Pretty but also destructive
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.