giant rat's tail grass

Sporobolous natalensis
Grass
Alternate
Simple
Green
Green

An upright and long-lived grass growing 60-170 cm tall and forming large tussocks. Its very long and narrow leaf blades (20-50 cm long and 2-4 mm wide) may be flat or somewhat rolledits elongated seed-heads (20-30 cm long and about 3 cm wide) have many branches. These seed-head branches are initially held closely to the stem, but become more open and slightly drooping as they mature. Each of these branches bears numerous tiny flower spikelets (1.5-2 mm long).

Common names 
Also known as: giant rat's tail grass, GRT grass, GRT ,
Family 
Poaceae
Deciduous 
No
Flowering time 
Spring- Autumn
Native/Exotic 
Exotic
Origin 
Native to central and southern Africa (i.e. Ethiopia, Kenya, Tanzania, Uganda, Cameroon, Zambia, Botswana, Namibia and South Africa).
Notifiable 
No
State declaration 
Class 2
Council declaration 
Class R – Reduce populations
Known 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.

Impact and control methods 

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.

Stem 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 fruits 

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).

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: giant rats-tail grass (Sporobolus natalensis) is a relatively large plant (60-150 cm tall) with relatively large spike-like (i.e. spiciform) seed-heads (20-30 cm long). These seed-heads have numerous relatively long branches (30-70 mm long) that usually spread away from the main stem. These branches are normally densely arranged and the seed-head is un-interrupted. Its flower spikelets are moderately-sized (1.6-2.3 mm long).giant rats-tail grass (Sporobolus pyramidalis) is a relatively large plant (usually 90-200 cm tall) with relatively large pyramid-shaped (i.e. pyramidal) seed-heads (20-45 cm long). These seed-heads have numerous relatively long branches (50-100 mm long) that stiffly spread away from the main stem. Its flower spikelets are moderately-sized (1.7-2.2 mm long).Parramatta grass (Sporobolus africanus) is a relatively small plant (usually less than 50 cm tall) with relatively small spike-like (i.e. spiciform) seed-heads (6-35 cm long). These seed-heads have numerous short branches (10-20 mm long) that are usually held closely (i.e. appressed) to the main stem. These branches are normally densely arranged and the seed-head is mostly un-interrupted (except occasionally at the base). Its flower spikelets are relatively large (2-2.8 mm long).giant Parramatta grass (Sporobolus fertilis) is a relatively large plant (usually 80-160 cm tall) with relatively large spike-like (i.e. spiciform) seed-heads (15-50 cm long). These seed-heads have numerous moderately long branches (20-80 mm long) that are held closely (i.e. appressed) to the main stem or slightly spreading. These branches are normally densely arranged and the seed-head is mostly un-interrupted (except occasionally at the base). Its flower spikelets are relatively small (1.5-2 mm long).American rats-tail grass (Sporobolus jacquemontii) is a moderately-sized plant (usually 50-75 cm tall) with relatively small elongated seed-heads (8-25 cm long). These seed-heads have numerous relatively long branches (50-100 mm long) that usually spread away from the main stem. These branches are normally densely arranged and the seed-head is un-interrupted. Its flower spikelets are relatively small (1.5-2 mm long).slender rats-tail grass (Sporobolus creber) is a moderately-sized plant (usually less than 100 cm tall) with relatively long and very narrow spike-like (i.e. spiciform) seed-heads (18-60 cm long). These seed-heads have numerous short stiff branches (5-10 mm long) that are always held closely (i.e. appressed) to the main stem. These branches are normally widely spaced and the seed-head is interrupted (except near the top). Its flower spikelets are relatively small (1.2-1.7 mm long).slender rats-tail grass (Sporobolus elongatus) is a moderately-sized plant (usually 50-100 cm tall) with relatively long and narrow spike-like (i.e. spiciform) seed-heads (10-30 cm long). These seed-heads have numerous relatively long branches (40-80 mm long) that are usually held closely (i.e. appressed) to the main stem (sometimes slightly spreading). These branches are normally densely arranged and the seed-head is mostly un-interrupted (except occasionally at the base). Its flower spikelets are moderately-sized (1.5-2.3 mm long).