Pretty but also de­struc­tive

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

There’s no doubt that yel­low flag iris is a pretty, eye catch­ing plant.

Un­for­tu­nately, it’s as de­struc­tive as it is pretty. Yel­low flag iris is preva­lent in gar­dens through­out the Waikato.

This na­tive to Europe, Asia and North Amer­ica was in­tro­duced to New Zealand as an or­na­men­tal gar­den plant. It has also been de­lib­er­ately planted around wa­ter­ways and wet­lands in many ar­eas.

The plant’s seeds and rhi­zomes are spread by wa­ter move­ment and ma­chin­ery to in­fest new ar­eas. Yel­low flag iris is tol­er­ant of many cli­matic ex­tremes and grows hap­pily in any open, sunny swampy ground, fresh or brack­ish wa­ter mar­gins, lakes, salt marsh, and wet sandy ar­eas – even in pad­docks near wa­ter­ways or wet­lands.

The rhi­zomes form dense float­ing mats, dis­plac­ing na­tive plants and caus­ing flood­ing. Poi­sonous seeds may also af­fect na­tive birdlife. Iden­ti­fy­ing fea­tures in­clude yel­low flow­ers up to 120 mil­lime­tres across, typ­i­cally in an iris like form, flow­er­ing in spring and early sum­mer.

Hamil­ton Lake has his­tor­i­cally been in­vaded by yel­low flag.

Waikato Weed Watch is sup­plied by Waikato Re­gional Coun­cil.

Yel­low flag iris.

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