Weed Watch – Reed canary grass

Reed canary grass

Reed canary grass

Reed canary grass (Phalaris arundinacea), is a tall perennial grass that grows to around two metres in height. Its leaf blades are flat and often harsh on both sides; and it has long, creeping rhizomes. Spreading flower/seed panicles rise from hairless stems and can be green, purple of brown. Reed Canary Grass is an internationally renowned weed of wetlands, where it forms dense sprawling stands up to 1m tall that smother and impede the regeneration of other vegetation. The dense mats impede access and drainage, causing silt accumulation and flooding. It can replace other aquatic margin vegetation and degrade habitat for aquatic fauna. It has the potential to take over wetland margins and the margins of other water bodies and drains, and it represents a significant threat to wetlands where it can replace native species. The plants is very hardy, it grows rapidly and it spreads easily – by both the seeds and its rhizomes. It is difficult to eradicate once established. It particularly favours moist, fertile or wet soils, including under the shade of willows and open kahikatea forest, wet grassland, margins of water bodies, wet waste areas and roadsides. It is tolerant of freezing conditions. It has been found in Canterbury gardens and ponds and its variegated version (with cream-striped leaves), is cultivated as an ornamental plant. Unfortunately, it too, has ‘escaped’ and spread widely in many places.

A weed to look out for.

A weed to look out for.

Reed canary grass was first recorded in Te Waihora lake shore wetlands in 2009. Reed canary grass is becoming a significant weed species around Te Waihora. It can now be found along the Huritini Halswell canal, Waikirikiri Selwyn river, the Silverstream catchment and in scattered patches along the lake margin. So what can you do? Establish the plant’s identity for a start. Small infestations can be physically removed but for larger areas, cutting it back several times a year may be required. In some situations, glyphosate herbicide may work but several applications will be needed.