Quick Facts

Quick facts

• Originally from western Europe, the Mediterranean region to the Middle East, Water Dropwort (Oenanthe pimpinelloides) is an invasive perennial erect herb.
• Plants are 0.3–1 metre tall, with parsley-like or fennel-like foliage, and umbrella-like clusters of small white flowers.
• Plant produce rosettes in spring, elongating and flowering and fruiting in summer, dying back to ground level in winter, regrowing the following season.
• Found in cool temperate areas in seasonal damp to wet open areas and pastures, displacing desirable species. 
• Livestock do graze this species but favour other pasture species, and it has been reported to be poisonous in large quantities.
• Reproduction is via seed and root tubers. Seeds are float on water, and are further spreads by stock, hay and machinery. Root tubers also spread along watercourses and as a contaminant of hay.
• There is good potential for eradicating or controlling this species.

What Does It Look Like?

What is it?

Water Dropwort (Oenanthe pimpinelloides) is an erect perennial herb growing 30-100 cm high. Plant produce basal rosettes in spring, followed by a solid, striated stem that branches. Roots have rounded tubers towards their ends. There are two types of leaves; the basal rosette 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 inflorescence (flowering head) is a white flowering compound umbel (numerous umbrella-shaped flower clusters). The umbel-shaped flower-heads are at the end of the stems, 20–50 mm in diameter, with a peduncle or main stalk 40-120 mm 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 spiny 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.

Flower colour

White

Growth form (weed type/habit)

Herb

Where it currently grows? Preferred habitat

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

Are there similar species?

Water Dropwort is superficially similar to other, more common, Parsley or Fennel-like species in the Apiaceae or 'Carrot' family that are naturalised in Australia. Extreme caution should be taken not to confuse Water Dropwort with the very poisonous Cowbane (Cicuta virosa), Hemlock (Conium maculatum) or Hemlock Water Dropwort (Oenanthe crocata) (Shepherd 2004). Water Dropwort may be confused with yarrow Achillea millefolium (identified by large, feathery leaves).

Why Is It A Weed?

What are its impacts?

Water Dropwort (Oenanthe pimpinelloides) 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.

Agriculture:  Water Dropwort appears to replace pasture species and competes with native species during summer (Government of South Australia 2014). Cunningham & Brown (2006) also report that Water Dropwort has the potential to invade pastures and replace preferred gazing species.  In South Australia in early 2006, Water Dropwort was reported as being limited to one infestation of about 35 hectares (net area) or 84.2 hectares (gross area) where it was impacting on crops and pastures, and at a second site of less than one hectare in Victoria (Cunningham & Brown 2006; Cunningham et al. 2006). 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 (DPIPWE Tasmania 2019). 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). However, livestock do not usually graze on it, and it has been reported to be poisonous (Government of South Australia 2014).

Native ecosystems: It could also impact on natural ecosystems by out-competing native plants (Kodela 2007, pers. comm.).

Urban areas:  Not known from urban areas, but may be able invade ephemeral riparian areas in urban environments.

How does it spread?

Water Dropwort primary means of spread is by seed, but it is also spread vegetatively by root tubers. Seeds are spread by floating away on water and other means of seed-spread  include wind, stock, hay and machinery. Tubers may also be a means of spread via water along watercourses and as a contaminant of hay.

What is its history in Australia?

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).

First collected from northern Tasmania in 2013 from Meander River south–west of Hadspen, on a flood plain at edge of cropped paddock (AVH 2021).

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How To Manage It?

Best practice management

Water Dropwort has been classed as a Category 2 Sleeper Weed recommended for immediate eradication since recent field surveys had been completed (Cunningham & Brown 2006). The feasibility of eradicating the Australian infestations is discussed by Woldendorp & Bomford (2004) and Cunningham & Brown (2006). Larger infestations require an integrated management strategy that could involve herbicide application and the establishment of competitive species as effective control measures (Cooke pers. comm., in Cunningham & Brown 2006). Eradication will also be assisted through awareness programs to recognise and control this weed. Preventing further spread of this weed is the best way of limiting its spread and controlling populations

Chemical control: Herbicides that target other broad leaf species could be effective in controlling Water Dropwort, however, care should be taken around water ways or wetlands as these herbicides could be harmful to useful pasture species and are sometimes unsuitable for use around watercourses. Always read and follow the product label. A range of herbicide treatments at the stem elongation stage in spring before autumn sowing of pastures provides effective short-term control with a reduction in Water Dropwort abundance for up to 18 months after sowing of pasture (Mitchell et al. 1995).

Please see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au 

Non-chemical control: Physical control: Smaller infestations could be removed by hand.

Competition and management: Water Dropwort is grazed by cattle (Groves & Hosking 1998), which could be part of a control plan. As Water Dropwort has been found to regenerate from seed more densely in unsown plots than in plots of established perennial pasture, so upgrading pastures may be a strategy to reduce the rate of spread by seed. Competition from perennial grasses such as Phalaris and broad-leaved species like white or subterranean clover, reduces seedling survival, therefore maintaining a dense pasture is an effective management strategy. Effective grazing by sheep in winter improves density through tillering of the Phalaris and clover, but cattle may bare the ground by pugging, giving Water Dropwort seedlings sites to establish (Government of South Australia 2014).

Does it have a biological control agent?

NO

When does it grow? (lifecycle/growth calendar)

Water Dropwort is a perennial. It flowers from October to December (Duretto 1999).

Where Is It Found?

Which states and territories is it found?

VIC, SA TAS

What areas within states and territories is it found?

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).

In Tasmania by Meander River south west of Hadspen Water Dropwort has been found in northern part of the Island, in water courses on the edge of a flood plain at edge of cropped paddock

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).

Where does it originate?

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

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

NO

Where is it a declared weed?

SA, TAS, VIC

Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?

NO

Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?

YES

Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Oenanthe pimpinelloides

Other scientific names (synonyms)?

Oenantha pimpinelloides Jessop (incorrect spelling)

Does it have other known common name(s)?

Meadow Parsley, Corky Fruit, Corky-fruited Water Dropwort