Gi­ant reed

Arun­dodonax

NZ Lifestyle Block - - Tales Of A Country Vet -

THIS WAS orig­i­nally im­ported as an or­na­men­tal reed to make a strik­ing ad­di­tion to the gar­den but it quickly es­caped. Gi­ant reed, also known as ele­phant grass, forms a large, 5-8m-high clump of bam­boo-like canes clothed in long, thin, grey-green leaves. A var­ie­gated form with cream and green leaves ( Arundo donax var. ver­si­color) is also a pop­u­lar gar­den spec­i­men. Outer stems tend to droop at the edge of clumps where they are not sup­ported by the mass of canes, while the woody stems start out erect, then be­come semi-lax over time. At­trac­tive, fluffy ter­mi­nal flow­er­heads ap­pear in au­tumn.

Gi­ant reed forms dense thick­ets that slowly crowd and shade out other more de­sir­able plants. It spreads from root frag­ments, either through soil move­ment or dump­ing of gar­den waste, and al­though it rarely sets seed at present, there is con­cern that this may change in fu­ture. Gi­ant reed is a po­ten­tial wet­land weed and can af­fect aquatic na­tive fauna. It is also ca­pa­ble of block­ing drains and streams and caus­ing pipe dam­age and flood­ing.

HOW TO GET RID OF IT

Cut it down close to the ground and spray the re­growth with 10 ml/l Amit­role + 10 ml/l Gal­lant + pen­e­trant be­fore it reaches 60cm. Con­tinue re­spray­ing when it’s un­der 60cm un­til re­growth ceases (nor­mally 4–6 treat­ments). Min­imise her­bi­cide con­tact with the soil and other veg­e­ta­tion as Amit­role is non-se­lec­tive, resid­ual and cor­ro­sive. Stray emer­gent shoots can be cut at ground level and in­jected with 10ml of undi­luted Amit­role into each stem. Smaller clumps can be dug out by hand and dis­posed of at a refuse trans­fer sta­tion or burnt. Fol­low up fre­quently to check for re­growth.

MIL­TON MUNRO is a soil and plant sci­en­tist for ru­ral sup­ply com­pany PGG Wright­son. He looks at com­mon pas­ture weeds you’ll find on your block and how to deal with them.

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