Quick Facts

Quick facts

• Giant Reed (Arundo donax) is a large perennial grass growing to 6–7 meters in height.
• It commonly occurs as a weed in and around urbanised areas in temperate, sub-tropical and tropical regions, and is found growing in moist areas such as stream and river banks, drainage lines, swamp areas and urban bushland.
• It is an aggressive, fast growing weed that can form large dense stands that displace native plant and animal species.
• Once established it is difficult to remove as resprouting occurs from extensive underground stems (rhizomes).
• Small infestations can be removed by hand but any rhizome (underground stem) remaining will regrow.
• Herbicides are effective in killing the whole plant if applied while actively growing.

What Does It Look Like?

What is it?

Giant Reed (Arundo donax) is a large perennial grass growing in clumps up to 6–7  m in height, sparingly branched, or single stemmed. The above-ground stems are large and somewhat 'woody', often more than 1–2  cm in diameter, and arise from a rhizomes (A thick, scaly underground stems). The leaves are sheathed (initially wrapped around the stem, and leaf blades (leaves not wrapped around the stem) are very long up to 1 metre  long and 1–8  cm wide, lanceolate (lance-shaped) or elongated (linear), pointed at the tip, and hairless on both sides. A ligule (small protrusion at the base of a leaf) occurs where the leaf blade meets the stem, which consists of a short membranous flap topped with short hairs 1.5–3 mm long.

The erect flower-heads (inflorescences) are plume-like loosely spreading and fluffy, 30–70 cm long. The inflorescence itself is light brown in colour, but becomes whitish as it matures. The individual spikelets are 10-14 mm long, and bear long silky, whitish hairs 8-10 mm long. Each spikelet contains 3-5 flowers (florets) with 2 subequal glumes which break up as the structure matures (Starr et al. 2003; Navie 2004; Linder 2005).

No viable or mature fruit (or seed) is produced. 

For further information and assistance with identification of Giant Reed, contact the herbarium in your state or territory.

Flower colour

White

Growth form (weed type/habit)

Grass

Where it currently grows? Preferred habitat

Giant Reed, as a garden escapee, commonly becomes naturalised in or near populated areas. It occurs mainly in moist areas, growing along lakes, stream and river banks, swamp areas, roadsides and urban bushland, generally in subtropical and tropical regions. It occasionally occurs in wetter inland regions of Australia (Navie 2004; Linder 2005), in ephemeral sandy creeks in arid and semi-arid areas.

Are there similar species?

Giant Reed (Arundo donax) can be confused with the Common Reed (Phragmites australis) and Elephant Grass (Cenchrus purpureus).

Compared to Common Reed (Phragmites australis), Giant Reed is generally a taller plant 2–7 m tall, with wider leaves 2–8 cm. 

Common Reed is notably smaller 1.5–3 m tall with relatively narrow leaves 1–3.5 cm. The inflorescence of Giant Reed is typically white when mature, while that of Common Reed is generally light brown (Navie 2004).

Compared to Elephant Grass (Cenchrus purpureus) [as Pennisetum purpureum], Giant Reed has wider leaves 2–8 cm. The leaves of Elephant Grass are relatively narrow 2–4 cm). The inflorescence of Giant Reed is much branched and feathery, while that of Elephant grass is spike-like and bristly (Navie 2004).

Why Is It A Weed?

What are its impacts?

Agricultural: Mainly grows in riparian areas and can form dense infestations preventing animals movement and access to water ways in rangelands.  The stems and leaves contain alkaloids, tryptamines and other toxins that make them inedible to most herbivorous insects and also deter grazing animals (Government of South Australia 2021). 

Native ecosystems: Giant Reed can be aggressive as an invasive plant and can out-compete and displace native plant and animal species due to the formation of dense monocultures and extensive clonal root systems in riparian or damp areas, especially in ephemeral creeks in semi-arid to arid areas.  If Giant Reed becomes abundant, it can alter riparian areas from flood-defined to fire-defined natural communities (Bell 1997). The removal of native plant species can negatively impact on native fauna, particularly birds, which often require habitat and food resources provided by native plants. All evidence suggests that Giant Reed provides neither habitat nor food to native wildlife due to toxins in the pants deterring animals. Large dense infestations can block and change stream flow causing flooding due to their bulk and ability to trap sediment and floating debris. The dry stems and dry leaves are highly flammable, increasing fire risk and intensity in riparian vegetation. The dense stands of Giant Reed can resprout quickly after burning (Bell 1997). It can therefore quickly replace native vegetation after fires, and can present a fire hazard in native and urban areas (Dudley 1998, PIER 2007). Giant Reed also provided little shading over in-stream habitats, resulting in increased water temperatures that may impact on aquatic flora and fauna (Bell 1997; Dudley 1998). Giant Reed is also suspected of releasing toxins into the water which deter other plants and favor its own growth. Toxins in the plant itself make it unpalatable to native fauna (Bell 1997; Dudley 1998; CRC 2005).

Urban areas: Can be found in urban areas and can escape, impact, and spread if grow along river banks, wetlands, roadsides and wastelands, It has been cultivated in parks and gardens, but most plants are remnant or weedy populations in cities and towns. Due to its height, it has been known, to interfere with and short-circuit power lines, causing fires (Armstrong & Breaden 2007).

How does it spread?

Giant Reed can spread slowly by the growth of underground stems (rhizomes), which sprout new above-ground stems. Dispersal of small pieces of the rhizomes can occur due to contamination of dumped garden waste or soil (Navie 2004) or, if occurring in riparian habitats, they can be carried downstream during flooding events (Bell 1997). Even small fragments of rhizome can readily sprout (Starr et al. 2003). Fresh stems have been observed to produce roots from the nodes if in contact with soil (Dudley 1998). This species does produce seed, which are wind or water dispersed, but in many areas where it occurs these are rarely viable (Dudley 1998).

What is its history in Australia?

Giant Reed was most likely introduced into Australia as a garden plant, and most infestations are probably due to garden escapes (Navie 2004). The time of introduction is uncertain. In some areas it was introduced for erosion control (Bell 1997; Armstrong & Breaden 2007).

How To Manage It?

Best practice management

Non-chemical control: Smaller infestations can be removed manually, but it is labour intensive as all underground rhizomes must be removed to prevent regeneration; however, manual removal is more selective and may be necessary to prevent damage to nearby native plants (Starr et al. 2003). Hand pulling can be effective on plants of less than 2 m in height, while larger plants can be removed using hand tools, especially in combination with cutting off stems near their base (Dudley 1998). Stems and roots should be removed and preferably burned on site to prevent further dispersal through disposal of the waste offsite. However, any rhizomes (underground stems) left in the ground will re-grow

Mechanical control: Larger monotypic stands can be mechanically removed by bulldozing or by tractor. This can be effective before the manual removal of underground rhizomes or chemical control (Starr et al. 2003; Armstrong & Breaden 2007).

Fire: Burning can be effective for the removal of above-ground vegetation, but is not recommended as it does not kill the rhizomes, and may favour the weed over native species during regeneration (Starr et al. 2003).

Chemical control: The most effective treatment of Giant Reed is to apply herbicides to the leaves immediately post flowering and before the plants become dormant in cooler months (i.e. when the plant is actively transporting nutrients to the roots), so the herbicide is effectively transported to the root mass (Bell 1997). Chemical control is also effectively applied when the above-ground vegetation has been cut. Stems must be treated immediately after cutting to ensure uptake of the herbicide (Bell 1997). Frequent follow-up applications are recommended over the following six months (Dudley 1998).

A combination of these control methods is also effective, where stems are cut to the ground and allowed to regrow for approximately six weeks, when herbicides are then applied. This will reduce the amount of chemical needed and allows it to be more evenly applied (Bell 1997). It should be noted, however, that the use of herbicides can be problematic near waterways (CRC 2005). 

Please see; Brisbane City Council 2021; DPI NSW (2019); Invasive Species Unit, Biosecurity SA (2018); the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au

Does it have a biological control agent?

NO

When does it grow? (lifecycle/growth calendar)

Giant Reed flowers in spring through to summer, but does not normally flower in Victoria (Richardson et al. 2006). Viable seed is not produced in Australia, and seed production is rarely observed in North America (Bell 1997). New shoots can arise from the rhizome in almost any season, but most commonly during spring, and during warmer months. It is very fast growing and has been observed to grow as quickly as 5 cm per day (Bell 1997). Complete die-back of the plant is rare, but the stems and leaves tend to brown during colder months, apparently becoming dormant (Dudley 1998).

Where Is It Found?

Which states and territories is it found?

NSW, NT, QLD, SA, TAS, VIC, WA

What areas within states and territories is it found?

Giant Reed is widespread in Australia, and occurs in all states and the Northern Territory. It is most common around major urban centres (Sydney, Brisbane, Perth, Melbourne, Adelaide), but it has a scattered distribution in each state (Navie 2004).

In New South Wales it mainly occurs along the central and northern coast (Navie 2004). 

In Western Australia it occurs most frequently near Perth, but also from Geraldton to Albany, and occasionally near inhabited regions in the Gascoyne, Pilbara and Kimberly regions (Hussey et al. 2007). 

In South Australia it is mainly centralised around Adelaide and the Yorke Peninsula in scattered in the Arid areas in ephemeral sandy creek beds. 

In Queensland it occurs mainly around Brisbane and is widespread along the eastern coast. 

It has also been recorded in Tasmania (AVH 2021; Navie 2004).

Where does it originate?

Giant Reed is native to Mediterranean areas in southern Europe and most of Asia (Navie 2004; Richardson et al. 2006). It is widely naturalised in warm-temperate and tropical areas (Starr et al. 1993), and occurs as a weed in Spain, Iran, Argentina, Chile, New Zealand, and southern and central North America (Armstrong & Breaden 2007; USDA 2007). It is a major threat to remnant riparian habitats, particularly in the United States (Bell 1997).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

NO

Where is it a declared weed?

SA

Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?

NO

Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?

NO

Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Arundo donax

Other scientific names (synonyms)?

• Arundo donax L. var. donax
• Arundo donax var. versicolor (Mill.) Stokes
• Arundo versicolor Mill.
• Phragmites australis (Cav.) Trin. ex Steud. (misapplied by Turner, J.S., Smithers, C.N. & Hoogland, R.D. 1968, The Conservation of Norfolk Island. 32.)

Does it have other known common name(s)?

Elephant Grass, Danubian Reed, Spanish Reed, Bamboo Reed, False Bamboo, Arundo, Wild Cane