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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)

infestation (Photo: Sheldon Navie)

habit (Photo: Sheldon Navie)

habit with young seed-heads (Photo: Sheldon Navie)

habit with mature seed-heads (Photo: Sheldon Navie)

tussock and leaves (Photo: Sheldon Navie)

close-up of stem and leaf (Photo: Sheldon Navie)

close-up of lower part of young seed-head, showing the spreading branches (Photo: Sheldon Navie)

close-up of upper part of seed-head (Photo: Sheldon Navie)

close-up of seed-head in flower (Photo: Sheldon Navie)

close-up of mature seed-head with seeds (Photo: Sheldon Navie)

close-up of mature flower spikelets and seeds (Photo: Sangita Shrestha)

Sporobolus natalensis

Scientific Name

Sporobolus natalensis (Steud.) Dur. & Schinz.

Synonyms

Sporobolus capensis (P.Beauv.) Kunth var. laxus Nees
Sporobolus indicus (L.) R. Br. var. laxus (Nees) Stapf
Vilfa natalensis Steud.

Family

Gramineae (South Australia)
Poaceae (Queensland, New South Wales, the ACT, Victoria, Tasmania, Western Australia and the Northern Territory)

Common Names

giant rat's tail grass, giant rats tail grass, giant rats-tail grass, giant ratstail grass, GRT, GRT grass

Origin

Native to central and southern Africa (i.e. Ethiopia, Kenya, Tanzania, Uganda, Cameroon, Zambia, Botswana, Namibia and South Africa).

Naturalised Distribution

This species is becoming widely distributed in the eastern parts of Australia. It is most commonly found in the coastal regions of southern Queensland and northern New South Wales. Scattered infestations also occur in the coastal districts of central and northern Queensland, near Sydney in New South Wales, and near Darwin in the Northern Territory.

Habitat

A weed of pastures, roadsides, disturbed sites, open woodlands, grasslands, parks, footpaths and lawns in sub-tropical, tropical and sometimes also warmer temperate regions.

Habit

An upright (i.e. erect) and long-lived (i.e. perennial) grass growing 60-170 cm tall, and forming large tussocks.

Distinguishing Features

Stems and Leaves

The flowering stems (i.e. culms) are relatively slender, but somewhat wiry.

The leaves are very thin (i.e. linear) with a leaf sheath, which partially encloses the stem, and a spreading leaf blade that may droop towards the ground. The leaf sheaths are hairless (i.e. glabrous) and the leaf blades (25-50 cm long and 2-4 mm wide) may be flat or somewhat rolled (i.e. convolute). The leaf blades are also hairless (i.e. glabrous) and have pointed tips (i.e. acuminate apices). Where the sheath meets the leaf blade there is a tiny membrane topped with a fringe of hairs up to 0.4 mm long (i.e. the ligule is a ciliated membrane).

Flowers and Fruit

The seed-heads are borne at the top of the flowering stems (i.e. culms) and are initially thin and elongated in appearance (i.e. spiciform), but become more open and droop slightly as they mature. These seed-heads (20-30 cm long and about 3 cm wide) have numerous relatively long (3-7 cm long) branches. Each of these branches bears numerous tiny, densely packed, elongated (i.e. lanceolate) or oval (i.e. elliptic) flower spikelets (1.6-2.3 mm long) almost to its base. The dark green or greyish-green flower spikelets (1.6-2.3 mm long) contain a single tiny flower (i.e. floret) inside two bracts (i.e. glumes). The lower bract (i.e. glume) is 0.5-0.8 mm long and the upper bract (i.e. glume) is 0.8-1.3 mm long (i.e. at least half the length of the flower spikelet). Flowering occurs during spring, summer and autumn (i.e. from October through to July).

The tiny seeds (i.e. grains or caryopses) turn yellowish-brown or reddish-brown in colour as they mature. These seeds (0.7-0.8 mm long and up to 0.6 mm wide) are oval (i.e. ellipsoid) or egg-shaped (i.e. obovoid) and separate from the remainder of the flower spikelet at maturity (i.e. the pale coloured old glumes remain on the seed-head).

Reproduction and Dispersal

This species produces large quantities of tiny seeds.

These seeds become somewhat sticky when wet, and may be spread after becoming attached to animals, clothing and vehicles. They may also be dispersed by water, in mud, and in contaminated agricultural produce (e.g. fodder and pasture seed lots).

Environmental Impact

Giant rat's tail grass (Sporobolus natalensis) is a significant environmental weed in Queensland and northern New South Wales, and was recently listed as a priority environmental weed in at least one Natural Resource Management region. It invades native grasslands, open woodlands, conservation reserves and wetland areas. When fully established in an area, it can form a grass monoculture, excluding native plants and reducing biodiversity of native groundcover species. This can also have an impact on native herbivores, which find the plants unpalatable.

Giant rat's tail grass (Sporobolus natalensis) is listed among among the exotic perennial grass species whose invasion of native plant communities in New South Wales has been listed as a "key threatening process". Along with Sporobolus pyramidalis, this species is ranked among the top 25 environmental weeds in south-eastern Queensland. It is also thought to pose a significant threat to rangeland biodiversity in central and northern Queensland, and heavy infestations may also increase fire intensity in sensitive environmental areas. The Giant rat's tail grasses (Sporobolus natalensis and Sporobolus pyramidalis) are already of concern in several conservation areas in Queensland.

Other Impacts

Giant rat's tail grass (Sporobolus natalensis) is a serious weed of pastures in the coastal districts of Queensland and northern New South Wales. It is of low palatability to livestock and can greatly reduce the productivity of agricultural land by completely displacing desirable pasture species. This reduction in productivity can be exhibited in reduced stocking capacities, longer periods of time to record adequate weight gains in beef cattle, and higher costs in milk production on dairy farms. The economic costs incurred in managing this species with herbicides are also quite high, and heavily infested areas have reduced land values. Mature leaf blades and stems are tough for animals to graze, and have been known to loosen the teeth of cattle and horses.

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

Giant rats-tail grass (Sporobolus natalensis ) is very similar to other introduced rats-tail grasses (Sporobolus spp.) including another species known as giant rats-tail grass (Sporobolus pyramidalis), Parramatta grass (Sporobolus africanus), giant Parramatta grass (Sporobolus fertilis ) and American rats-tail grass (Sporobolus jacquemontii ). It is also similar to some native species such as the slender rats-tail grasses (Sporobolus creber and Sporobolus elongatus). Distinguishing between these species is often very difficult and a specialist may need to be consulted, however the following is a guide to the differences that may be apparent: