Know your alien invasive plants: Yellow Flag Iris

The flower of a Yellow Flag Iris or Iris pseudacorus alien invasive plant. PHOTO:

THIS week, Hillcrest Conservancy takes a look at the Yellow Flag Iris as part of its series of articles on alien invasive plants to help the community to identify and eradicate them from their gardens.

The Yellow Flag Iris’ scientific name is Iris pseudacorus but it is also known as the Yellow flag, Yellow iris or geel iris (Afrikaans).


A Yellow Flag Iris or Iris pseudacorus alien invasive plant. PHOTO: Pinterest.



The Yellow flag iris forms dense growth along riverbanks and the fringes of ponds, competing with indigenous species and altering water flow.

It is a perennial moisture-loving plant with yellow flowers with three narrow and three broad lobes 70mm long and 40mm wide.

The leaves are long, strap-like, green to bluish-green and erect, with the upper part bending over. The leaves are 1m long and 30mm wide which reaches a height of 100-150cm.

The fruit/seeds are glossy green three-angled capsules which are 40-80mm long.


Where does this species come from?

Europe, western Asia and parts of North Africa.


What is its invasive status in South Africa?

NEMBA Category 1a.


Where in South Africa is it a problem?

Mostly recorded from Gauteng Province and common around some wetlands in Johannesburg and Pretoria.


How does it spread?

Rhizomes spread the plant, as well as seed dispersal. Seeds are spread along by flowing water.


Why is it a problem?

This partially aquatic plant forms dense growth along riverbanks and ponds, competing with indigenous plants and altering the flow regime of rivers. This plant also has toxic properties and is poisonous to livestock.


Does the plant have any uses?

Planted as a pond ornamental.

Ian Pattrick, Hillcrest Conservancy

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