156 Protection Ouarterly Vol . 3(4) 1988

The Biology of Australian Aleutian Islands and montane Central America.ltisacommon in Argentina, 18. Hypochoeris radicata L. Columbia, Chile and South Africa (Aarssen 1981). It is the most widely distributed introduced weed in New Zealand on both an altitudinal and geographi c basis (Healy 1976). In Australia N. radicala is found generally throughout the temperaLe zone, from sea level to the upper levels of vegetation at about 2000 m (Burbidge and Gray, 1970). Il is found in all States (Figure I) but is most widespread in Tasmania, Victoria and New South Wales.

Lesley Cameron History Depa rtm ent of Geography, Unive rsity of New England, Armidale, New South Wales 2351 Curren t address : Roseworthy Agricultural College, Roseworthy, South Australia 5371 Illtroduction The date and place of introduction of H. radicala lo Australia is uncertain and iLS subsequent spread a maller of some Name from a hard, over-wintering base. Leaves: conjecture. It is likely that it originally The taxon Nypochoeris L. (family in a basal roselle, hairy, sinuate to entered south-eastern Australia asa bal last ) is a cosmopoli Lan of pinnatifid, usual ly scabrous,2-20cm long plant (Kloot, pers. comm.) in the same about 100 species, none of which is and 0.5-7 cm wide. Stems: leallessscapes, way as it was introduced to indigenous to Australia. Thrcc species are often several per plant, broader below the (perkins 1883). It appears lo have been an naturalized in Australia,all as introductions hcads, scaly, sparsely and minutely early arrival, well established by the time from , Asia or NOM Africa (Beadle bracteate, possessing a milky juice. serious boLanical exploration began. The 197 1). The generic name may be spelled : yeliowcapiLUla, 20-40 mm wide, earliest plantlisLS and regional n oras des­ lIypochaeris (Hitchcock el al. 1955; usually several. FloreLS: ligulale, numerous, cribe H. radicata, including Bentham 's Clapham el al. 1962, 1981) or , more the outer longer than the involucre and ' Flora Australiense' of 1866, though it is commonl y, NypocilOeris (Index Kewensis; four times as long as wide, golden-yellow not me ntioned in Brown's lis t of Flora Europaea). The common name for but grccni sh on back. Involucre: IQ-15 1802- 1804. lIypochoeris radicala L. is caLSear, mm high m anthesis, up to 25 mm in , Il has been suggested that species of natwccd or fal se dandelion, the latter bracLS im bricale, glabrous or hi spid. Fruit: lIypochoeris, including N . radicala, were indicating iLS close resemblance to an achene, brown, striate, scabrid above deliberately introduced into the western TarlJXl1cum officinale, a species with which and allenuate with long or short smooth and northern plains of Victoria in the I 840s it is ofle n confused. Il may also be called beak, plumose with two rows of in order to rcplaccM icroseris scapigera. a long-rooted calSCar to distinguish it from hairs commonly barbellate. staple food plant of Aborigines which has II. glabra (Maiden 1920). been vinually eradicated by domestic In the rosetle stage, H. radicata is CYlology di stinguished from capil/aris (hawksbcard), Leonlodon allll4mnalis A chromosome number of2n = 8 has been (autumn hawkbit) and TaraxaCllm spp. obtained for Canadian and British material , , (dandeli on) by the presence of hairs on the (Mulligan 1976; Parker 1975; Aarssen \ leaf margins, from II. glabra (smooth 1981). Rare tri somics wi th 2n = 9 have catsear) by the thicker, rough- hai ry leaf been reponed for Indian material Panigrahi surface, from Leonlodon taraxacoides by and Kammathy 196 1). A detailed the simple leaf hai rs, and from Crepis cYlO logical sLUd y is given by Dvorak and laraxacifolia (beaked hawksbeard) by the Dadakova (1977). rounded leaf lobes. The branched nower stalks distinguish it from dandelion and Distribution hawkbil, theabsenccofleaveson ~le nower stalk from all species of Crepis, and the II. radicala is acosmopoliLan species wi th larger nower head and lack of dimorphic a wide global distribution, occurring over fr uits from the relmed II. glabra; stem a broad latitudinal and altitudinal rdnge. It galls di stinguish the species from all others is native lo most of Europe, being recorded in the dandelion group except II. glabra at 62°47'N. in Scandinavia and to 1400 m (Healy 1944). in the Alps, much of northern Asia and pans of Nonh Africa (Burbidge and Gray Description and account of 1970; Beadle el al. 1972; Turkington and variation Aarssen 1983). Il is widely establi shed Ilypochoeris radicata is a hairy, perennial over ~1C eastern half of Nonh America, the thm grows to a height of 5- 70 em Pacific Northwest, Hawaii , Alaska, the A single plant of Hypochoeris radicata Plant Protection Ouarterly Vol. 3(4) 1988 157

The major factors limiting its distribution are nOl known, though are thought to be, in Europe, winter cold at its northern and eastern limits and summer heat at its southern edge (Turkington and Aarssen 1983). In Australia it is possible that moisture availability isof equal importance to temperature in determining distribution on local and conti nental scales. I n arid and semi-arid central Australia the species is recorded only in the Alice Springs region and th ere only in disturbed urban environments. In partsofWestern Australia where the species is found - mai nly in the southern half - it is generally much less common than N. glabra (R. J. Hobbs, pers. comm.).

Substralum

H. radicala tolerates a wide range of soil type, texture and pH. It has been recorded on light sands and gravels (Muenscher 1949) and on clays (Saxby 1943)andfrom soils with pH values ranging from 3.9 to 8.6 (Turkington and Aarssen 1983). It is Figure 1 Occurrence of Hypochoeris radicala in Australia nOl, however, ubiquitous. It is absent from liveslOCk (Gott 1983). N. radicala docs Bailey (1909) for Queensland and both sites subject to prolonged waterlogging have a small, edible taproot,though much Whittet (1968) and Lamp and Collet (although it may be found on swamp smaller and less palatable than that of M. (1976) for Australian weeds generally. margins) and is absent from or rare on scapigera .1t is difficulttoassess the extent The species, however, has never app­ highly calcareous soils. World-wide, the to which these deliberate introductions eared on any li st of proscribed weeds in species is associated with well-drained extended the range of the species, which Australia, although those proclaimed in soils (Ho 1964) which may be generally was already present in other parts of the Commonwealth of Australia Gazette moist (Salisbury 1964) or show marked Victoria at that time. of December 1912 included N. glabra. In annual fluctuation s in moisture content describing N. radicala , Maiden (1917) (Rumball 1978). In New Zealand N. radicala often coloni7.es dry microsites in Stalus considered that 'its characters and defects are similar' to N. glabra. The species is mesotrophic mire vegetation (Healy 1962). Despite its global distribution and its perhaps best considered as a weed of In South Australia it may be found on tidal widespread and abundant occurrence relatively minor importance in agricultural salt marshes but only in sites with a throughout Australia, there has been little terms (Clemson 1985) but with some considerably lower soluble salt content research on N. radicala. Maiden (1920) potential for spread given its capabilities than the surrounds and which are rarely, if emphasized this problem, pointingoullhat proven in Britain and Canada (see later) ever, flooded by tides (Specht 1972). It 'It is one oflhose with which we are and its behaviour in natural plant tolerates relatively nutrient-deficient soils so familiar and which has no outstanding communities in Australia. such as Australian soils which are deficient characteristics, that little has been written in phosphorus (Leigh and Mulham 1965). aboutil' (Maiden 1920,p.124). As a result, Habitat the extent to wh ich the species is a problem CommuniJies plant in Austral.ia is hard to determine. Climatic requirements Almost all regional floras describe N. The species is adapted to a wide range of In Australia N. radicala is most often radicala as a weed: Curtis (1963) for climaticconditions(Aarssen 1981). While found in pastures (irrigated and dryland), Tasmania, Specht (1972) for South its geographical distribution mightsuggest cultivated fields, lawns (Leigh and Mulham Australia, Willis (1972) for Victoria, that climatic limitations arefew, its major 1965; Whittet 1968), fallow paddocks Burbidge and Gray (1970) for the areas of occurrence are in cooJer,temperate (Cunningham el al. 1981), roadsides and Australian Capital Territory, Costin el al. locati ons. The plant is deep-rooted and waste places (Curtis 1963), disturbed sites (1979) for the Kosciusko region, Beadle apparently drought-resistant In temperate and reclamation areas (Costin el al. 1979) el al. (1972) for the Sydney region, Australia it is found in drier parts, moister and in natural plant communities at aU Cunningh3J11 elal. (1981) for western New sites tending to be populated instead by elevations (Burbidge and Gray 1970). South Wales, Beadle (1980) for northern Taraxac um officinale, but is generally Other studies repon its occurrence on New South Wales, andJessopelal. (1981) absent from the arid zone. In South grassy dunes in the U.K. (Clapham el al . for central Australia. N. radicala is al so Australia, N. radicala is recorded as 1962) and in Callunelurn communities considered in most texts and manuals widespread in disturbed eucalypt forests (Miles 1974), in peat bog in Ireland (Ridley specifically on weeds: Black (n.d.) for in a Mediterranean climate, but is not 1930) and in modified tussock grassland South Australia, Ewart ( 1972) for Victoria, found in the driest areas (Specht 1972). in New Zealand (Healy 1962). 158 Plan! Pro!8Ctlon C>.Jarterly Vol . 3(4) 1988

Doing (1972) made an exhaustive herbicidal sprays (Ormrod and Renney arid Australia, the seasonal behaviour is phytosociological analysis of the pasture 1968; Aarssen 198 1). apparently reversed,the plant fl owering in and weed communities on the hills and winter and persisting as a basal rosette in tablelands in the Australian Capital Perennation summer (Cunningham el al. 1964). No Territory and nearby areas. H. radiCala is detailed study exists of the phenological listed underhisGroup 18 which is described Under favourable conditions, H. radicata development of H. radicata in Australia. as 'species of grasslands or weed frequently overwinters as an above-ground, communities, with preference for moist evergreen rosette. This occurs in areas Physiological data soils. . . . invading where the average winter temperatures are native pastures on a large scale during a above freezing, as in British Columbia and There has been very lillie research on the relatively early stage of improvement'. in temperate Australia. It can, however, effects of light, water regime, mineral Two studies in Victoria, one of respond to the onset of very cold weather nutrient supply or temperature on the agricultural and one of natural as a true hemicryptophyte, through the growth of H. radicala , or on its rate of communities, revealed a number of plant dieback of above-ground parts, leaving photosynthesis and transpiration. Almost species commonly associated with H. perennating buds at ground level no physiological studies on the species radicata. In a study of the vegetation of (Turkington and Aarssen 1983). Under appear to have been done with Australian roadsides and adjacent farmland on the conditions of very high average material, the most substantial physiological Mornington Peninsula, Lane (1976) found temperatures, fl. radicata acts as a studies being on Dutch populations. H. radicata to be one of the few alien therophyte in western New South Wales Lambers (1979) and van de Dijk (1980 species of the roadside communities which and other semi -arid areas of Australia, a.b) conducted comparative physiological was also common in pastures (Lane 1976). genninating and flowering in the cooler studi es on the uptake and assimilation of Similarly, ina study of the spread of weeds winter months and dying after fl owering nitrogen by two subspeciesof Hypochoeris from roadsides into native sclerophyll (Cunningham et a1 . 198 1). Vegetative radicata , H. radicata ssp. radicala and fl. forest in northern Victoria, H. radicata propagation of H. radicala occurs only by radicala ssp. ericetorum. These subspecies was found to be the most abundant alien perennating buds(TurkingLon and Aarssen show slightly different distribution pallems species in each of the three eucalypt 1981). in the field, ssp. radicala being absent communities studied (Amor and Stevens Panigrahiand Kammathy (1961)contend from strongly acidic soils and ssp. erice/orum from nUlrient-rich soils 1976). Most of the roadside associates of thallhe propagation of the species is largely H. radicata did not invade either the by vegetative means, the plant splitting up (Lambers 1979). The shoot/ ratio of pasture or eucalypt communities. at ground level and producing clones. ssp. ericetorum showed little response to These studies attribute the differences Specimens from coastal Argentina increasing nitrat.e concentrations. whereas between plant communities in composition (Crovetto 1944, cited in Aarssen 1981) ssp. radicala showed a strong response. and frequency of alien species to either and BritishColumbia (Aarssen 1981) were This, coupled with a sharper decline in different types and levels of disturbance demonstrated as developing 'axillary growth rate of ssp. ericetorum I month (Lane 1976) or to different levels of light vegetative proliferation ', in which roselles after sowing. could explai n the absence of intensity (Amor and Stevens 1976). The of leaves similar to the basal rosette had ssp. ericelorum from nuLrient-rich soits studies conclude that high levels of both fonned in the ax ils of the stalks. (van de Dijk 1980a). When grown with di sturbance and light intensity are These axillary rosettes were able to initiate ammonium as the only source of nitrogen, necessary for the establishment of alien advemitious roolS and survive when ssp. radicala had an only slightly hi gher plants. While this may be valid in general, artifiCially severed from the floral stalks yield than ssp. ericetorum, the difference it may not neeessarily apply to all species and placed in moist sand (Aarssen 198 1). being greater at pH 4.5 than at pH 6. Van or all communities. H. radicala has been Undcr favourable conditions, flowering de Dijk (1980b) concluded that both recorded from apparently undisturbed plants can be produced from in 2 subspecies had similar ammonium­ sclerophyll communities and from a months (Ho 1964). This rapid development, nitrogen requirements and thallheabsence rainforest where light intensi ty is very low in conjunction with its clonal spread, of ssp. radicala fro m strongly acidic soils (Cameron, unpublished data). contributes to the persistence of the plant could not be explained by the low pH. as a weed in tUlf (Ho 1964). Australian material from the Northern Tablelands of New South Wales was used Growth and development Phenology in a mineral deficiency trial, testing the dry Morphology weight response of above-ground parts of fl. radicala often overwinters as an above­ H. radicala totheomission from the growth H. radicata has a prostrate rosette growth ground rosette, although in parts of medium of a range of essential mineral habit, with the leaves often very closely Australia this phenological stage may occur elements (Cameron, unpublished data). In appressed to the ground surface, and buds over the hot summer months. Ho (1964) these trials, calci um was found to be the close to the ground. Both characteristics noted th at in British Columbia vegetative most critical growth element for H. partly protect the plant from mowing and growth occurred throughout the spring radicala. a deficiency of which resulted in grazing (Fogg 1945; Aarssen 1981). Its months; flowering was maximal in spring seedling death within 4 weeks. This, in perennial rooi system extends below the and autumn but continued sporadically conjunction with the plant's absence from root depth of many neighbouring throughout the summer; seed production highly calcareous soil s (Turkington and herbaceous species, and this may account continued from late spring toearlyautumn. Aarssen 1983) suggests that H. radicala for its high content of minerals and trace This contrasts slightly with th e may have a narrow range of tolerance for elements (Struik 1967). The leaves have phenological development of the plant in . Lack of had asimilar but less small epidermal cells and large Australia where, at least in thecoolerparts, extreme effect in retarding seedling growth. mu lticellular hairs (trichomes) which may flowering occurs mostly in the summer Other essential minertt1 elements were mfluence the retention or penetration of and seed production in autumn. In semi- found to be magnesium and phosphorus. Plant Protection OJarterly Vol . 3(4) 1988 159

H. radicala seedlings showed a positive wilh an upper limit of 136 being recorded germ ination immediately afler harvesting, response to deprivation of sulfur and (Salisbury 1964). The number of capitula decreasing to 58% after I monlh of dry micronutricnts, and some response to on each individual plantdiffers,particularly storage at room lemperature and after 2 deprivation of nitrogen. Seedlings grown with time of year, but generally varies months decreasing markedly to 4%. In contrast, Cameron (unpubJisheddata) using wilhout micronutrients actually exhibited from 2to II (Ho 1964),mleastforCanadian material. The average weight (air dried) of achenes harvested from populations of H. more vigorous growlh Ihan those grown in radicata on Ihe Northern Tablelands of complele nutrients, and Ihose wilhout sul­ an achene, including Ihe pappus, is 0.6- 0.8 mg (Turkington and Aarssen 1983). New Soulh Wales, found under similar fur only slighUy less Ihan Ihe complete. storageconditions, lhatgermination varied This response could account for Ihe A feathery pappus aids di spersal by - for relatively short distances by natural from 62% to almost 100% for freshly abundance of H. radicala in parts of harvested achenes, decreasing to 60% after temperate Australia where Ihe soils are means. However, human agencies may carry Ihe pappus long di stances. The very I monlh of storage and to 34% after 2 deficient in sui fur or in trace elements. The open form oflhe pappus gives Ihe propagule months. Even afler 12 monlhs' storage at res ults for Ihe dry weights were confirmed a high lerminal velocity of 40.5 cm s" room temperature, lhe achenes achieved a by Ihe response of Ihe under the same (Sheldon and Burrows 1973). Sheldon and germination level of 19%. treatments. Roots of plants grow ing wilhout Burrows (1973) found maximum dispersal micronutrienLS, suLfur and nitrogen grew distances of a fmitto be 0.67, 1.33 and Hybrids much longer and more densely Ihan those 2.00matwindspecdsof5.7, 10.9 and 16.4 Hybridization occurs readily between H. of plants grown wilh a complete treatment. km h" respectively. On Ihe ground Ihe These data again indicale a physiological radicala (2n = 8) and H. glabra (2 n = 10), achene lies on its side, supported by the producing an F, with 2n = 9 (Turkington basis for Ihe distribution of Ihe species hairs of Ihe pappus, from which position it and Aarssen 1983). Hybrids probably occur throughout Australia and particularly its may be carried further by wind gusts occasionally where Ihe parents grow presence in unimproved pastures and (Turkington and Aarssen 1963). The togelher. in Britain Ihey have been rccorded nillgelands. achene may beeome attached to Ihe occasionally in parts of Wales and soulhern On a dry weight basis, approximale values substratum by Ihe short processes on its England and are also known from of chemical constituents for II. radicala su rface. Attachment in this fashion to the Germany, Switzerland and Sweden. No plants in New Zealand tussock grasslands fcct and plumage of birds has been hybrids have been recorded in Australia areprotein 10-15 %, fibre 10-29%,caIcium observed, as has transportation by (Everist, pers. comm .), Ihough Ihey 10-20 mg g-', phosphorus 1.5-5 mg-' and (Aarssen 198 1). This latter phenomenon possibly exist where bolh species co-exist. copper 5-10 g g" (Grace and Scott 1974). has been studied on Ihe Norlhern Table­ Hybrids arc short-lived and have lands of New South Wales (Cameron, characleristics of leaf and infloreseence Floral biology unpublished data). Achenes of H. radicala intermediate betwccn Ihose of the two placed on Ihe ground in eucalypt woodlands parent species. The leaves of Ihe According to most sources, H. radicala were found to germinale wilhin a 2 m are usually haisierlhan in H. glabra though is cross-pollinated and self-incompatible radius of Iheir original location. A the degree of hairiness depends on Ihe H. (Fryxell 1957; Parker 1975). The stylar significant number of Ihe achenes were radicala parent. The capitula are branches are I mm long and not su fficiently not retrieved as seedlings and may have intermediate in size between Ihose of Ihe recurved to permit automatic self­ been eilher destroyed or transported two parents (Turkington and Aarssen (Turkington and Aarssen 1983). considerably furlher lhan 2 m. On a broader 1983). A1lhough fertility of F, hybrids is It has been suggested Ih at self-pollination scale, achenes can be dispersed over long reduced to about I %, viable backcrosses may be possible by Ihree means: activity distances, e.g. as contaminants of to H. radicata as parent have been of of Ihe genus in side Ihe commercial grass (Johnston 1962; produced experimentally and occur in flower head, Ihe opening and closing of Wellington 1969). H. radicata seedlings natural populations (Aarssen 1981 ). Ihe flower head, and Ihe trapping of rain were amongst Ihose germinated from Backcrosses wilh 2n = 8 arc full y infertile water inside Ihe open head (Hagerup 1954; sludge collecled from a car wash in wilh H. radicala (parker 1975). Aarssen 1981). Kerner and Oliver (1985) Canberra by Wace (1977) in a study oflhe speci ficall y list /-Iypochoeris as an role of motor vehicles in plant dispersal. Population dynamics autogamous genus. Autogamy (self­ H. radicala competes well wilh olher fertilization) occurs by elongation of the Germillation, grassland species. It has been known to ligulale corolla and consequent uplifting The achenes of H. radicala are immed­ displacc every olher plant in pastures in oflhe adherent pollen, a pollination device Britain including while clover (Trifolium apparenUy common in plants whose iately germinable, exhibiting no dormancy period prior to germination (Ho 1964). repens) and in less than 3 years to destroy capitula have peripheral ligulate florets good pastures (Ridley 1930). Although Prematurely harvested achenes are longer !han Ihecentral ones. The pollination such extensive colonization does not appear nonviable (Gill 1939). Light is required mechanism is detailed in Kernerand Oliver to have occurred in Australia, H. radicata for germination (Ho 1964; Wesson and (1895, p.375). The average daily pollen isa common weed of grasslands and lawns yield is 60 mg for 100 plants for British Wareing, 1967; Aarssen, 1981). and is a troublesome weed of irrigated malerial (percival 1950). The pollen is Germination patterns vary across Ihe pastures on Ihe Riverine Plain (Leigh and 74% viable and there is no plant's distribution, presumably in Mulham 1965). In Australia Ihe species is (panigrahi and Kammathy 196 1). response to some climatic pararnelers. In a successful colonizer of sclerophyll British Columbia thereare two germination folCSts, spreading from roadsides (Amor peaks, in spring and autumn (Ho 1964), Seed production and dispersal and Stevens 1976). This contrasts with Ihe whereas in soulh-easlern Australia most situation in Britain where it is almost totally The di spersal unilof II. radicala is an germination occurs in autumn (Leigh and absent from intact woodland. achene wilh pappus. Each plant produces Mulham 1965). In laboratory experimen ts H. radicala may have allelopathic effects an average of 44 achenes per capitulum , in Canada, Ho (1964) found 68% on olher species (Aarssen 1981). LeachaleS 160 Plant Protection Ouanerly Vol . 3(4) 1988 from pots of H. radicata reduced the dry Vses Response to other human weight of shoots of several grassland manipUlations species (Newman and Rovira 1975). The H. radicata is eaten readily by slOCk while species appears 10 be autolOxic, i.e. it is green and may provide a considerable H. radicala exhibits various responses in inhibited more by exudate from its own portion of forage intake in some situations terms of morphology and population species than from other species (Newman (Cunningham et aJ. 1981). In Australia dynamics when either the plant itself is and Rovira 1975). This characteristic has and New Zealand it is one of the most treated in some way or the community in been used to explain an apparent palatable species occurring in tussock which it is growing is subjected to some phenomenon of the species being usually grasslands and is more productive than form of manipulation. The growth found as isolated individuals or small otherherbs(CoopelaJ.1953;Healy 1962), responses of H. radicata under four groups of individuals and not as pure stands especially in winter (Leigh and Mulham defoliation intensities were studied by (Aarssen 1981). However, in Australia 1966). II often invades overgrazed, under­ Struik (1967). The treatments were mowed Maiden (l917)complained thatH. radicala fertilized pastures and serves 10 offset the lawn, heavily grazed pasture, lightly grazed often formed patches 'to the exclusion of decline in carrying capacity (SeweU 1950; pasture and uncUl lawn. Grazing (both most other vegetation' (Maiden 1917, Lamp and Collet 1976). Sheep will eat H. light and heavy) favoured optimal sexual p.124). The variability of this aspect of the radicata preferentially, often before any reproduction, and heavy grazing also population dynamics of thespecies requires other grass or herb (Slruik 1976). It is produced maximum vegetative weight. clarification. superior to many grasses in nutritive value Undisturbed plants produced far fewer and is comparable 10 white clover, being flowers and than plants that were high in , low in fibre, exceptionaUy grazed and also had significantly fewer Importance high in calcium and relatively high in leaves (Slruik 1967). This response 10 Detrimental copper content (Coop el aJ. 1953). II has grazing pressure helps explain the ready been suggested in Canada thatH. radicata ability of 11. radicala to colonize pastures. H. radicata possesses many typically be sown in grazed grasslands along with a It also suggests either that defoliation weedy auributes: prolific reproduction, non-aggressi ve grass (S tapledon 1948) but stimulates the formation of new leaves, or rapid spread and a large, deep root system thi s possibility apparently has not been that the presence of old lcaves suppresses making it persistent II can bea lIoublesome recognized in Australia. growth of new leaves (Aarssen 1981). weed in lawns, golf courses, ploughed The species has importance, too, in natural Leaf angles were more upright in the uncut fields and along roadsides. Its impact in food chains (Radwan and CarnpbellI968). lawn than in the other lIeatments. In mowed Australian agriculture has not been Wild pigs can cat the fleshy roots and, in lawns the leaves typically grow very close dramatic but the plant readily colonizes Canada, snowshoe hares prefer 11. radicata to the ground (Gilkey 1957). ploughed fields, untended paddocks, over other natural vegetation and even In a fi eld trial on the Northern Tablelands irrigated pastures and unimproved past­ over commercial pelleted food (Aarssen of New South Wales (Cameron, ures. In Australia, H. radicala has been 1981). unpublished data), plots in sclerophyll suspected of causing stringhalt in horses, In Australia, H. radicala has apicultural woodland whose herbaceous layer was an inVOluntary flexing of one or both hind value. Although not a major or reliable dominated by snow grass (Poa sieberana) legs brought about by ennervated tendons source of ,the plant stimulateS brood­ were subjected to a number of lIeatments (Hurst 1942). There is no scientific rearing in by providing some simulating natural disturbances-digging, evidence 10 support this contention (Leigh andanabundantsupplyofpoUen(Clemson clipping, uprooting, application of and Mulham 1965), although cases have 1985). Honey produced from the plant is herbicide and application of fertilizer. The been reported from parts of the coast, yellowish in colour, with a characteristic treated plots were then sown with seeds of tablelands and slopes of New South Wales, bitter (Clemson 1985). H. radicala and two other species, namely despite the failure of feeding tests and perennial rye grass (Lolium perenne) and grazing lIials to produce any stringhalt Control measures white clover (Trifolium repens), both symptoms (Whittet 1968). The plant is, important pasture plants, either singly or nevertheless, suspected of being In 1917, Maiden stated that 11. radicala in combination. Although overall unwholesome as fodder (Salisbury 1964) could be controlled only by means of 'a germination rates were much lower in the both in Auslralia and Britain, though it has hoe or other cutting implement'. This field than in the glasshouse, H. radicala some atlraction for grazing animals (see method of coniiol remains effective and consistently out-performed the other two below). The rosettes of H. radicala often disc harrows and rotary hoes are used on species under all trea!'11ents. The poorest harbour slugs which may be injurious to arable land. Effective control in badly response was in plots treated with fertilizer, other plants (Healy 1962). infested areas is achieved by ploughing where there was no significant difference Outside the agricultural arena, H. radic­ and cultivating for a year ortwo before re­ in germ inalion and establ ishment between ala assumes importance in AustraJia as a seeding (Aarssen 1981). In other areas fertilized and non-fertilized plots. These weed of native plant communities. II is a where the plant is troublesome, as in results do nol, however, support the very successful colonizer of sclerophyll pastures, turf and irrigated pastures, it is contention that H. radicata is suppressed forests, often spreading from roadsides readily controlled by the application of by the appl ication oforganic and inorganic and other disturbed areas (Am or and herbicides, although H. radicata is fertilizers (Turlcington and Aarssen 1983) Stevens 1976) bUl also occurring in moderately resistant 10 a number of as the plants surviving under fertilization undisturbed native plant communities herbicides such as alrazine, dalapon, were much larger and grew more (Cameron, unpublished data). Thus, whilst paraquat, asularn and picloram (Canada vigorously than those not treated with H. radicala may be considered 'of minor Weed Comminee 1967). Spraying with fertilizer. H. radicala established best importance' as a weed in the agricultural 0.1% 2.4-D is effective, although several where the community into which it was sense (Clemson 1985), its presence does treatments may be necessary to coniiol the introduced had been disturbed by digging. have conservational significance. weed (Whittet 1968). II also established well where herbicide Plant Protection Quarterly Vol. 3(4) 1988 161

had been applied prior to sowing and fairly Brunt, A. A., and Stace-Smith, R. (1978). Gott, B. (1983). Mumong - Microseris well where the resident vegetation had Some hosts, properties and possible scapigera: a study of a staple food of been uprooted, thereby contradicting the affinities of a labile virus from Victorian Aborigines. Australian claim that pigs exert some control on the Hypachoeris radicata (Compositae). Aboriginal Studies 2, 2-18. plant by uprooting it (Georgia 1914). Not Annals ojApplied Biology90, 205-14. Grace, N. D., and Scott, D. (1974). Diet only can plants tolerate this treatment Burbidge, N.T., and Gray, M. (1970). and mineral nutrition of sheep on (Guthrie-Smith 1969), but the uprooting 'Flora of the Australian Capital undeveloped tussock grassland. I. The process itself can create sites favourable Territory.' (A.N.U. Press: Canberra.) macro- and micro-element of blood fOrlheestablishmentof H. radicata. Seeds Canada WeedCommittee(l967). 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