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Oenanthe pimpinelloides

Description
 

Water Dropwort (Oenanthe pimpinelloides) is an erect perennial herb growing 30-100 cm high. It has a solid, striated stem that branches, and its roots have rounded tubers towards their ends. There are two types of leaves. The basal leaves are 2-pinnate (twice-divided) with wedge- (narrow-triangular), lance- or ovate-shaped segments 2-7 mm long and lobed. The stem-leaves are 1- or 2-pinnate with very narrow lance-shaped to linear segments 1-3 cm long and usually entire. The leaves generally become longer and narrower up the stems (Eichler 1986; Duretto 1999).

The umbel-shaped flower-heads are at the end of the stems, 2-5 cm in diameter, with a peduncle or main stalk 4-12 cm long. There several narrow-triangular, gradually tapered involucral bracts (modified leaves arranged in whorls from which the flower or flower stalk arises) at the base of the umbel. From this base there are 6-15 rays or minor stalks 0.5-6 cm long, radiating up like an inverted umbrella frame (these thicken when fruiting) and at their ends are umbellules (or smaller inverted umbrella frames) composed of 10-20 or more, crowded, short-stalked small flowers with white petals 1-2 mm long. At the base of the flowers there are 3-6 narrowly triangular to ovate scales (called bracteoles) 2-4 mm or more long (Eichler 1986; Duretto 1999).

The cylindrical fruit is about 3 mm long, strongly ribbed, and can appear spined with stiff points at the apex due to the persistent sepals and erect stigmas (Eichler 1986; Duretto 1999).

For further information and assistance with identification of Water Dropwort contact the herbarium in your state or territory.

Distribution:

There are few naturalised records of Water Dropwort in Australia; however, it has the potential to spread further. It is currently known in South Australia from the Meadows area in the Mount Lofty Ranges. In Victoria it is known only from Shepparton State Forest (where it was common in 1980), and near Wonthaggi (where a few plants were noted in 1996) (Duretto 1999).

The overseas distribution indicates Water Dropwort could establish in southern temperate Australia, especially in wet areas in south-western Western Australia, southern Victoria, south-eastern New South Wales, and Tasmania (see Cunningham & Brown 2006 and their cited references).

Habit:Herb
Key points:
  • Water Dropwort (Oenanthe pimpinelloides) is an erect herb with parsley- or fennel-like foliage and clusters of small white flowers.
  • It is spread by seed and root tubers.
  • There is good potential for eradicating or controlling this species.
How it spreads:

Water Dropwort is dispersed by seed and vegetatively by root tubers. Dispersal is promoted by reproduction from the tubers, and by seeds floating in watercourses (Shepherd 2004).

Where it grows:

Water Dropwort grows in moist meadows or pasture, wetlands and on roadsides, often in heavy soil. It prefers moist, fertile soils (Csurhes & Edwards 1998).

Flower colour:White
Distribution map:

http://www.chah.gov.au/avh/index.jsp 

South Australia distribution map:

http://www.flora.sa.gov.au/cgi-bin/texhtml?form=speciesfacts&keyname=Oenanthe+pimpinelloides&submit=Search 

Impacts:

Water Dropwort is one of seventeen sleeper weeds identified by the Bureau of Rural Sciences (following consultation with the Australian Weeds Committee) which could have nationally significant impacts on agriculture if allowed to spread.

In early 2006, Water Dropwort was reported as being limited to one infestation of about 35 hectares (nett area) or 84.2 hectares (gross area) in South Australia (where it was impacting on crops and pastures) and a second site of less than one hectare in Victoria (Cunningham & Brown 2006; Cunningham et al. 2006).

Water Dropwort has the potential to invade pastures and replace preferred gazing species (Cunningham & Brown 2006). It could also impact on natural ecosystems by outcompeting native plants (Kodela 2007, pers. comm.).

Cropping, grazing and horticulture are the land uses potentially at risk from spread of this species in its potential climatic range in southern temperate Australia (CSIRO 2002, in Cunningham & Brown 2006). The potential for Water Dropwort to invade pasture and forestry plantations, and its potential to grow in a range of Tasmanian environments, resulted in its listing as a declared weed for that State (DPIW 2007).

The roots are sometimes eaten overseas but caution is required because many species of Oenanthe are poisonous to stock and humans. However, there are no reports of livestock poisoning even though sheep graze on this species. (Cunningham et al. 2003). Water Dropwort has been reported as poisonous (Cooper & Johnson 1984). It contains the alleged 'psychotroph' myristicine (Duke & Ayensu 1985).

Origin:

Water Dropwort is native to western Europe and the Mediterranean region from Morocco to the Middle East (Duretto 1999).

History:

The first naturalised record of Water Dropwort was in December 1971 from South Australia at a site near Meadows in the Mount Lofty Ranges. In 1981 it was reported as covering 8 hectares in the Finniss River catchment; by 1993 the infestation covered 200 hectares, spreading 17 km down the Meadows Creek, mainly confined to the Meadows Creek Mount Barker Council Area (Cunningham & Brown 2006). In Victoria, Water Dropwort was common in Shepparton State Forest in 1980, and a few plants were found near Wonthaggi in 1996 (Duretto 1999).

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This database is designed to provide information, including biological and ecological, on invasive plant species that are on a national weed list, or are legislated against in a state or territory. While reasonable efforts have been made to ensure the accuracy of the information, no guarantee is given, nor responsibility taken, by the Commonwealth for its accuracy, currency or completeness. The Commonwealth does not accept any responsibility for any loss or damage that may be occasioned directly or indirectly through the use of, or reliance on, the information contained in this database. The information contained in this database does not necessarily represent the views of the Commonwealth. This database is not intended to be a complete source of information on the matters it deals with. For further information on the images contained in the database please contact the copyright owner. All images in the weed identification tool are managed by the Australian Plant Image Index (APII). Various copyright conditions apply for these images. For further information on the copyright conditions of images contained in the database please contact the APII at: photo@anbg.gov.au.