Pale Yellow Iris

Pale Yellow Iris (Iris pseudacorus L.)

Pale Yellow Iris is a Prohibited Noxious Weed that poses a serious risk to waterbodies and riparian areas within the County of Newell. This aquatic perennial grows along shorelines and in shallow water, where it can quickly form dense patches that are difficult to remove.

Why is Pale Yellow Iris a problem?

Poisonous to cattle
Both the foliage and underground stems of Pale Yellow Iris are toxic to cattle if consumed. The plant’s resin can also cause skin irritation in people.

Impacts water flow and infrastructure
Once established, Pale Yellow Iris forms thick clumps that trap sediment. This can narrow stream channels, restrict water flow, and clog irrigation canals and drainage systems. Its seeds may also block water control structures and pipes.

Hard to control once established
Pale Yellow Iris spreads aggressively and is challenging to manage, particularly because it grows in and around water. Herbicide options are limited in aquatic environments. Hand removal is only effective if the entire plant, including the underground rhizomes, is removed.

How does Pale Yellow Iris spread?

This species reproduces by both seeds and rhizomes. The seeds float, allowing them to travel long distances through watercourses. Underground rhizomes spread outward from the parent plant and produce new shoots, forming dense mats along shorelines. Over time, these mats crowd out native vegetation and create large, established colonies.

How to identify Pale Yellow Iris

Pale Yellow Iris typically blooms from June to early July. It has long, dark green, sword-like leaves and can grow up to one metre tall. The flowers are bright yellow with distinctive purple to brown markings. It is easiest to identify during flowering, as it is usually the only iris with entirely yellow flowers found in County of Newell wildlands.

Please report sightings

Under Alberta’s Weed Control Act, Pale Yellow Iris is classified as a Prohibited Noxious Weed and must be eradicated when found. The County of Newell Agricultural Service Board is available to help landowners identify and manage this species.

If you suspect Pale Yellow Iris on your property or in nearby waterbodies, please contact us at 403-362-3266 or submit a Vegetation Concern through the Newell Connect app.