Giant reed (Arundo donax) is an invasive plant of the grass family (Poaceae). It dominates moist, well-drained soils along ditches, rivers, lakes and floodplains. It is fast-growing, uses excessive resources and crowds out native plant species while providing little food or habitat for native birds, insects, and other animals.
Giant reed usually spreads by stem and rhizome fragments. Once established, it becomes difficult to eradicate and requires the destruction of all stems and rhizomes.
Where it's found
Giant reed has not been reported in natural ecosystems in Canada and is only present in cultivation. Known sites are under official control for eradication.
Giant reed is native to warm temperate and subtropical areas of Asia. It has been cultivated worldwide and has naturalized in countries of Africa, Europe, North and South America and Oceania. In the United States, it has been introduced in many southern states. It uses large amounts of water and is commonly found along waterways. However, it can tolerate a broad range of conditions and can also be found in agricultural areas, forests, grasslands, scrublands, coastlands, deserts and roadsides.
How to spot it
-
Tussock -
Stem and leaves -
Flower head -
Variegated form -
Ligule -
Spikelet
Giant reed is a perennial grass with strong rootstalks and erect stems that can grow up to 10 m tall. Stems are hollow and 1-3.5 cm thick. Leaves are alternately arranged in two vertical rows on opposite sides of the stalk, blue-green in colour, and 30-100 cm long. The seed heads are plume-like and 30-65 cm long. The units of the seed heads, or spikelets, have hairy lower bracts (lemmas). Ornamental varieties of giant reed exist. A popular one is distinguished by its white and green-striped leaves, and typically attain heights ranging from 1 to 5 metres, making it shorter than the "wild" form.
Giant reed is often confused with common reed (Phragmites australis). Giant reed has longer and broader leaves, a thicker stem and can grow taller than common reed. Also, the ligule, a thin membrane found at the base of the leaf blade, of giant reed has shorter hairs than that of common reed. When in flower, giant reed has hairy lemmas while those of common reed are hairless.
How it spreads
In North America, giant reed is not known to produce seeds. Instead, it spreads by stem and rhizome fragments. Intentional planting is a key factor in its spread. This plant can also be dispersed along waterways by storms, floods, machinery, boats, construction activities, and the moving and dumping of soil or garden waste. These events spread plant fragments and cause new colonies to form.
What you can do
- Avoid planting or distributing invasive plants
- Do not dump garden waste in parks, fields, forests or other natural areas
- Ensure machinery, vehicles and tools are free of soil and plant parts before moving them from one area to another
- Declare all plants and related products when returning to Canada
- If you think you've spotted giant reed, report it to the Canadian Food Inspection Agency (CFIA). The CFIA will follow up and determine if further action is needed.
What we are doing
Giant reed is regulated as a pest in Canada under the Plant Protection Act. Importation and domestic movement of regulated plants and their propagative parts is prohibited.