Blackberry profile - Weeds Australia

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Blackberry profile - Weeds Australia

1.1 Blackberry inAustraliaBlackberry, a plant belonging to the Rubus genus,is considered a significant weed in Australiabecause of the extent of its negative impacts.First introduced to Australia in the 1830s, Rubusspecies originating in Europe, North Americaand Asia have now become naturalised andinfest over 8.8 million hectares of land fromsouth‐eastern Queensland to southern Tasmaniaand across to south-western Australia.The Rubus genus comprises many differentspecies of blackberry, including 10 that arenative to Australia (which require protection),as well as raspberry species and cultivars suchas dewberry (R. roribaccus) and loganberry(R. loganobaccus). The word ‘blackberry’ is oftenapplied indiscriminately to refer to any of thevariety of species.Information in this manual relates to all knownweedy Rubus species in Australia, particularlythose from the Rubus fruticosus aggregate(R. fruticosus agg.), which have been recognisedas Weeds of National Significance (WoNS) (seeFigure 1.1).The R. fruticosus agg. consists of hundreds ofdifferent named species in Europe. At least 16 ofthese species have been introduced into Australia(see Table 2.1, p. 20).History in AustraliaSpecies in the R. fruticosus agg. are among themost devastating weeds in southern Australiabecause of their invasiveness and their impact onproductive land and natural ecosystems.The R. fruticosus aggregateSpecies from the R. fruticosus agg. were firstbrought to Australia by early settlers to includein gardens and hedgerows. An article in theBathurst Free Press in 1851 reported thatblackberry was planted in the Bathurst area inthe 1830s. An article in the Sydney MorningHerald in 1851 also recorded blackberry growingin a Sydney garden.Blackberry was grown to provide fruit for jamsand pies. Records from a blackberry-pickingenterprise in Bulli, New South Wales (NSW),document that four tonnes of fruit was sent toSydney for manufacture into jams in 1894. By1912, the amount of fruit sent had grown to200 tonnes.In 1851, the Government Botanist in Victoria,Baron von Mueller, and the first Curator of theGardens at Melbourne University, AlexanderElliot, recommended that blackberry be plantedto control soil erosion along creek banks.Nine species of blackberry were planted inMelbourne’s Botanic Gardens.European origin – referred to as R. fruticosus agg. Speciesin this aggregate have been recognised as a Weed of NationalSignificance in Australia (see Table 2.1, p. 20).Rubus speciespresent inAustraliaOther introduced weedy Rubus species that havenaturalised in Australia (mainly of North American and Asianorigin). These include species that have been cultivated inAustralia (e.g. raspberry, loganberry and keriberry)(see Table 2.2, p. 21).Native Rubus species (e.g. R. parvifolius and R. moorei)(see Table 2.3, p. 21).Figure 1.1: Overview of the genus Rubus in Australia.10


In spite of the plant’s recognised benefits, itspotential weediness and associated problemswere also quickly recognised. An article in theSydney Mail in 1887 noted that ‘blackberryplanted for hedges was ruining farm land’. In1906, landowners in the Armidale ProtectionBoard area in NSW were encouraged to burnblackberry plants, as they harboured rabbits.Blackberry was declared noxious in parts ofVictoria in 1894 and in the whole State in 1908.See Appendix 1 for details of current noxiousweed legislation concerning blackberry in allAustralian States.Other weedy Rubus speciesThe North American blackberry (e.g. R. laudatus)and keriberry (e.g. R. rugosus) species havespread from cultivated plants. These specieshave now become naturalised in Australia.Problems, benefits and costs ofblackberryProblemsBlackberry can infest a large area quickly.It grows vigorously; is prickly and able topropagate vegetatively from cane tips; effectivelyspreads seed through fruit-eating birds andmammals; and is relatively unpalatable to mostlivestock. The plant can also quickly smotherother vegetation under a dense canopy. Onceestablished, blackberry causes major problems,as listed below.Reduced productivity of primary industries.Blackberry reduces the productivity of manyprimary industries, including grazing, croppingand forestry enterprises. Dense blackberrythickets shade out pastures and crops andcompete for soil moisture and nutrients,effectively suppressing productive vegetationand reducing the stocking capacity of infestedpastures.In plantation forestry, blackberry can prevent theregeneration of natural hardwood forests andreduce the capacity of softwood and hardwoodseedlings to establish and grow. The plant canalso hinder forest operations, particularly insituations where infestations are heavy andwalking access is required.Penny Richards (DPI, Victoria)Penny Richards (DPI, Victoria)Blackberry can dominate other vegetation.Blackberry can affect the establishment of forestry seedlings.11


Within blackberry’s range, many areas thatare currently free of the weed are underthreat. Blackberry readily invades new areas,establishing itself on disturbed sites suchas along access tracks, on freshly harvestedforest lands, and in areas affected by firesand floods.1.2 DescriptionProjected climatic suitability for theR. fruticosus agg. in 2030 (1 o C increase inthe global average surface temperature)Physical characteristicsPhysical features vary between the three groupsof Rubus species in Australia (see Figure 1.1,p. 10). Those within the R. fruticosus agg. aresimilar in appearance and difficult to distinguish.Their key features are outlined below. However,the other introduced and native Rubus speciesvary in many details, including leaf shape, flowerand fruit colour. Part 2 (p. 20) provides moredetailed taxonomic information to help identifyindividual Rubus species.Rubus fruticosus agg. species are perennial,semi-deciduous, scrambling shrubs.The tangled prickly stems (canes) formimpenetrable thickets several metres high.Species reproduce vegetatively and fromseed.Projected climatic suitability for theR. fruticosus agg. in 2070 (5.3 o C increasein the global average surface temperature)Climatic suitabilityhighmoderately highmoderatelikelynot suitableFigure 1.4: Climate-change modelling for theR. fruticosus agg.Root systemThe root system is the only perennial part ofthe plant. It comprises a woody crown that cangrow up to 20 centimetres in diameter and amain root that can grow down to four metres,depending on the soil type. Numerous secondaryroots grow horizontally from the crown for30 – 60 centimetres. These secondary roots thenalso grow down and further shoot thin roots inall directions.Steel et al., 2008.The method used to produce these maps differs to thatused to model the climate suitability for blackberry(see Figure 1.3, p. 13) so the results are not directlycomparable. A detailed description can be found in the fullreport at www.climatechange.vic.gov.au (go to Resources/Publications/Climate change and potential distribution ofweeds: whither the weeds under climate change?)14


Table 1.1: Lifecycle of the R. fruticosus agg. in temperate southern Australia.June July Aug Sept Oct Nov Dec Jan Feb Mar Apr MayWinter Spring Summer AutumnGerminationFlowering (2-y-o)Fruiting (2-y-o)Tip rooting (1-y-o)DormancyDark shading indicates most common timeframe for stage of life cycle. However, each stage can still occur during thelighter shaded periods.panicles with flowers and fruitfloricane orsecond year caneprimocanes or first year canesdaughter plantsuckercrown(Bruzzese and Lane, 1996)Figure 1.5: Growth pattern of R. fruticosus agg. species.17


Case studyImpact of blackberryThe problemCattle, horses and pigs introduced blackberryinto the upper reaches of the Kowmung Riverfrom nearby farms in the 1800s. Blackberryinfestations gradually spread along the river asstock moved further into the leased catchmentlands.In 1975 the Kowmung catchment became partof the Kanangra-Boyd and Blue MountainsNational Park. Stock were removed from thearea, but it was not possible to remove thosethat had become feral.Both the feral animals and the blackberryinfestations compromise the significantnatural, recreational and economic values ofthe region. In 1997 the NSW National Parks andWildlife Service (NPWS) began to implement amanagement plan to control blackberry and theferal animals.Impacts of blackberry• Competition. With few natural controls,blackberry quickly colonised disturbed areasalong the river, outcompeting native species.In the Kowmung River corridor, the maincauses of disturbed ground are fires, floodsand feral pigs.• Safe harbour. Blackberries provide harbourfor feral pigs, making it harder to undertakeaerial culling. The thickets also protect youngpigs from wild dogs, which would otherwisehelp control pig numbers.• Recreational values. Walkers along theKowmung River expect to find riverbanksand flats in their natural state. However,blackberry thickets make walking difficult,reduce the number of camping spots andcompromise the wilderness experience.• Downstream impacts. As blackberryinfestations gradually move downstream,their impact on natural and recreational valuesgrows. The weed does not confine itself tothe river but spreads up side gullies into oncepristine sub-catchments.What has been done?Initially, NPWS staff and contractors concentratedtheir blackberry control efforts on infestationslocated along the riverbanks. Because thecatchment is relatively inaccessible, they set upremote base camps for several weeks each year,targeting a 15 kilometre stretch of river. They use12‐volt electric pumps mounted on pack horsesto apply herbicide to blackberry thickets – aneffective technique, because the added height ofthe pumps allows the spray to reach the top andmiddle of the largest thickets.In the upper reaches of the river and its smallersub-catchments, NPWS staff sprayed infestationsannually using vehicle-mounted spray units andsplatter guns.By 2005, infestations along the river had beensignificantly reduced and attention turned tocontrolling upstream sources of blackberry,mostly on private property.The resultWhen the blackberry control program started,infestations along the river ranged from theoccasional individual blackberry bush tothickets that were five metres high and coveredover 300 m 2 . As a result of the NPWS programsthere are:The Kowmung River is extremely inaccessible andhad to be accessed and treated on horseback.Mikala Jones (NPWS)• no remaining large blackberry infestations.• the number of pig harbours has significantlydecreased.• pig disturbance along the river is noticeablyless, and flats once infested with blackberryare gradually regenerating with nativevegetation.• NPWS staff, contractors, bushwalkers andvolunteers report that the recreationalwilderness values of the riverine corridor havebeen enhanced.18

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