Acacia pycnantha

{{Short description|Golden wattle of southeastern Australia}} {{confuse |Brisbane golden wattle}} {{Use dmy dates|date=March 2021}} {{Use Australian English|date=September 2011}} {{Speciesbox | name = Golden wattle | image = Acacia pycnantha Golden Wattle.jpg | image_alt = Closeu shot pendulous green phyllodes (leaves) and yellow globular flower heads | status = LC | status_system = IUCN3.1 | status_ref = <ref name=IUCN>{{cite iucn |last1=Gowland |first1=K. |year=2022 |title=''Acacia pycnantha'' |volume=2022 |article-number=e.T200143245A200149849 |doi=10.2305/IUCN.UK.2022-1.RLTS.T200143245A200149849.en |access-date=2 February 2026}}</ref> | genus = Acacia | species = pycnantha | authority = Benth.<ref name=apni/> | synonyms = {{collapsible list|bullets = true |title=Species synonymy |''Acacia falcinella'' Meisn. |''Acacia petiolaris'' Lehm. |''Acacia pycnantha'' var. ''petiolaris'' H.Vilm. |''Acacia pycnantha'' Benth. var. ''pycnantha'' |''Acacia westonii'' Maiden |''Racosperma pycnanthum'' (Benth.) Pedley }} | synonyms_ref = <ref name=apni/> | range_map = Acacia pycnanthaDistMap739.png | range_map_caption = Occurrence data from AVH }}

'''''Acacia pycnantha''''', most commonly known as the '''golden wattle''', is a tree of the family Fabaceae. It grows to a height of {{convert|8|m|ft|abbr=off}} and has phyllodes (flattened leaf stalks) instead of true leaves. The profuse fragrant, golden flowers appear in late winter and spring, followed by long seed pods. Explorer Thomas Mitchell collected the type specimen, from which George Bentham wrote the species description in 1842. The species is native to southeastern Australia as an understorey plant in eucalyptus forest. Plants are cross-pollinated by several species of honeyeater and thornbill, which visit nectaries on the phyllodes and brush against flowers, transferring pollen between them.

''A. pycnantha'' has become a weed in areas of Australia, as well as in Africa and Eurasia. Its bark produces more tannin than any other wattle species, resulting in its commercial cultivation for production of this compound. It has been widely grown as an ornamental garden plant and for cut flower production. ''A. pycnantha'' was made the official floral emblem of Australia in 1988, and has been featured on the country's postal stamps.

==Description== [[File:Acacia pycnantha 5145.jpg|thumb|Habit, Geelong Botanic Gardens|alt=A rounded tree with green foliage and profuse yellow flowers in a public garden]] ''Acacia pycnantha'' generally grows as a small tree to between {{convert|3|and|8|m|ft|abbr=off|sigfig=1}} in height,{{sfn|Kodela|2001|p=298}} though trees of up to {{convert|12|m|ft|abbr=on|sigfig=1}} high have been reported in Morocco.<ref name="FAO">{{cite book|last=Baumer|first=Michel|title=Notes on Trees and Shrubs in Arid and Semi-arid Regions|publisher=Food & Agriculture Org.|date=1983|pages=38–39|isbn=978-92-5-101354-0|url=https://books.google.com/books?id=8g2IsYii6jsC&q=Acacia+pycnantha&pg=PA38}}</ref> The bark is generally dark brown to grey—smooth in younger plants though it can be furrowed and rough in older plants.<ref name=QLD/> Branchlets may be bare and smooth or covered with a white bloom.{{sfn|Kodela|2001|p=298}} The mature trees do not have true leaves but have phyllodes—flat and widened leaf stems—that hang down from the branches. Shiny and dark green, these are between {{convert|9|and|15|cm|in|abbr=on}} long, {{convert|1-3.5|cm|in|sigfig=1|abbr=on}} wide and falcate (sickle-shaped) to oblanceolate in shape.{{sfn|Kodela|2001|p=298}} New growth has a bronze colouration.<ref name="BirkenshawHenley2012">{{cite book|author1=Birkenshaw, Marie|author2=Henley, Claire|title=Plants of Melbourne's Western Plains: A Gardener's Guide to the Original Flora|page=72|url=https://books.google.com/books?id=MjFYLwEACAAJ|year=2012|publisher=Australian Plants Society, Keilor Plains Group|isbn=978-0-909830-65-6}}</ref> Field observations at Hale Conservation Park show the bulk of new growth occurs over spring and summer from October to January.<ref name="Vanstone 1988">{{cite journal|last=Vanstone|first=Vivien A.|author2=Paton, David C.|date=1988|title=Extrafloral Nectaries and Pollination of ''Acacia pycnantha'' Benth by Birds|journal=Australian Journal of Botany|volume=36|issue=5|pages=519–31|doi=10.1071/BT9880519 |bibcode=1988AuJB...36..519V }}</ref>

Floral buds are produced year-round on the tips of new growth, but only those initiated between November and May go on to flower several months later. Flowering usually takes place from July to November (late winter to early summer) in the golden wattle's native range, and because the later buds develop faster, flowering peaks over July and August.<ref name="buttrose">{{cite journal|last=Buttrose|first=M.S.|author2=Grant, W.J.R. |author3=Sedgley, M. |journal=Australian Journal of Botany |date=1981|title=Floral Development in ''Acacia pycnantha'' Benth. In Hook|volume=29|issue=4|pages=385–95|doi=10.1071/BT9810385 |bibcode=1981AuJB...29..385B }}</ref><ref name=NSW>{{cite web |url=http://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Acacia~pycnantha|title=''Acacia pycnantha'' Benth. |access-date=1 September 2014 |work= PlantNET – New South Wales Flora Online |publisher=Royal Botanic Gardens & Domain Trust, Sydney Australia}}</ref> The bright yellow inflorescences occur in groups of 40 to 80 on {{convert|2.5-9|cm|in|sigfig=1|abbr=on}}-long racemes that arise from axillary buds.{{sfn|Kodela|2001|p=298}} Each inflorescence is a ball-like structure covered by 40 to 100 small flowers that have five tiny petals (pentamerous) and long erect stamens, which give the flower head a fluffy appearance.<ref name=QLD/>

Developing after flowering has finished, the seed pods are flattish, straight or slightly curved, {{convert|5-14|cm|in|sigfig=1|abbr=on}} long and 5–8 mm wide.<ref name =NSW /><ref name=costermans>{{cite book|author=Costermans, Leon| title=Native Trees and Shrubs of South-eastern Australia|publisher=Rigby|location= Kent Town, South Australia | year=1981 |page=317| isbn =978-0-7270-1403-0}}</ref> They are initially bright green, maturing to dark brown and have slight constrictions between the seeds,<ref name="Simmons1987">{{cite book|author=Simmons, Marion H. |title=Acacias of Australia|date= 1987|pages=164–65|publisher=Nelson|isbn=978-0-17-007179-6}}</ref> which are arranged in a line in the pod.<ref name=NSW/> The oblong seeds themselves are 5.5 to 6 mm long, black and shiny, with a clavate (club-shaped) aril.{{sfn|Kodela|2001|p=298}} They are released in December and January, when the pods are fully ripe.<ref name="buttrose"/>

=== Similar species === Species similar in appearance include mountain hickory wattle (''A. obliquinervia''), coast golden wattle (''A. leiophylla'') and golden wreath wattle (''A. saligna'').{{sfn|Kodela|2001|p=298}} ''Acacia obliquinervia'' has grey-green phyllodes, fewer flowers in its flower heads, and broader ({{convert|1.25-2.5|cm|in|sigfig=1|abbr=on}}-wide) seed pods.{{sfn|Kodela|2001|p=251}} ''A. leiophylla'' has paler phyllodes.{{sfn|Elliot|Jones|1985|p=74}} ''A. saligna'' has longer, narrower phyllodes.<ref name="QLD" />

==Taxonomy== ''Acacia pycnantha'' was first formally described by botanist George Bentham in the ''London Journal of Botany'' in 1842.<ref name="bentham1842">{{cite journal|last=Bentham|first=George|date=1842|title=Notes on Mimoseae, with a Synopsis of Species|journal=London Journal of Botany|volume=1|page=351|url=https://www.biodiversitylibrary.org/page/10610831}}</ref> The type specimen was collected by the explorer Thomas Mitchell in present-day northern Victoria between Pyramid Hill and the Loddon River.{{sfn|Kodela|2001|p=297}}<ref name=apni>{{APNI|name =''Acacia pycnantha'' Benth.|id = 14993 }}</ref> Bentham thought it was related to ''A. leiophylla'', which he described in the same paper.<ref name="bentham1842"/> The specific epithet ''pycnantha'' is derived from the Greek words ''{{lang|grc-Latn|pyknos}}'' (dense) and ''{{lang|grc-Latn|anthos}}'' (flower), a reference to the dense cluster of flowers that make up the globular inflorescences.<ref name=boden>{{cite web | last=Boden | first= Anne| year=1985| title=Golden Wattle: Floral Emblem of Australia | work=Australian National Botanic Gardens | url=http://www.anbg.gov.au/emblems/aust.emblem.html | access-date=28 August 2007 | archive-url= https://web.archive.org/web/20070828213656/http://anbg.gov.au/emblems/aust.emblem.html| archive-date= 28 August 2007 | url-status= live}}</ref> Queensland botanist Les Pedley reclassified the species as ''Racosperma pycnanthum'' in 2003, when he proposed placing almost all Australian members of the genus into the new genus ''Racosperma''.<ref name="pedley">{{cite journal|last=Pedley|first=Les|date=2003|title=A synopsis of ''Racosperma'' C.Mart. (Leguminosae: Mimosoideae)|journal=Austrobaileya |volume=6|issue=3|pages=445–96|doi=10.5962/p.299681 |doi-access=free}}</ref> However, this name is treated as a synonym of its original name.<ref name=apni/>

Johann Georg Christian Lehmann described ''Acacia petiolaris'' in 1851 from a plant grown at Hamburg Botanic Gardens from seed said to be from the Swan River Colony (Perth).{{sfn|Kodela|2001|p=297}} Carl Meissner described ''A. falcinella'' from material from Port Lincoln in 1855. Bentham classified both as ''A. pycnantha'' in his 1864 ''Flora Australiensis'', though he did categorise a possible subspecies ''angustifolia'' based on material from Spencer Gulf with narrower phyllodes and fewer inflorescences.<ref name="Bentham 1864">{{cite encyclopedia | last= Bentham| first= George | year = 1864 | title = Acacia pycnantha | encyclopedia = Flora Australiensis | volume = 2: Leguminosae to Combretaceae | page = 365 | location = London, United Kingdom | publisher = L. Reeve & Co. | author-link = George Bentham| url=https://www.biodiversitylibrary.org/page/6781108}}</ref> However, no subspecies are currently recognised, though an informal classification distinguishes wetland and dryland forms, the latter with narrower phyllodes.<ref name="NdlovuRichardson2013">{{cite journal|last1=Ndlovu|first1=J.|last2=Richardson|first2=D. M.|last3=Wilson|first3=J. R. U.|last4=O'Leary|first4=M.|last5=Le Roux|first5=J. J.|title=Elucidating the native sources of an invasive tree species, Acacia pycnantha, reveals unexpected native range diversity and structure|journal=Annals of Botany|volume=111|issue=5|year=2013|pages=895–904|issn=0305-7364|doi=10.1093/aob/mct057|pmid=23482331|pmc=3631341}}</ref>

In 1921 Joseph Maiden described ''Acacia westonii'' from the northern and western slopes of Mount Jerrabomberra near Queanbeyan in New South Wales. He felt it was similar to, but distinct from, ''A. pycnantha'' and was uncertain whether it warranted species rank. His colleague Richard Hind Cambage grew seedlings and reported they had much longer internodes than those of ''A. pycnantha'', and that the phyllodes appeared to have three nectaries rather than the single one of the latter species.<ref>{{cite journal|last=Maiden|first=Joseph Henry|date=1921|title=Notes on Two Acacias|journal=Journal and Proceedings of the Royal Society of New South Wales|volume=54|pages=227–30|doi=10.5962/p.359778 |s2cid=259739003 |url=https://www.biodiversitylibrary.org/page/41869385|doi-access=free}}</ref> It is now regarded as a synonym of ''A. pycnantha''.<ref name=apni/>

Common names recorded include golden wattle, green wattle, black wattle, and broad-leaved wattle.<ref name=apni/> At Ebenezer Mission in the Wergaia country of north-western Victoria the Aboriginal people referred to it as ''witch''.<ref name="Maiden1890">{{cite book|author=Maiden, Joseph Henry|title=Wattles and wattlebarks of New South Wales|publisher=Charles Potter|location=Sydney, New South Wales |url=http://adc.library.usyd.edu.au/data-2/p00111.pdf}}</ref><ref name="Clark1995">{{cite book|author= Clark, Ian|title=Scars in the Landscape: Hidden Aboriginal History in Western Victoria|url=https://books.google.com/books?id=N0dIhJqRqYgC&pg=PA177|date= 1995|publisher=Aboriginal Studies Press|isbn=978-0-85575-595-9|page=177}}</ref>

Hybrids of the species are known in nature and cultivation. In the Whipstick forest near Bendigo in Victoria, putative hybrids with Whirrakee wattle (''Acacia williamsonii'') have been identified; these resemble hakea wattle (''Acacia hakeoides'').{{sfn|Kodela|2001|p=298}} Garden hybrids with Queensland silver wattle (''Acacia podalyriifolia'') raised in Europe have been given the names ''Acacia x siebertiana'' and ''Acacia x deneufvillei''.<ref name=apni/>

==Distribution and habitat== [[File:Galls on Acacia pycnantha.jpg|thumb|Galls formed by ''Trichilogaster signiventris'' wasps on a plant in South Africa|alt=Round green ball-like galls among green phyllodes (leaves)]] Golden wattle occurs in south-eastern Australia from South Australia's southern Eyre Peninsula and Flinders Ranges across Victoria and northwards into inland areas of southern New South Wales and the Australian Capital Territory.<ref name =NSW /><ref name=RBG>{{cite web|title=''Acacia pycnantha'' Benth.|work=Flora of Victoria Knowledge Base|publisher=Royal Botanic Gardens Melbourne|url=http://www.rbg.vic.gov.au/dbpages/dev/vicflora/index.php/viclist/name/80|archive-url=https://archive.today/20140902112530/http://www.rbg.vic.gov.au/dbpages/dev/vicflora/index.php/viclist/name/80|url-status=dead|archive-date=2 September 2014|access-date=6 June 2014}}</ref> It is found in the understorey of open eucalypt forests on dry, shallow soils.<ref name=costermans/>

The species has become naturalised beyond its original range in Australia. In New South Wales it is especially prevalent around Sydney and the Central Coast region. In Tasmania it has spread in the east of the state and become weedy in bushland near Hobart. In Western Australia, it is found in the Darling Range and western wheatbelt as well as Esperance and Kalgoorlie.<ref name=QLD>{{cite web|title=Golden Wattle ''Acacia pycnantha''|work=Weeds of Australia: Biosecurity Queensland Edition|publisher=Queensland Government|url=http://keyserver.lucidcentral.org/weeds/data/03030800-0b07-490a-8d04-0605030c0f01/media/Html/Acacia_pycnantha.htm|access-date=31 August 2014|archive-date=4 March 2016|archive-url=https://web.archive.org/web/20160304235146/http://keyserver.lucidcentral.org/weeds/data/03030800-0b07-490a-8d04-0605030c0f01/media/Html/Acacia_pycnantha.htm|url-status=dead}}</ref>

Outside Australia it has become naturalised in South Africa where it is considered an invasive alien plant and is uprooted to prevent water depletion and protect local flora, Tanzania, Italy, Portugal, Sardinia, India, Indonesia and New Zealand.<ref name=QLD/> It is present in California as a garden escapee, but is not considered to be naturalised there.<ref name=jepson>{{cite web|title=''Acacia pycnantha'' Benth.|work=Jepson Flora Project|url=http://ucjeps.berkeley.edu/cgi-bin/get_cpn.pl?11660&expand=1|access-date=2 September 2014}}</ref> In South Africa, where it had been introduced between 1858 and 1865 for dune stabilization and tannin production, it had spread along waterways into forest, mountain and lowland fynbos, and borderline areas between fynbos and karoo.<ref name="dennill 1991">{{cite journal|last1=Dennill|first1=G. B.|last2=Gordon|first2=A. J.|date=1991|title=''Trichilogaster'' sp. (Hymenoptera: Pteromalidae), a potential biocontrol agent for the weed ''Acacia pycnantha'' (Fabaceae)|journal=Entomophaga|volume=36|issue=2|pages=295–301|doi=10.1007/BF02374565|bibcode=1991BioCo..36..295D |s2cid=25527017}}</ref> The gall-forming wasp ''Trichilogaster signiventris'' has been introduced in South Africa for biological control and has reduced the capacity of trees to reproduce throughout their range.<ref name="MuniappanReddy2009p47">{{cite book|author1= Muniappan, Rangaswamy|author2=Reddy, Gadi V. P. |author3= Raman, Anantanarayanan|title=Biological Control of Tropical Weeds Using Arthropods|url=https://books.google.com/books?id=CDECHl8qhsIC&pg=PA47|year=2009|publisher=Cambridge University Press|isbn=978-0-521-87791-6|page=47}}</ref> The eggs are laid by adult wasps into buds of flower heads in the summer, before hatching in May and June when the larvae induce the formation of the grape-like galls and prevent flower development. The galls can be so heavy that branches break under their weight.<ref name="hoffmann 2002">{{cite journal|last1=Hoffmann|first1=J. H.|last2=Impson|first2=F. A. C.|last3=Moran|first3=V. C.|last4=Donnelly|first4=D.|date=2002|title=Biological Control of Invasive Golden Wattle Trees (''Acacia pycnantha'') by a gall wasp, ''Trichilogaster'' sp. (Hymenoptera: Pteromalidae), in South Africa|journal=Biological Control|volume=25|issue=1|pages=64–73|doi=10.1016/s1049-9644(02)00039-7|bibcode=2002BiolC..25...64H }}</ref> In addition, the introduction in 2001 of the acacia seed weevil ''Melanterius compactus'' has also proved effective.<ref name="CullenJulien2012">{{cite book|author1=Cullen, Jim |author2=Julien, Mic |author3=McFadyen, Rachel |title=Biological Control of Weeds in Australia due to the extreme levels of Ultra Vioket light.|url=https://books.google.com/books?id=qe9xnWc0oIwC&pg=PA7|year= 2012|publisher=CSIRO Publishing|page=7|isbn=978-0-643-10421-1}}</ref>

==Ecology== thumb|A fly visiting a nectary on a phyllode|alt=a fly perched on a phyllode Though plants are usually killed by a severe fire, mature specimens are able to resprout.<ref name=florabank>{{cite web|title=Acacia pycnantha|work=florabank|publisher=Greening Australia|url=http://www.florabank.org.au/lucid/key/species%20navigator/media/html/Acacia_pycnantha.htm|access-date=2 September 2014|archive-date=10 March 2015|archive-url=https://web.archive.org/web/20150310011500/http://florabank.org.au/lucid/key/Species%20Navigator/Media/Html/Acacia_pycnantha.htm|url-status=dead}}</ref><ref name=WA>{{FloraBase|name=''Acacia pycnantha'' Benth. |id=3504 }}</ref> Seeds are able to persist in the soil for more than five years, germinating after fire.<ref name=WA/>

Like other wattles, ''Acacia pycnantha'' fixes nitrogen from the atmosphere.<ref>{{cite web|url=http://www.florabank.org.au/lucid/key/species%20navigator/media/html/Acacia_pycnantha.htm|title=Acacia pycnantha|last=Greening Australia|date=2010|work=Florabank|publisher=Australian Government/Greening Australia/CSIRO|access-date=10 October 2014|location=Yarralumla, Australian Capital Territory|archive-date=10 March 2015|archive-url=https://web.archive.org/web/20150310011500/http://florabank.org.au/lucid/key/Species%20Navigator/Media/Html/Acacia_pycnantha.htm|url-status=dead}}</ref> It hosts bacteria known as rhizobia that form root nodules, where they make nitrogen available in organic form and thus help the plant grow in poor soils. A field study across Australia and South Africa found that the microbes are genetically diverse, belonging to various strains of the species ''Bradyrhizobium japonicum'' and genus ''Burkholderia'' in both countries. It is unclear whether the golden wattle was accompanied by the bacteria to the African continent or encountered new populations there.<ref>{{cite journal|last=Rodríguez-Echeverría|first=Susana|author2=Le Roux, Johannes J.|author3=Crisóstomo, João A.|author4=Ndlovu, Joice |date=2011|title=Jack-of-all-trades and master of many? How does associated rhizobial diversity influence the colonization success of Australian ''Acacia'' species?|journal=Diversity and Distributions|volume=17|issue=5|pages=946–57|doi=10.1111/j.1472-4642.2011.00787.x|doi-access=|bibcode=2011DivDi..17..946R }}</ref>

Self-incompatible, ''A. pycnantha'' cannot fertilise itself and requires cross-pollination between plants to set seed.<ref>{{cite journal|last=Kenrick|first=J.|author2=Knox, R.B. |date=1988|title=Quantitative Analysis of Self-Incompatibility in Trees of Seven Species of Acacia|journal=Journal of Heredity|volume=80|issue=3|pages=240–45|issn=0022-1503|doi=10.1093/oxfordjournals.jhered.a110842}}</ref> Birds facilitate this and field experiments keeping birds away from flowers greatly reduces seed production. Nectaries are located on phyllodes; those near open flowers become active, producing nectar that birds feed upon just before or during flowering. While feeding, birds brush against the flower heads and dislodge pollen and often visit multiple trees.<ref name="Vanstone 1988"/> Several species of honeyeater, including the white-naped, yellow-faced,<ref name="ford 76">{{cite journal|last=Ford|first=Hugh A.|author2=Forde, Neville |date=1976|title=Birds as Possible Pollinators of ''Acacia pycnantha''|journal=Australian Journal of Botany|volume=24|issue=6|pages=793–95|doi=10.1071/BT9760793 |bibcode=1976AuJB...24..793F }}</ref> New Holland,<ref>{{cite book|title=Corella|url=https://books.google.com/books?id=VJZKAAAAYAAJ|year=1998|publisher=Australian Bird Study Association}}</ref> and occasionally white-plumed and crescent honeyeaters,<ref name="ford 76"/> and eastern spinebills have been observed foraging. Other bird species include the silvereye, striated, buff-rumped and brown thornbills. As well as eating nectar, birds often pick off insects on the foliage. Honeybees, native bees, ants and flies also visit nectaries, but generally do not come into contact with the flowers during this activity.<ref name="Vanstone 1988"/> The presence of ''A. pycnantha'' is positively correlated with numbers of swift parrots overwintering in box–ironbark forest in central Victoria, though it is not clear whether the parrots are feeding on them or some other factor is at play.<ref>{{cite journal|last=Mac Nally|first=Ralph |author2=Horrocks, Gregory |date=2000|title=Landscape-scale Conservation of an Endangered Migrant:the Swift Parrot (''Lathamus discolor'') in its Winter Range|journal=Biological Conservation|volume=92|issue=3|pages=335–43|doi=10.1016/S0006-3207(99)00100-7|bibcode=2000BCons..92..335M }}</ref>

The wood serves as food for larvae of the jewel beetle species ''Agrilus assimilis'', ''A. australasiae'' and ''A. hypoleucus''.<ref>{{cite book|author1=Jendek, Eduard |author2=Poláková, Janka |title=Host Plants of World ''Agrilus'' (Coleoptera, Buprestidae)|publisher=Springer|location=New York, New York|date=2014|page=455|isbn=978-3-319-08410-7|url=https://books.google.com/books?id=JgZYBAAAQBAJ&q=Acacia+pycnantha&pg=PA50}}</ref> The larvae of a number of butterfly species feed on the foliage including the fiery jewel, icilius blue, lithocroa blue and wattle blue.<ref name=SA>{{cite web | url =http://www.flora.sa.gov.au/cgi-bin/speciesfacts_display.cgi?form=speciesfacts&family=&genus=acacia&species=pycnantha&iname=&submit=Display | title = Acacia pycnantha |access-date = 1 September 2014 |work = Electronic Flora of South Australia Fact Sheet | publisher = State Herbarium of South Australia }}</ref> ''Trichilogaster'' wasps form galls in the flowerheads, disrupting seed set<ref name="MaslinMcDonald2004">{{cite book|author1=Maslin, Bruce Roger |author2=McDonald, Maurice William |title=AcaciaSearch: Evaluation of Acacia as a Woody Crop Option for Southern Australia|url=http://www.worldwidewattle.com/infogallery/utilisation/acaciasearch/pdf/pycnantha.pdf|year=2004|publisher=Rural Industries Research and Development Corporation|isbn=978-0-642-58585-1}}</ref> and ''Acizzia acaciaepycnanthae'', a psyllid, sucks sap from the leaves.<ref name=fao>{{cite web|author1=Old, K.M. |author2=Vercoe, T.K. |author3=Floyd, R.B. |author4=Wingfield, M.J. |title=FAO/IPGRI Technical Guidelines for the Safe Movement of Germplasm No. 20 ''Acacia'' sp.|publisher=Food and Agriculture Organization of the United Nations/International Plant Genetic Resources Institute|year=2002|page=24|url=http://www.bioversityinternational.org/uploads/tx_news/Acacia_spp._829.pdf|access-date=15 September 2014}}</ref> ''Acacia pycnantha'' is a host to rust fungus species in the genus ''Uromycladium'' that affect the phyllodes and branches. These include ''Uromycladium simplex'' that forms pustules and ''U. tepperianum'' that causes large swollen brown to black galls, which eventually lead to the death of the host plant.<ref name="McAlpine 1906">{{cite book|author=McAlpine, Daniel|title=The rusts of Australia their structure, nature and classification|publisher=Department of Agriculture (Victoria)|year=1906|pages=110–12|url=https://www.biodiversitylibrary.org/page/23538426}}</ref><ref name=USDA>{{cite web|title=''Uromycladium tepperianum'' on ''Acacia'' spp.|work=Invasive and Emerging Fungal Pathogens – Diagnostic Fact Sheets|publisher=United States Department of Agriculture|url=http://nt.ars-grin.gov/taxadescriptions/factsheets/index.cfm?thisapp=Uromycladiumtepperianum|access-date=2 September 2014|url-status=dead|archive-url=https://web.archive.org/web/20140903151338/http://nt.ars-grin.gov/taxadescriptions/factsheets/index.cfm?thisapp=Uromycladiumtepperianum|archive-date=3 September 2014}}</ref> Two fungal species have been isolated from leaf spots on ''A. pycnantha'': ''Seimatosporium arbuti'', which is found on a wide range of plant hosts, and ''Monochaetia lutea''.<ref>{{cite journal|last=Swart|first=H.J.|author2=Griffiths, D.A. |date=1974|title=Australian Leaf-inhabiting Fungi: IV. Two Coelomycetes on ''Acacia pycnantha''|journal=Transactions of the British Mycological Society|volume=62|issue=1|pages=151–61|doi=10.1016/S0007-1536(74)80016-1}}</ref>

== Cultivation == Golden wattle is cultivated in Australia and was introduced to the northern hemisphere in the mid-1800s. Although it has a relatively short lifespan of 15 to 30 years, it is widely grown for its bright yellow, fragrant flowers.<ref name="boden" /><ref name="MaslinMcDonald2004" /> As well as being an ornamental plant, it has been used as a windbreak or in controlling erosion. Trees are sometimes planted with the taller sugar gum (''Eucalyptus cladocalyx'') to make a two-layered windbreak.<ref name="FAO" /> One form widely cultivated was originally collected on Mount Arapiles in western Victoria. It is floriferous, with fragrant flowers appearing from April to July.{{sfn|Elliot|Jones|1985|p=103}} The species has a degree of frost tolerance and is adaptable to a wide range of soil conditions, but it prefers good drainage.{{sfn|Elliot|Jones|1985|p=103}} It tolerates heavy soils in dry climates,<ref>{{cite journal |last=Lothian |first=T.R.N. |date=1969 |title=Gardening in the Low Rainfall Regions |journal=Australian Plants |volume=5 |issue=38 |pages=54–55, 80–95 [89]}}</ref> as well as mild soil salinity.<ref>{{cite journal |last=Zwar |first=J. |date=1975 |title=Trees in Dry Areas |journal=Australian Plants |volume=8 |issue=64 |pages=164–67 [165]}}</ref> It can suffer yellowing (chlorosis) in limestone-based (alkaline) soils.<ref name="FAO" /> Highly drought-tolerant, it needs {{convert|370-550|mm|in|sigfig=1|abbr=on}} winter rainfall for cultivation.<ref name="FAO" /> It is vulnerable to gall attack in cultivation.<ref name="holliday">{{cite book |last=Holliday |first=Ivan |title=A Field Guide to Australian Trees |date=1989 |publisher=Hamlyn |isbn=978-0-947334-08-6 |edition=2nd |location=Port Melbourne, Victoria |page=28}}</ref> Propagation is from seed which has been pre-soaked in hot water to soften the hard seed coating.<ref name="boden" />

==Uses== thumb|Trunk exuding gum|alt=closeup of trunk and bark with single point showing oozing transparent golden gum-like substance Golden wattle has been grown in temperate regions around the world for the tannin in its bark, as it provides the highest yield of all wattles.<ref name=boden/> Trees can be harvested for tannin from seven to ten years of age.<ref name="FAO"/> Commercial use of its timber is limited by the small size of trees, but it has high value as a fuel wood.<ref name="MaslinThomson1998">{{cite book|author1=Maslin, B.R. |author2=Thomson, L.A.J. |author3=McDonald. M.W. |author4=Hamilton-Brown, S.|title=Edible Wattle Seeds of Southern Australia: A Review of Species for Use in Semi-Arid Regions|url=https://books.google.com/books?id=LWe7PjFrlg8C&pg=PT44|date=1998|publisher=CSIRO Publishing|isbn=978-0-643-10253-8|page=44}}</ref> The scented flowers have been used for perfume making,<ref name=boden/> and honey production in humid areas. However, the pollen is too dry to be collected by bees in dry climates.<ref name="FAO"/> In southern Europe, it is one of several species grown for the cut-flower trade and sold as "mimosa".<ref name="WWWuses">{{cite web|title=Wattle uses|work=World Wide Wattle|url=http://www.worldwidewattle.com/schools/uses.php|access-date=1 September 2014}}</ref> Like many other species of wattle, ''Acacia pycnantha'' exudes gum when stressed.<ref name=Annison/> Eaten by indigenous Australians, the gum has been investigated as a possible alternative to gum arabic, commonly used in the food industry.{{sfn|Kodela|2001|p=298}}<ref name=Annison>{{cite journal|author1=Annison, Geoffrey |author2=Trimble, Rodney P. |author3=Topping, David L. |title=Feeding Australian Acacia Gums and Gum Arabic Leads to Non-Starch Polysaccharide Accumulation in the Cecum of Rats|pages=283–92|volume=125|issue=2 |journal=Journal of Nutrition|url=http://jn.nutrition.org/content/125/2/283.full.pdf|doi=10.1093/jn/125.2.283 |pmid=7861255 |year=1995 }}</ref>

==In culture== thumb|Golden wattle in full flower|alt=Green leaves and numerous small yellow round flowerheads against the sky Wattles, and in particular the golden wattle, have been an informal floral emblem of Australia for many years (for instance, it represented Australia on the Coronation gown of Queen Elizabeth II in 1953). While some advocates forcefully argued for the adoption of the waratah, during Australia's bicentenary in 1988 the golden wattle was formally adopted as the floral emblem of Australia.<ref>{{Cite web |last=White |first=Richard |date=2021 |title=The slippery symbols of Australia |url=https://www.sl.nsw.gov.au/stories/slippery-symbols-australia |access-date= |website=State Library of New South Wales}}</ref> This was proclaimed by governor-general Sir Ninian Stephen (on the advice of the Hawke government) in the Commonwealth gazette published on 1 September.<ref name=gaz>{{cite web | author=Stephen, Ninian| year=1988| title=Proclamation of ''Acacia pycnantha'' as the Floral Emblem of Australia | work=Australian National Botanic Gardens | url=http://anbg.gov.au/emblems/ac.pyc.gaz.html | access-date=11 September 2014 | archive-url= https://web.archive.org/web/20070905035902/http://anbg.gov.au/emblems/ac.pyc.gaz.html | archive-date=5 September 2007 | url-status= live}}</ref> The day was marked by a ceremony at the Australian National Botanic Gardens, which included the planting of a golden wattle by Hazel Hawke, the prime minister's wife. In 1992, 1 September was formally declared "National Wattle Day".<ref name=boden/>

The Australian Coat of Arms includes a wreath of wattle; this does not, however, accurately represent a golden wattle. Similarly, the green and gold colours used by Australian international sporting teams were inspired by the colours of wattles in general, rather than the golden wattle specifically.<ref name=boden/>

The species was depicted on a stamp captioned "wattle" as part of a 1959–60 Australian stamp set featuring Australian native flowers. In 1970, a 5c stamp labelled "Golden Wattle" was issued to complement an earlier set depicting the floral emblems of Australia. To mark Australia Day in 1990, a 41c stamp labelled "Acacia pycnantha" was issued.<ref name=boden/> Another stamp labelled "Golden Wattle", with a value of 70c, was issued in 2014.<ref>{{cite web|title=Plant:''Acacia pycnantha''|work=Australian Plants on Stamps|publisher=Australian National |url=http://www.anbg.gov.au/stamps/stamp-acacia-pycnantha-2014.html|access-date=1 September 2014}}</ref>

Clare Waight Keller included golden wattles to represent Australia in Meghan Markle's wedding veil, which included the distinctive flora of each Commonwealth country.<ref>{{cite web|url=https://www.royal.uk/wedding-dress-bridesmaids%E2%80%99-dresses-and-page-boys-uniforms|title=The Wedding Dress: Clare Waight Keller for Givenchy|date=19 May 2018|publisher=The Royal Household, UK}}</ref>

The 1970 ''Monty Python's Flying Circus'' Bruces sketch includes a reference, by one of the stereotyped Australian characters, to "the wattle" as being "the emblem of our land", with suggested methods of display, including "stick[ing] it in a bottle or hold[ing] it in your hand" — despite the wattle prop itself being a large, forked branch with sparse patches of leaves and generic yellow flowers.

==See also== {{wikispecies|Acacia pycnantha}} {{commons}} *List of flora on stamps of Australia {{Clear}}

==References== {{Reflist|30em}}

===Cited texts=== *{{cite book | last1=Elliot | first1=Rodger W. | last2=Jones | first2=David L. | last3=Blake | first3=Trevor |title=Encyclopaedia of Australian Plants Suitable for Cultivation | volume = 2 |year=1985 |publisher=Lothian Press |location=Port Melbourne, Victoria |isbn=978-0-85091-143-5|ref={{sfnRef|Elliot|Jones|1985}} }} *{{cite encyclopedia | last=Kodela | first= Phillip G. | year = 2001| title = Acacia |editor1=Wilson, Annette |editor2=Orchard, Anthony E. | encyclopedia = Flora of Australia | volume = 11A, 11B, Part 1: Mimosaceae, Acacia | publisher = CSIRO Publishing / Australian Biological Resources Study | isbn = 978-0-643-06718-9 | url=https://books.google.com/books?id=ejr44b2rnjQC&q=Acacia+parramattensis&pg=PA610}} {{Wikispecies}} {{Commonscat}}

pycnantha Category:Fabales of Australia Category:Flora of New South Wales Category:Flora of South Australia Category:Flora of the Australian Capital Territory Category:Flora of Victoria (state) Category:National symbols of Australia Category:Trees of Australia Category:Plants described in 1842