Scientific name: Arundo donax L.
Common names: giant reed, giant cane
Family: Poaceae (Gramineae)
Risk Assessment score: 14 | Value obtained according to a protocol adapted from the Australian Weed Risk Assessment (Pheloung et al. 1999), by Morais et al. (2017), according to which values above 13 mean that the species has risk of having invasive behavior in the Portuguese territory | Updated on 30/09/2017.
Synonymy: Arundo maxima Forskål
Last update: 09/07/2021
How to recognise it
Flowering: August to October.
Common reed (Phragmites australis (Cav.) Trin. ex Steud.) is similar but is smaller (both in diameter, as in the culms’ height) and the rachilla presents long hairs.
Characteristics that aid invasion
It reproduces only vegetatively, by rhizome, with very high growth rates. The rhizomes regenerate vigorously after cutting, renewing and even enhancing the invasion problems.
The rhizome fragments are transported along watercourses and originate new, very distant, invasion foci when retained in the banks.
The dead branches are flammable and the plants regenerate after a fire.
Native distribution area
Distribution in Portugal
Mainland Portugal (all provinces); Azores archipelago (all islands); Madeira archipelago (islands of Madeira and Porto Santo).
Geographic areas where there are records of Arundo donax
Europe (Spain, France, Germany, Hungary, Malta), Africa (Namibia, Tanzania, South Africa), Australia, New Zealand, North America (Mexico, USA), South America (Venezuela, Peru, Argentina, Chile).
Probably due to the interest in the culms, namely for use in agriculture, hedges and to fixate slopes.
Preferential invasion environments
Close to watercourses, dykes, humid areas, wetlands and coastal swampy areas. It is also very frequent on roadsides and crop areas.
It is cultivated throughout the country, except in high altitudes.
Impacts on ecossystems
It clones itself until it occupies extensive areas, hampering the development of native vegetation (namely vegetation in riparian areas), barring the associated fauna and interfering with the water flow.
In islands/cliffs it hinders the nesting of some birds, with great impacts on those species.
High costs in the application of control methodologies.
In watercourses it constitutes a serious obstacle to flow, consequently enhancing the risk of floods and spates. In extreme situations, it may interfere with the movement of boats and cause damages in structures like bridges and dams.
Giant reed is very flammable, even when green, which accentuates the probability of fire occurrence and damages caused by it.
Natura 2000 Network habitats more subject to impacts
– Alluvial forests with Alnus glutinosa (91E0);
– Riparian mixed forests of Quercus robur, Ulmus minor and Fraxinus angustifolia along the great rivers (91F0);
– Salix alba and Populus alba galleries (92A0);
– Riparian formations on intermittent Mediterranean water courses with Rhododendron ponticum, Salix and others (92B0);
– Southern riparian galleries and thickets (Nerio-Tamaricetea e Securinegion tinctoriae) (92D0 pt1, pt2);
– Rivers with muddy banks with Chenopodium rubri p. p. and Bidention p. p. vegetation (3270);
– Constantly flowing Mediterranean rivers with Paspalo-Agrostidion species and hanging curtains of Salix alba and Populus alba (3280);
– Intermittently flowing Mediterranean rivers of the Paspalo-Agrostidion (3290).
Controlling an invasive species demands a well-planned management, which includes the determination of the invaded area, identifying the causes of invasion, assessing the impacts, defining the intervention priorities, selecting the adequate control methodologies and their application. Afterwards it is fundamental to monitor the efficiency of the methodologies and recuperation of the intervened area as to perform, whenever necessary, the follow-up control.
The control methodologies used for Arundo donax include:
Hand pulling: preferential methodology for young plants (with rhizomes of small dimensions), up to 2 m high. In more compacted substrates, hand pulling must be made during the rainy as to facilitate the removal of rhizomes. As much as possible, it should be guaranteed that there are no rhizomes and/or large rhizome fragments left in the ground because they regenerate very vigorously, diminishing the efficacy of this methodology.
Cutting and subsequent removal of rhizomes: applied to plants with large rhizomes. It may be done manually and/or with mechanical equipment. It should be guaranteed that there are no large rhizomes left in the ground. These rhizomes should be taken from the location and burned later. The stems should be also destroyed.
Physical + chemical control
Cut stump method: to be done on larger plants. Cut the stems as close to the ground possible and immediately apply herbicide (without fail in the following seconds) (active substance: glyphosate) to the cut surface. Some authors refer that the sprouts are more sensitive to the herbicide, so alternatively, the application of herbicide may be done when the sprouts are 1 to 2 m high. The application of herbicide should be made after flowering.
Foliar application of herbicide: applied on young sprouts, up to 1-2 m high. Spray with herbicide (active substance: glyphosate) limiting its application to the target species. It should be done after flowering, using sprayers.
Visit the webpage How to Control for additional and more detailed information about the correct application of these methodologies.
Benton N, Bell G, Swearingen JM (2005) Giant reed – Arundo donax. In: Plant Conservation Alliance’s Alien Plant Working Group. Weeds gone Wild: Alien Plant Invader of Natural Areas. Available: http://www.nps.gov/plants/alien/fact/ardo1.htm [Retrieved 10/11/2012].
Marchante E, Freitas H, Marchante H (2008) Guia prático para a identificação de plantas invasoras de Portugal Continental. Imprensa da Universidade de Coimbra, Coimbra, 183pp.
Silva L, Corvelo R, Moura M, Land EO, Fernandes FM (2008) Arundo donax L. In: Silva L, Land EO, Luengo JLR (eds) Flora e fauna terrestre invasora na Macaronésia. Top 100 nos Açores, Madeira e Canárias. Arena, Ponta Delgada, pp. 213-216.