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CYTISUS SCOPARIUS (SCOTCH BROOM) IN WESTERN AUSTRALIA By GREG KEIGHERY Science Division, Department of Environment and Conservation, Locked Bag 104, Bentley Delivery Centre, Western Australia, 6983. Email: [email protected] ABSTRACT Cytisus scoparius, a weed of National Significance was recorded as naturalised in Western Australia for the first time around the Wellington Dam and along the Collie River in 2010. Immediate action by the DEC staff from Collie District has resulted in the removal of nearly all plants and set the stage for the likely eradication of this species in the wild in Australia. INTRODUCTION including the closely related Tagasaste or Tree Lucerne Cytisus scoparius (L.) Link, of the (Chamaecytisus palmensis), pro¬ family Fabaceae, is a member of a moted as a fodder plant in group of closely related genera of Western Australia and the White long branched green stemmed Spanish broom (Cytisus shrubs with racemes of yellow multiflorus). flowers commonly referred to as Brooms native to the Northern Other less closely related Brooms Hemisphere. Cytisus scoparius naturalised in Australia (Vic¬ which has several common torian Department of Primary names including, Scotch, English Industries 2011) are Montpellier or Common Broom, is native to Broom (Genista monspessulana), Europe from the Ukraine to Flax-Leaved Broom (Genista Ireland, south to Spain and north linifolia), Madeira Broom (Genista to Sweden. The species is widely stenopetala), Spanish Broom cultivated and has become a (Spartium junceum), Canary Island weed of temperate areas of Stick Broom (A denocarpus western USA, Hawaii, Canada complicatus) and White Broom (British Columbia), Australia, (Retama raetum). New Zealand, Iran, India and Five Brooms are recorded as South Africa (Hosking et al. 1998). naturalised in Western Australia At present a series of other (Hussey et al 2007). These are: species within the Brooms are A denocarpus complicatus, also naturalised in Australia, Chamaecytisus palmensis, Genista 269 linifolia, Genista monspessulana very serious weed species in and Retama raetum. The last three Western Australia. species being the most invasive environmental weeds. Occas¬ ional feral plants and small RESULTS populations of another three During surveys of the flora of Brooms Genista horrida, Spartium Wellington National Park in junceum and Genista florida have 2009/10 scattered plants of also been recorded by me but are Cytisus scoparius were located in not yet fully naturalised in the National Park along the Western Australia. banks of the Collie River. Upon Cytisus scoparius is currently re¬ tracing these occurrences up¬ corded as naturalised in Australia stream towards the Wellington in the Australian Capital Ter¬ Dam a large population of the ritory, New South Wales, weed was located in the Victoria, Tasmania and South Wellington Dam Tourist Pre¬ Australia. Within these juris¬ cinct. This population is not dictions major infestations occur mentioned in the Management in eastern New South Wales Plan for the area (Conservation (especially Barrington Tops, Commission of Western Aus¬ Shoalhaven River Catchment, tralia 2008), nor on the local Kosciuszko National Park and Flora (Wheeler, et al. (2002). There the Blue Mountains area), and in are no records of Cytisus scoparius Victoria, over 150,000 hectares of naturalised in Western Australia land in Victoria’s central high¬ on Florabase or the Australian land and alpine regions. These Virtual Herbarium (Western infestations have led to this Australian Herbarium 1998). species being nominated and While most plants were yellow subsequently accepted as a Weed flowered (voucher G. Keighery of National Significance (Vic¬ 17639), red and yellow flowered torian Department of Primary plants (voucher G. Keighery Industries 2011) in 2012. 17640) were also present in the Cytisus scoparius has never been area. The latter plants are recorded as naturalised in West¬ described by Hosking et al. (2000) ern Australia, despite being freely as “Red and yellow flowered available in the nursery trade hybrids (i.e. horticultural and widely grown. However, selections from hybrids between much of the lower South-West is Cytisus scoparius and other Cytisus modelled as a very favourable / Genista species) similar to the climatic zone (Victorian Depart¬ cultivars Andreanus and ment of Primary Industries 2011) Andreanus Yellow have become for the species. naturalized in New South Wales, This brief note documents the Victoria and Tasmania)”. discovery and subsequent at¬ Apparently at least two separate tempt to remove this potentially plantings/introductions were 270 made into the area giving rise to follow the contours and prevent the two colour forms recorded. removal of trees, and the toilets were blended into the The populations along the Collie River and Wellington National surrounding bushland. Park apparently date from Oldham directed that plantings sometime after 1960 when Public were, therefore, native species Works Architect John Oldham except in the Quarry (PWD file, was engaged to landscape the Wellington Dam, landscaping & area around the northern side of buildings, State Records Office the enlarged dam and the large Western Australia, WAS 3035 quarry (called the Wellington CONS 1869, Item 1960/0424; Dam Precinct) which had been Oldham, op cit, list of native used to provide material for the plants sourced from Yilgarnia dam. Nursery). Flowering species for Oldham stated “We screened and the carpark and toilet surrounds protected the quarry by a natural included some 570 kangaroo paw stone wall around the top - this (Anigozanthos sp.) of various will guide visitors toward a new colour, Crowea dentata, Black lookout designed to project from Wattle (Acacia decurrens), a the hillside pointing firmly back groundcover (Lechenaultia biloba), at the dam. The walls of the and bottlebrush (Callistemon sp, quarry were scaled down. It was stated as phoenicus), as well as 70 back filled with good soil, Karri (likely the Karri Hazel planted with lawn and trees, Trymalium odoratissimum). Obvi¬ furnished with shelters and ously a broad definition of barbeques and became a hazard native to Australia was used to free picnic area.... the lozenge define native species. shaped shelters deliberately echo After establishment of the the viewing platform and Dam viewing area in 1960, a caretaker’s in shape and materials. Most trees quarters and kiosk/cafe were in the quarry are deciduous to let constructed in 1966, following the sun through in winter. The requests for more public quarry was popular from the facilities. It was probably during start - it came into use the 1970 -1990 period when the immediately after completion” original plantings had senesced (Oldham, John, ‘Landscape of or died (the cafe was also closed water resources’, unpublished for several years for two periods speech, held at Heritage Council over this time) that the Cytisus of Western Australia Library). were obtained and planted Other aspects of the landscaping during attempts at refurbish¬ design included a lookout at the ment of the gardens. By this time top of the dam, car parks, toilets the original concept of planting and a new zigzag road that took mainly ?local native species in visitors below the Dam. The the precinct had been lost and parking areas were designed to only sporadic maintenance was 271 occurring. A complete list of when it washes up on the bank. plants present in the Wellington Subsequent to the discovery of Dam precinct has been compiled this population, DEC staff from by me and will be presented as an Collie carried out control annotated list in the planned measures on the area following paper on the flora of Wellington techniques outlined in Hosking National Park. et al. (2000) which has resulted in The oldest Cytisus plants present the cutting down / spraying of all were not now in any garden site adult plants and juveniles and from their size were prob¬ resulting in the destruction of ably under 20 years old, sug¬ over 95% of the population. 1 gesting that the original garden have removed any plants located plantings had also died or been along the river. It is encouraging lost. Downey and Smith (2000) to note that significant progress have noted that individuals may has been made on eradicating a live for over 30 years, but reach potential serious environmental heights of over 6 metres in that weed immediately after its time! discovery. There were plants of Cytisus all However, Downey and Smith around the margins of the car (2000), Hosking et al (1998) and park spreading down slope into Bossard (2000) note that this the adjacent Jarrah-Marri Wood¬ species produces some 8-15,000 lands and onto granite slopes seeds per adult plant per year above the dam which are dom¬ which can remain viable for at inated by low heaths of least 5 (and up to 30) years in the Verticordia and Calytrix species soil, so continual monitoring of grading into tall Acacia shrub- the Park will be vital for many lands. Population size of the years weed was over 100 mature plants with numerous juveniles. Scat¬ CONCLUSIONS tered plants were located along the river edge in Eucalyptus rudis The discovery of this population woodland below the granite of Scotch Broom highlights the cliffs below the dam and for need for surveillance and early several kilometres downstream. control efforts for these po¬ In eastern Australia the species is tentially serious weeds. Most known to be an aggressive water supply dams had gardens invader of fertile relatively open established around their look¬ sites, such as granite soils and outs and these should be riverine edges. Smith (2000) surveyed for more populations noted that the seed can be of this weed. It also illustrates the carried long distances in the bed need for vigilance in the plant¬ load of rivers, where scouring in ing of such species within the stream bed may scarify the natural environments and the seed preparing it for germination need for removal and replace- 272 ment by more benign species of HOSKING, J.R., SHEPPARD, A.W. all Brooms from the Australian and SMITH, J.M.B. 2000. Best nursery trade. Practice Management Guide, Broom, Cytisus scoparius. Co¬ operative Research Centre for REFERENCES Weed Management Systems, Adelaide. BOSSARD, C. C. 2000. Cytisus scoparius (L.) Link. In: Bossard, CC, HUSSEY, B.M.J., KEIGHERY, G.J., Randall, J.M., Hoshovsky, M.C. DODD, J., LLOYD, S.G. and (eds.). Invasive Plants of California’s COUSENS, R.D. 2007. Western Wildlands. University of California Weeds. Plant Protection Society, Press, Berkeley. Perth. CONSERVATION COMMISSION SMITH, J.M.B. 2000. An intro¬ OF WESTERN AUSTRALIA 2008. duction to the biogeography and Wellington National Park, ecology of broom Cytisus scoparius Westralia Conservation Park and (L.) Link in Australia. Plant Wellington Discovery Forest. Protection Quarterly 15:140-144. Management Plan. Department of VICTORIAN GOVERNMENT Environment and Conservation, DEPARTMENT of PRIMARY Perth. INDUSTRIES. 2011. English Broom, DOWNEY, P.O. and SMITH, J.M.B. Scotch Broom, Broom, Cytisus 2000. Demography of the invasive scoparius (L.) Link. Weed of shrub Scotch Broom (Cytisus National Significance Nomin¬ scoparius) at Barrington Tops, New ation. South Wales: insights for WESTERN AUSTRALIAN management. Austral Ecology 25: HERBARIUM 1998-. FloraBase - 477-485. The Western Australian Flora. HOSK1NG, J.R., SMITH, J.M.B. and Department of Environment and SHEPPARD, A.W. 1998. Cytisus Conservation. Available at http:/ / scoparius (L.) Link subsp. scoparius. florabase.dec.wa.gov.au/. 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