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Scientific Name
Synonyms
Family
Common Names
Origin
Naturalised Distribution
Habitat
Habit
Distinguishing Features
Stems and Leaves
Flowers and Fruit
Reproduction and Dispersal
Environmental Impact
Other Impacts
Legislation
Management
Similar Species
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Click on images to enlarge

infestation (Photo: Sheldon Navie)

habit (Photo: Sheldon Navie)

habit (Photo: Sheldon Navie)

close-up of stems and leaves (Photo: Sheldon Navie)

the tip of a flowering stem, which tapers into a very sharp spine (Photo: Sheldon Navie)

flower buds (Photo: Sheldon Navie)

flowers (Photo: Jackie Miles and Max Campbell)

immature fruit (Photo: Sheldon Navie)

close-up of mature fruit (Photo: Sheldon Navie)

sea rush, Juncus kraussii subsp. australiensis (Photo: Sheldon Navie)

Juncus acutus subsp. acutus

Scientific Name

Juncus acutus L. subsp. acutus

Synonyms

Juncus acutus L.

Family

Juncaceae

Common Names

cultivation rush, sharp pointed rush, sharp rush, sharp-pointed rush, spiny rush, sharp sea rush

Origin

The exact origin of this species is obscure, but this subspecies is thought to be native to the Mediterranean region and western Europe.

Naturalised Distribution

Widely naturalised in southern Australia. It is common and widespread in eastern and southern New South Wales, the ACT, Victoria, south-eastern South Australia and south-western Western Australia. Occasionally naturalised in other parts of South Australia, in Tasmania and in the southern parts of the Northern Territory. It has also recently become sparingly naturalised in south-eastern Queensland.

Habitat

A weed of moist habitats in temperate regions, including pastures, waterways, swamps, marshes, wetland areas, disturbed sites, waste areas and coastal environs.

Habit

An upright (i.e. erect) and long-lived (i.e. perennial) plant that is grass-like in appearance and eventually forms large tussocks. It usually grows 1-1.2 m tall, but may occasionally reach up to 2 m in height.

Distinguishing Features

Stems and Leaves

The numerous upright (i.e. erect) stems are produced off very short creeping underground stems (i.e. rhizomes). These upright stems (2-5 mm diameter) are unbranched, rounded in cross-section (i.e. cylindrical) and hairless (i.e. glabrous). They bear a dense cluster of flowers just below their tips, which taper into a very sharp spine.

The leaves are very similar in appearance to the stems, except that they do not bear flowers near their tips. They are also produced from the short creeping underground stems (i.e. rhizomes) at the base of the plant.

Flowers and Fruit

The flowers are either greenish, brown or reddish-brown in colour depending on their age. They are borne in dense branching clusters about 4-13 cm long and 3 cm wide. These clusters are made up of 5-50 smaller clusters, each containing 1-6 flowers. At the base of these flowers clusters there are usually one or two leafy bracts (4-25 cm long). Individual flowers are inconspicuous and almost stalkless (i.e. sessile or sub-sessile). They consist of three 'sepals' (i.e. outer tepals) and three 'petals' (i.e. inner tepals). These tepals are small (2-4 mm long) and often have narrow whitish margins near their tips. The flowers also have six small stamens and a three-celled ovary. Flowering occurs throughout the year, but mostly during spring and summer.

The fruit is a yellowish-brown to chestnut-brown capsule (5-6 mm long) that is egg-shaped (i.e. ovoid) but with a pointed tip (i.e. acute apex). Each capsule contains many oval (i.e. ellipsoid) or irregularly shaped seeds (1.2-2 mm long). These seeds are brown in colour and have a membranous tail at either end.

Reproduction and Dispersal

This species reproduces mostly by seed, but also spreads vegetatively via the short, creeping, underground stems (i.e. rhizomes).

Seeds are dispersed in mud and contaminated agricultural produce and also by water, vehicles and machinery. The rhizomes may be spread during cultivation, road maintenance and other soil moving activities.

Environmental Impact

Spiny rush (Juncus acutus subsp. acutus) is regarded as a very serious environmental weed in Victoria and New South Wales, an environmental weed of some importance in South australia and Western Australia, and as a minor or potential environmental weed in southern Queensland and the southern parts of the Northern Territory. It was recently listed as a priority environmental weed in two Natural Resource Management regions.

Other Impacts

This species can eliminate all useful pasture species in infested areas, and as it is not readily eaten by grazing animals, it may significantly reduce the productivity of pastures. Because of its sharp spines, stands of spiny rush (Juncus acutus subsp. acutus) can also become impenetrable to livestock and humans, preventing access to water. The sharp spines, can also cause injury to animals, livestock and humans.

Infestations can provide habitat for smaller pest animals, and when growing in drains and channels spiny rush (Juncus acutus subsp. acutus) can seriously obstruct water flow, causing flooding.

Legislation

This species is declared under legislation in the following states and territories:

Management

For information on the management of this species see the following resources:

Similar Species

Spiny rush (Juncus acutus subsp. acutus) is very similar to the native sea rush (Juncus kraussii subsp. australiensis). These two species can be distinguished by the following differences:

Spiny rush (Juncus acutus subsp. acutus) is also similar to many other rushes (Juncus spp.) and also some sedges (Cyperus spp. and Carex spp.). There are too many species to mention, however spiny rush (Juncus acutus subsp. acutus) can usually be distinguished from these by its very sharply pointed stems and leaves.