. show variation in reproduc- was sprayed twice with herbicide (Rudi with the road works program. It involved tive strategies, both within and between Pleschutschnig personal communication). removing the top 15 cm of soil from in- species (Morgan-Richards et al. 2004). The site has been quarantined, fested areas and a substantial buffer area, Among species in the Pilosella group, interpretation signs installed, is monitored, and burying it beneath the roadworks. plants spread vegetatively and via move- and regenerating Hieracium plants are Subsequent monitoring of the site has not ment of seed (Makepeace 1985a, Webb controlled on a regular basis (Craig Hore detected any regeneration (Rudman and et al. 1988). Vegetative spread occurs via personal communication). Further spread Goninon 2002). stolons and rhizomes. This strategy leads of the species was narrowly avoided to dense populations expanding clonally, after soil from the site contaminated with New South Wales while seeds allow medium- and long-dis- Hieracium seed was moved six kilometres Hieracium pilosella has been sold by nurs- tance dispersal. east to Langfords Gap, with the intention eries on the South Coast and Southern Most members of the Pilosella group are of using it along aqueducts in the area. Highlands of New South Wales (Burton facultative apomicts (Bicknell and Borst The contaminated soil was subsequently and Dellow 2005) suggesting that gar- 1994, Bicknell et al. 2003) meaning that quarantined and germinating Hieracium den and naturalized populations may they can produce seeds without fertiliza- plants sprayed with herbicide (Charlie be present in the region. There is also a tion (Koltunow and Grossniklaus 2003). Pascoe personal communication). specimen collected in 1992 from Nursery Facultative apomicts can take advantage During fi eld surveys in January/Febru- Swamp in Namadgi National Park in the of sexual reproduction, producing geneti- ary 2004, a satellite infestation of H. praeal- Canberra Herbarium. Recent searches of cally diverse offspring, but can also pro- tum was found growing in open heathland the area have failed to fi nd any existing duce seed asexually, allowing for long-dis- at Ruined Castle within the Falls Creek populations (Trish MacDonald personal tance dispersal in the absence of pollen Alpine Resort (Carr et al. 2004). Further communication). from conspecifi cs. satellite infestations were found in Decem- ber 2005 close to the track to Wallaces Hut, Hieracium murorum L. (wall Dispersal, establishment and approximately 2700 m from the original hawkweed) growth infestation, and on the side of the Bogong Hieracium murorum grows 20–50 cm tall, Long-distance dispersal in Hieracium is High Plains Road near Basalt Hill (Craig with the vertical stem supporting 5–15 primarily by wind dissemination of small Hore personal communication). Given bright, yellow fl owerheads. The original seeds. Stergios (1976), however, found the large source population that produced record of the species in Australia was dis- that the majority of H. aurantiacum seeds seeds for at least four years, and the super- covered fl owering in November (Hosk- were deposited within 2 m of the source fi cial similarity of H. praealtum to common ing et al. 2003). Leaves are predominantly patch. This suggests that long-distance exotic species, it seems likely that further basal and dark green in colour (Webb et wind dispersal may be a rare event for populations of H. praealtum remain unde- al. 1988). Also known as golden lungwort this species. Hieracium spp. can also be tected around Falls Creek and adjacent (Espie 2001), H. murorum is native to west- dispersed by animals, water and in mud. parts of the Bogong High Plains. ern Asia, the Caucasus and Europe (Tutin The seeds have minute barbs along their et al. 1976) and is naturalized in the USA, ribs that enable them to attach to hair, fur, Plant Protection Quarterly Vol.22(2) 2007 79 clothing and vehicles (National Heritage (Makepeace 1985b). Areas of disturbance risk of invasion (National Heritage Trust Trust 2003). Road maintenance and ski in a suitable environment are likely to be 2003) because their structure and composi- equipment have also been implicated in sites of initial invasion. These allow pro- tion pose few effective barriers to seedling dispersal of seeds and plant fragments duction of an increasing number of prop- establishment (Makepeace 1985b, Rose and (National Heritage Trust 2003). Dispersal agules that invade less favourable adja- Frampton 1999). However, Hieracium spp. modelling is one promising predictive tool cent areas (Duncan et al. 1997). Although have also been found growing in E. pau- that could be more widely applied (Wil- the likelihood of an individual Hieracium cifl ora woodlands and alpine heathlands. liams et al. 2006). plant establishing and surviving is low, the Areas of vigorously growing grass and Seeds are normally dispersed within large number of seeds produced by estab- pasture are more resistant to Hieracium es- days of maturation (Makepeace 1985a) lished plants makes fi nding new popula- tablishment, and fertilizing and oversow- and most can germinate immediately tions a management priority. For example, ing with pasture species are advocated as upon release (Johnson and Thomas 1978, H. praealtum and H. pilosella patches 10 cm2 effective control techniques in agricultural Makepeace 1985b, Stergios 1976, Tho- in area can produce up to 2700 and 1300 areas of New Zealand (Espie 2001, Rose mas and Dale 1975). However, germina- seeds per year respectively (Makepeace and Frampton 1999, Scott 1993). tion of late maturing seed is enhanced by 1985a). Consequently, identifying sites in cold treatment (Stergios 1976) suggesting the vicinity of known populations with Conclusion some seed is innately dormant (Thomas conditions suitable for Hieracium estab- Four Hieracium spp. are naturalized in Aus- and Dale 1975) and may remain viable in lishment is important. tralia. Once detected, prompt treatment the soil for up to seven years (Panebianco A number of studies in New Zealand has reduced most known populations and and Willemsen 1976). Mass germination have found that soil moisture is an impor- limited spread of these hawkweeds on of Hieracium spp. is triggered by rainfall tant predictor of Hieracium invasion. Rose mainland Australia. However, it is likely (Johnson and Thomas 1978, Makepeace et al. (1998) found that H. pilosella cover that undetected populations exist. Popula- 1985b). Seedlings have a low probabil- tended to peak on sites with intermedi- tions of H. aurantiacum in Victoria and New ity of survival and are highly sensitive to ate soil moisture. Soil moisture was the South Wales, H. praealtum in Victoria and drought stress (Johnson and Thomas 1978, only variable that signifi cantly predicted H. murorum in New South Wales were able Makepeace 1985b). presence of H. praealtum, which tended to to set seed and disperse for a number of Once established, Hieracium spp of the establish on sites with a higher moisture years prior to their detection and may have Pilosella group can rapidly increase the index (Svavarsdottir et al. 1999). This fi nd- established in areas surrounding known area they occupy via rhizomes and stolons ing was repeated by Duncan et al. (1997), populations. In addition, Hieracium spp. (Espie 2001, Rinella and Shely 2002). How- who, after taking into account elevation, were sold by nurseries in at least two states ever, spread by this means is infl uenced by found that the cover of Hieracium species providing additional but unknown sourc- biotic barriers present in the invaded com- was lower at more xeric sites and on soils es of infestation. Systematic searches in the munity, such as competition from estab- with lower moisture holding capacity. vicinity of known Hieracium infestations, lished plants (Rose and Frampton 1999). Although not essential for Hieracium that are informed by the species biology, Plants generally send out between three invasion (Johnstone et al. 1999), evidence ecology and invasion history at other sites, and eight stolons early in the growing suggests that Hieracium spp. are more will help to prevent their spread in Aus- season, while at the same time producing likely to establish in areas that have been tralia. International liaison and co-ordinat- infl orescences (Makepeace 1985a, Stergios disturbed (Rose et al. 1998, Treskonova ed programs including control, monitoring 1976, Wilson and Callihan 1999). Daugh- 1991). Experiments have found that soil and education will also be important. ter plants form at stolon tips (Makepeace disturbance is essential for establishment 1985a, Thomas and Dale 1974) but can also of H. pilosella (Jesson et al. 2000) and that Acknowledgments form from adventitious root buds in some H. praealtum germinates most readily on This paper is a product of research funded species (Wilson et al. 1999). Vigorous sto- bare soil (Johnson et al. 1978, Makepeace by the Parks Victoria Research Partners Pro- lon growth can quickly expand colonies 1985b). Sites colonized by H. pilosella in gram and The Baker Foundation. We would forming dense mats of up to 3800 plants eastern Otago, New Zealand tended to be like to thank Parks Victoria staff John Wright, per square metre (Thomas and Dale 1974, degraded, with a higher percent cover of Brooke Ryan, Craig Hore, Rudi Pleschut- Wilson and Callihan 1999). The vegetation bare ground and a lower cover of grass schnig and Charlie Pascoe for their support dynamics of Hieracium colonies has been tussocks (Johnstone et al. 1999). Rabbit ac- and for providing information on Victorian studied in New Zealand, USA and Canada. tivity was a signifi cant predictor of Hier- Hieracium populations. Trish MacDonald, Plants on the periphery of colonies produce acium cover in Canterbury (Duncan et al. David Lawrence, Andrew Crane, Michael more stolons, fl owerheads and seeds than 1997). Pastoral disturbances, such as burn- Hansford, Stan Cantwell, Louise Perrin, Jill those in the interior which can die off in ing and grazing, are also thought to have Dawson, Keith MacDougall, Chris Graves dry conditions (Makepeace 1985a, Stergios increased vulnerability of New Zealand and David Lewis also provided valuable 1976, Thomas and Dale 1974, 1975). This tussock grasslands to Hieracium invasion information on Hieracium populations in suggests that density-dependent process- (Rose and Frampton 1999). their jurisdictions. John Morgan and Char- es are important in regulating hawkweed In Europe, hawkweeds are found in lie Pascoe provided valuable comments on populations (Wilson and Callihan 1999). pastures, mountain meadows and dis- drafts of this paper. Amy Hahs assisted in turbed areas (Wilson and Callihan 1999). the production of Figure 1. 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