Agres­sive weed on water and land

Matamata Chronicle - - Your Paper, Your Place - WAIKATO WEEDWATCH

In the first of our new Waikato Weed Watch se­ries, we look at al­li­ga­tor weed, a se­ri­ous threat to Waikato rivers, wet­lands and other wa­ter­ways as well as agri­cul­tural land.

At present al­li­ga­tor weed is lim­ited to a few sites in the Waikato, in­clud­ing the lower Waikato River, north­ern shal­low lakes and iso­lated agri­cul­tural and ur­ban sites.

It’s an ag­gres­sive, rapidly spread­ing weed that can oc­cupy a wide range of habi­tats.

In aquatic en­vi­ron­ments it can be bro­ken up and spread through­out the en­tire water sys­tem. Al­li­ga­tor weed forms buoy­ant mats and can com­pletely over­take wa­ter­ways, re­sult­ing in re­duced water qual­ity and bio­di­ver­sity.

The ef­fect on frag­ile nat­u­ral en­vi­ron­ments such as wet­lands is dev­as­tat­ing. The weed can also grow vig­or­ously on land where it com­petes with pas­ture or crops. It is toxic to stock and very dif­fi­cult to erad­i­cate.

Even the small­est of frag­ments can be a source of new growth for some time.

Al­li­ga­tor weed hap­pily hitch­hikes, ac­cept­ing rides from fish­er­men, boat­ies and other users of rivers that pick up and carry frag­ments of weed.

Ma­chin­ery used for ex­ca­va­tion or cul­ti­va­tion of land can also pro­vide a ride from one site to an­other. Ways for the public to help stop al­li­ga­tor weed’s spread in­clude:

Al­ways clean boats and equip­ment be­fore leav­ing any area you’ve been in. Good hy­giene with all soil move­ment equip­ment.

If you think you see al­li­ga­tor weed re­port it to Waikato Re­gional Coun­cil on 0800 BIOSEC (0800 246 732).

What to watch for:

Al­li­ga­tor weed has hor­i­zon­tal stems up to 10 me­tres long which float on the sur­face of water form­ing rafts or grow on to banks form­ing mat­ted clumps. Stem and leaf size vary. They can be very com­pact in lawns or grazed pas­ture, or much larger when grow­ing in water. Leaves are in pairs or whorls along hol­low hor­i­zon­tal stems. Flow­ers are white, pa­pery and clover-like, held erect on stalks.

Waikato weed watch is sup­plied by Waikato Re­gional Coun­cil.

Al­li­ga­tor weed can form mats, tak­ing over wa­ter­ways, wet­lands while on land it grows, com­pet­ing with crops.

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