What does it look like?
Giant reed is a bamboo-like grass that can grow to 8m tall. It has a very strong, dense root structure that spreads outwards and downwards. Leaves are bluish-green or white-striped, and fluffy seedheads grow at the tops of the stems.
Giant reed can grow in a range of soil types but prefers areas where the soil does not dry out completely, like moist forests, shrublands, roadsides, wastelands, domestic gardens, rivers, streams, and lake edges. It can also tolerate semi-saline conditions growing on the banks of estuaries and coastal areas.
Why is it a problem?
Giant reed is a very fast-growing, aggressive species that can out-compete native plants and form dense stands. It can alter ecological and successional processes and change habitats. It is tolerant to different climates and can survive and grow at almost any time under a wide variety of environmental conditions. The horizontal rhizomes (roots) of giant reed allow it to grow outwards to form large colonies, and it also grows from plant fragments.
Control methods
Physical control
Smaller clumps can be dug out by hand and disposed at a refuse transfer station or burnt.
Herbicide control
Cut off and spray regrowth with 3% glyphosate (300ml per 10L water). Respray for up to 4 years. Or
Cut down close to ground and spray the regrowth with 150ml Haloxyfop + 50ml crop oil per 10L water before it reaches 60 cm. Continue respraying at under 60 cm until regrowth ceases. This normally requires 4-6 treatments. Or
Stray emergent shoots can be cut at ground level and injected with 10 ml of undiluted Amitrole into each stem. Minimise herbicide contact with the soil and other vegetation as Amitrole is non-selective, residual, and corrosive.
Follow up frequently to check for regrowth.
CAUTION: When using any herbicide or pesticide, PLEASE READ THE LABEL THOROUGHLY to ensure that all instructions and safety requirements are followed.
Related links
- https://apps.mpi.govt.nz/applications/nzpests-view/Article/1010/Giant-reedMinistry%20for%20Primary%20Industries
- https://www.nzpcn.org.nz/flora_details.aspx?ID=3474
- https://www.nzflora.info/factsheet/Taxon/Arundo-donax.html
- https://www1.maf.govt.nz/uor-cgi/uor.pl/show?species_id=95
- https://www.weedbusters.org.nz/what-are-weeds/weed-list/giant-reed
- NPPA and the control of weeds | NZ Government
Management Programme
National Pest Plant Accord (NPPA)
The NPPA is designed to prevent the sale, distribution and propagation of a set list of pest plants (the Accord list) within New Zealand. If allowed to spread further, these pest plants could seriously damage the New Zealand economy and environment.
More informationUnwanted Organism
An unwanted organism is any organism that's capable of causing harm to natural or physical resources (like forests and waterways) or human health. A number of introduced pests in New Zealand are classed as unwanted.
Taxonomies
FamilyPoaceae
TypePlants
GroupGrass
HabitatLand
Management ProgrammeNational Pest Plant Accord (NPPA)Unwanted Organism
