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Acetosa vesicaria. By Mark Marathon (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
Acetosa vesicaria fruit. By Mark Marathon (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
Scientific Name
Acetosa vesicaria (L.) A. Love
Synonyms
Rumex clementii DominRumex roseus L. (misapplied)Rumex vesicarius L.
Family
Polygonaceae
Common Names
bladder dock, bladderdock, hops, native hops, pink dock, rosy dock, ruby dock, wild hops
Origin
Native to the desert and semi-arid areas of North Africa, south-western Asia and the Indian sub-continent. Possibly also native to some parts of southern Europe.
Cultivation
It is thought that this species was introduced into Australia along with camels, either deliberately for feed or accidentally in saddles or packing (i.e. the soft fruit was used for padding in camel saddles).
Because of its brightly coloured fruiting perianths, this species has also often been deliberately cultivated in gardens in the drier parts of the country. Large infestations can be quite spectacular when in fruit and they are often mistaken for 'wildflowers'. Such infestations can sometimes even be regarded as a tourist attraction (e.g. in the Flinders Ranges in South Australia), and this has also undoubtedly led to further cultivation and spread of this species in recent times.
Naturalised Distribution
Naturalised in many inland parts of the country, and particularly common in the semi-arid and arid of parts of central Australia. Widely naturalised in Western Australia, South Australia, Queensland, New South Wales and the Northern Territory.
Rosy dock (Acetosa vesicaria) is present in many parts of Queensland and New South Wales, but is most commonly found in the western areas of these states. It is common and widespread in the arid zone in Western Australia, from the Pilbara in the north down to the Nullarbor in the south, and is also less common in the wheatbelt in the inland parts of south-western Western Australia. In South Australia it is present everywhere but in the extreme south-east of the state, and it is common in the southern and central parts of the Northern Territory.
There have also been sporadic records of this species in the far north-western parts of Victoria (i.e. in the Mildura area). However, these are probably the result of deliberate plantings or only short-lived occurrences, and rosy dock (Acetosa vesicaria) has not been shown to persist in this state.
Habitat
Rosy dock (Acetosa vesicaria) is most commonly a weed of roadsides and railways and in disturbed areas (e.g. in gravel pits and on mine sites) in the semi-arid and arid parts of Australia, where it grows on sandy alluvial soils and gravelly ironstone soils. However, it is also found in natural grassland and open woodland habitats, along waterways in inland areas, and in drier coastal habitats (particularly in northern and north-western Western Australia).
Habit
An upright (i.e. erect or ascending) or sometimes spreading (i.e. decumbent) short-lived (i.e. annual) herbaceous plant with numerous stems usually growing 10-60 cm tall, but occasionally reaching up to 1 m in height.
Distinguishing Features
- a short-lived plant with numerous upright stems that are hollow and slightly fleshy.
- its slightly fleshy leaves are triangular, arrow-shaped or sometimes heart-shaped.
- its flowers are initially quite inconspicuous and borne in upright branched clusters at the tips of the stems.
- its very conspicuous immature fruit are inflated or bladdery in nature and range from pink to bright red or purplish in colour.
- its mature fruit are papery and pale brown or dark brown in colour.
Seedling
Stems and Leaves
Numerous stems are usually produced from near the base of the plant, but these stems are only occasionally branched towards the top of the plant. They are relatively thick and stout, hollow, hairless (i.e. glabrous) and somewhat fleshy in nature (i.e. semi-succulent).
The alternately arranged leaves (2-10 cm long and 2-8 cm wide) are either triangular (i.e. with a truncate base), arrow-head shaped (i.e. with a sagittate base) or heart-shaped (i.e. with a cordate base) in outline. They are usually slightly thick and fleshy in nature (i.e. semi-succulent) and hairless (i.e. glabrous). The tips of the leaves are either rounded or pointed (i.e. apices are obtuse to sub-acute) and their margins are entire and somewhat wavy (i.e. undulate). These leaves are borne on stalks (i.e. petioles) that are almost as long as the leaf blades themselves (i.e. 2-10 cm long). However, the lowermost leaves tend to be larger and have longer leaf stalks and the uppermost leaves tend to be smaller and have shorter leaf stalks. The base of each leaf stalk (i.e. petiole) has dilated margins that form a see-through membranous sheath called an 'ochrea' which usually encloses part of the stem.
Flowers and Fruit
The flowers are borne in upright (i.e. erect) branched clusters at the tips of the stems (i.e. in terminal panicles). They are initially inconspicuous and greenish in colour. Each flower has three tiny 'sepals' and three 'petals' (i.e. inner and outer perianth segments). They also usually have six tiny stamens and three styles bearing very elongated stigmas. The outer perianth segments remain small and membranous as the fruit develops, while the inner perianth segments become inflated and enclose the fruit (they are then called valves). These flowers are borne on stalks (i.e. pedicels) 5-6 mm long that have a joint near their bases (i.e. they are articulated). In fact, there are usually two (or occasionally three) of these flowers clustered closely together at the top of each flower stalk (i.e. pedicel), with one (or two) of them hidden under one of the perianth segments of the other flower. Flowering usually occurs during late winter and spring (i.e. from July to September), but may be earlier in the southern parts of the country and later in northern regions.
The fruit is a small three-sided nut surrounded by three papery segments (i.e. valves). These valves are initially small and greenish in colour but become inflated and turn pinkish, bright pink, reddish-pink, bright red or purplish in colour as the fruit begins to mature. They are quite showy (12-25 mm long and about 15 mm wide), have a bladder-like appearance, and are prominently veined. These fruit eventually turn pale brown or dark brown in colour when fully mature and are then shed from the plant. Two main types of seeds have been found in plants in Australia, and these have been termed 'dark seeds' and 'light seeds'. Light seeds are paler in colour, larger and located at the centre of the fruit (i.e. there is usually only one of these seeds per fruit). Dark seeds are smaller, vary in colour from brown to greyish-brown to black, and are found within the periphery of the fruiting perianth (i.e. there may be 1-5 of these seeds per fruit).
Reproduction and Dispersal
This species reproduces entirely by seed, which are known to form a persistent seed bank.
It is commonly spread by human activities (i.e. on vehicles and machinery, particularly during mining operations) and the light papery fruit are well suited to wind and water dispersal. It is also spread around by people collecting the fruit and deliberately growing plants in gardens. This species is thought to be an important part of the diet of wild camels in central Australia, and it may also be dispersed by these feral and other animals (e.g. goats). One rosy dock (Acetosa vesicaria) control project noted that the spread of this species rapidly declined when cattle were restricted from accessing infested and clean sites, hence livestock may also play an important role in its dispersal in some areas.
Environmental Impact
Rosy dock (Acetosa vesicaria) is regarded as a significant environmental weed in the Northern Territory, and it is also an important environmental weed in many parts of Western Australia and South Australia. As this species is of most concern in the largely isolated parts of inland Australia, its significance as an environmental weed is probably underestimated in many cases. Rosy dock (Acetosa vesicaria) is a common and widespread invasive weed throughout the arid parts of Australia, where it tends to become dominant and out-compete native species. This leads to a reduction in the natural biodiversity of these areas and can eventually even damage ecosystem function.
In Western Australia, rosy dock (Acetosa vesicaria) infestations extend across a large area of the rangelands, and it is a weed in both undisturbed and degraded ecosystems. It is a major concern on numerous mine-sites in the semi-arid regions of Western Australia and the Northern Territory, many of which are located near national parks and reserves. It is generally introduced to these mine-sites on machinery and vehicles and takes hold in frequently disturbed areas. It often also becomes dominant in newly established rehabilitation areas, and can threaten the success of these rehabilitation efforts. Therefore, it is now actively controlled in rehabilitation and disturbed areas on many mining leases and is sometimes even the primary focus in mine-site weed control programs (e.g. at the Marandoo, Channar and Brockman mines in Hamersley Iron’s mining operations located in north-western Western Australia).
The Karijini National Park, also located in the Hamersley Ranges in north-western Western Australia, has a widespread infestation of this species which is said to represent a major threat to the natural values of the park. Because of these issues, coastal managers have placed rosy dock (Acetosa vesicaria) among the top ten environmental weeds of the coastal regions of northern Western Australia (i.e. in the Kimberley, Pilbara and Gascoyne regions).
In the southern parts of the Northern Territory, rosy dock (Acetosa vesicaria) is considered to be a problem weed in seasonal river systems, which are dry for most of the year. It is also present in disturbed areas in and near national parks (e.g. beside the MacDonnell Range National Park near Alice Springs) and is being actively managed in these areas in order to prevent its spread.
In South Australia it is present in several arid-zone national parks (i.e. in the Flinders Ranges National Park, Gammon Ranges National Park and Sandy Creek Conservation Park). In fact, it is such a problem in the Flinders Ranges region that its colourful fruiting displays have lured visitors to this area for more than fifty years. Management of this species, including the removal of grazing animals and control of the feral goat population, has largely removed it from the Arkaroola Wilderness Sanctuary in the northern Flinders Ranges.
Rosy dock (Acetosa vesicaria) has also invaded parks and reserves in western New South Wales. It is said to be widespread across the Kinchega National Park, south-east of Broken Hill, after favourable rains. Field surveys have also indicated that it occurs frequently in the Willyama Common, a reserve near the city of Broken Hill.
This environmental weed has even inspired an educational children's book, entitled The Story of Rosy Dock, that deals with conservation issues and describes the spread of this introduced plant from a garden to a position where it dominates the landscape.
Other Impacts
In addition to its adverse effects as an environmental weed, rosy dock (Acetosa vesicaria) is commonly found in rangeland pastures. It often replaces more desirable species in these areas, reducing the productivity of heavily invaded pastures. Though it is grazed to some degree, and may therefore be a source of feed, significant consumption by livestock can also cause oxalate and nitrate poisoning.
Legislation
Rosy dock (Acetosa vesicaria) is not declared or considered noxious by any state or territory government in Australia.
Similar Species
Rosy dock (Acetosa vesicaria) is usually easily distinguished by its brightly coloured bladdery fruit. However, closely related weeds such as rambling dock (Acetosa sagittata), curled dock (Rumex crispus) and clustered dock (Rumex conglomeratus) are reasonably similar. These species may be distinguished by the following differences:
- rosy dock (Acetosa vesicaria) is an upright (i.e. erect) plant with slightly fleshy, arrowhead-shaped (i.e. sagittate) or heart-shaped (i.e. cordate) leaves that have wavy (i.e. undulating) margins. Its flowers are initially greenish in colour and are borne in large branched clusters at the tips of the stems (i.e. in terminal leafless panicles). These flowers turn bright pink or red in colour and become inflated as the relatively large fruit (12-25 mm long) mature. It is a short-lived (i.e. annual) plant with hollow stems and does not produce underground tubers.
- rambling dock (Acetosa sagittata) is a scrambling or climbing plant with slightly fleshy, arrowhead-shaped (i.e. sagittate) leaves that have wavy (i.e. undulating) or slightly curled (i.e. crisped) margins. Its flowers are initially greenish in colour and are borne in large branched clusters at the tips of the stems (i.e. in terminal leafless panicles). These flowers turn pinkish or reddish in colour and become papery as the moderately large fruit (4-10 mm long) mature. It is a long-lived (i.e. perennial) plant with solid stems that produces underground tubers.
- curled dock (Rumex crispus) is an upright (i.e. erect) plant with somewhat elongated (i.e. lanceolate) leaves that have very curled (i.e. crisped) margins. Its flowers are initially greenish in colour and are borne in large branched clusters at the tips of the stems (i.e. in terminal leafless panicles). These flowers turn orange or reddish-brown in colour as the relatively small fruit (3-6 mm long) mature. It is a long-lived (i.e. perennial) plant with solid stems that does not produce underground tubers.
- clustered dock (Rumex conglomeratus) is an upright (i.e. erect) plant with egg-shaped (i.e. ovate) to somewhat elongated (i.e. lanceolate) leaves that have wavy (i.e. undulating) or curled (i.e. crisped) margins. Its flowers are initially greenish in colour and are borne in large branched leafy clusters at the tips of the stems (i.e. in terminal leafy panicles). These flowers turn orange or reddish-brown in colour as the relatively small fruit (2-3 mm long) mature. It is a long-lived (i.e. perennial) plant with solid stems that does not produce underground tubers.
In addition, there is a group of native plants called hopbushes (Dodonaea spp.) that have similar reddish, three-winged, bladdery fruit and also mainly grow in inland areas. However, these species can be easily distinguished from rosy dock (Acetosa vesicaria) by their solid woody stems and by their long-lived (i.e. perennial) shrubby habit (i.e. usually growing 1-4 m tall).
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