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Ranunculus inundatus, River Buttercup, is an aquatic or semi-aquatic trailing perennial, which can spread vigorously via rhizomes, to about 0.3 metres tall to several metres wide.
It has a large natural geographic distirbution in NSW, growing along the coast and tablelands, between the two borders, as far west as areas such as Bathurst, Armidale and out to Swan Hill on the Victorian border. There is a largely disjunct record well west of Dubbo. It has a fairly limited extent in Queensland, extending north to Kroombit Tops National park (south of Gladstone) and west of here (south-west of Rolleston). It is common through much of Victoria, excepting the north-west of the State. It extends into South Australia, growing northwards of Mt Gambier and around Adelaide. It grows in the very south-west corner of Western Australia – west of a line between Albany and Bunbury.
It is typically found in damp muddy soils associated with creeklines and swamps, and will also grow in water in ponds or streams.
Ranunculus spp. have leaves either simple or compound (at least usually strongly divided) and often arranged in a basal rosette. In this species, leaves are probably best described as compound, with a rounded outline to 4 cm in diameter, strongly divided into numerous segments, with segments divided again towards the terminals, resutling in linear parts about 2 mm wide, on a petiole to 20 cm long (in a similar fashion to the leaves of something like Isopogon anemonifolius); mid to dark green in colour and generally soft to the touch.
Ranunculus spp. produce solitary flowers or in cymes – with usually 5 sepals; petals can be 5 or more – yellow to white in colour with many stamens and carpels (bisexual). In this species, flowers are solitary, shiny yellow, to 2 centimetres across with 5-7 petals and held above the foliage on 30 centimetre stalks; produced from spring to summer.
The fruit is a head of achenes, each with a prominent beak. In this species, the heads consist of up to 40 achenes, each 2 mm long.
The River Buttercup may be grown on the margins of pools and dams as well as bog gardens and sites that retain moisture. It likes boggy ground at least although may tolerate some drier areas.
For maximum flowering plants need to be grown in full sun. Both foliage and flowers are attractive features.
It is a species that lends to cottage gardens and gardens with aquatic themes.
Check with native nurseries for availability.
Propagate by division.
This species may be exposed to fire in some cases and can likely regenerate from the seedbank.
Ranunculus is a large genus of about 500 species – mainly found in the temperate regions of the world. Australia has around 50 species with around 10 exotic – found in all States and Territories. NSW currently has 32 species.
Ranunculus – Latin reportedly meaning “Little Frog” (rana = frog and unculus = “small version of”) – possibly referring to the common habitat of these species.
inundatus – Latin – “inundated” / “flooded” – referring to its water-habitat.
This species is not considered to be at risk of extinction in the wild.
NSW Flora Online (PlantNET) – Ranunculus inundatus profile page https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Ranunculus~inundatus
Wrigley, J.W. & Fagg, M.I. (2001). Australian Native Plants – Propagation, cultivation and use in landscaping. 4th edition. New Holland Publishers, Pty. Ltd. Australia.
Yarra Ranges Council – Local Plant Directory – Ranunculus inundatus profile page https://www.yarraranges.vic.gov.au/PlantDirectory/Aquatic-Semi-aquatic/Ranunculus-inundatus