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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 mature seed-heads (Photo: Sheldon Navie)

tussock and leaves (Photo: Sheldon Navie)

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

younger seed-head (Photo: Sheldon Navie)

mature seed-head with stiffly spreading branches (Photo: Sheldon Navie)

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

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

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

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

Sporobolus pyramidalis

Scientific Name

Sporobolus pyramidalis Beauv.

Synonyms

Sporobolus indicus (L.) R. Br. var. pyramidalis (Beauv.) Veldkamp

Family

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

Common Names

cat's tail dropseed, cat's tailgrass, giant rat's tail grass, giant rats tail grass, giant rats-tail grass, giant ratstail grass, GRT, GRT grass, Parramatta grass, West Indies smutgrass, whorled dropseed

Origin

Native to sub-Saharan Africa, Madagascar, Mauritius and parts of the the Arabian Peninsula (i.e. Yemen).

Naturalised Distribution

This species is widely distributed in the eastern parts of Australia. It is most common in the coastal districts of southern Queensland and northern New South Wales. Also relatively common in the coastal districts of central and northern Queensland and recorded from a few locations 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 90-200 cm tall, that forms large dense tussocks.

Distinguishing Features

Stems and Leaves

The flowering stems (i.e. culms) are 2-5 mm thick and somewhat wiry.

The leaves are very elongated (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), or have some tiny hairs along their margins, and the leaf blades may be flat or somewhat rolled (i.e. convolute). These leaf blades (20-70 cm long and 3-10 mm wide) are hairless (i.e. glabrous), or have some tiny hairs along their margins, and have pointed tips (i.e. acuminate apices). Where the sheath meets the leaf blade there is a fringe of tiny hairs or a very short membrane (0.2-0.3 mm long) topped with tiny hairs (i.e. the ligule is ciliate or a ciliated membrane).

Flowers and Fruit

The elongated seed-heads are borne at the top of the stems and are initially thin in nature (i.e. spiciform), but become more open and narrowly pyramid-shaped (i.e. pyramidal) as they mature. These seed-heads (20-45 cm long) have numerous stiffly spreading branches (5-10 cm long). Each of these branches bears numerous tiny, densely packed, and elongated (i.e. lanceolate) or oval (i.e. elliptic) flower spikelets almost to its base. The dark green or greyish-green flower spikelets (1.7-2.2 mm long) contain a single tiny flower (i.e. floret) inside two bracts (i.e. glumes). The lower bract (i.e. glume) is 0.3-0.5 mm long and the upper bract (i.e. glume) is 0.5-0.8 mm long (i.e. less than half the length of the flower spikelet). Flowering occurs throughout the year, but mainly during spring, summer and autumn.

The tiny seeds (i.e. grains or caryopses) turn yellowish-brown or reddish-brown in colour as they mature. These seeds (0.8-1 mm long and up to 0.5 mm wide) are oblong 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 pyramidalis) is a significant environmental weed in Queensland and northern New South Wales. It was also recently listed as a priority environmental weed in at least one Natural Resource Management region. This species 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.

Along with Sporobolus natalensis, 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 pyramidalis) 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 pyramidalis ) is very similar to other introduced rats-tail grasses (Sporobolus spp.) including another species known as giant rats-tail grass (Sporobolus natalensis), 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: