Yellow flag iris, Iris pseudacorus, is part of the iris family (Iridaceae). Members of this family produce regular, bisexual flowers with parts in multiples of three. There are over 2,200 species in this family.
Yellow Flag Iris originated in Europe, Western Asia, and Northwest Africa. It was introduced to North America in the early 1900s as an ornamental garden flower. It has since spread throughout Canada and the U.S. It can be found in several ponds and streams across Prince Edward Island.
Yellow flag iris is an emergent aquatic plant that is drought tolerant. Positively identifying yellow flag iris can be difficult, especially when it is not in bloom. Here are some distinguishing features to look for:
Vigorous and aggressive growth habit, much more so than native iris species.
Leaves are sword-shaped, 0.5-1.5m long, 1-3cm wide, and have a raised ridge in the middle of the leaf
Large yellow flower with 3 petals facing up and 3 petals hanging down
Brown-purple stripes on petals.
Blooms June to August.
Flowers yield seed pods that resemble small green bananas.
Creates dense mats.
Extensive root system of connected rhizomes.
What it does in the ecosystem
Yellow flag iris is a popular garden ornamental that escapes from gardens into wet areas such as ditches, wetlands, and around streams and ponds.
In these environments, it is an aggressive invader that forms dense thickets harming native plants and wildlife.
When established in ditches, they can raise ditch elevation, resulting in flood control issues.
The seeds have also been known to clog up drainage intakes and irrigation pipes.
Its dense underwater root network can have up to 100 flowering plants connected.
The roots collect sediment coming downstream and harden the banks of rivers, restricting water flow by adding an average of 10 inches to the river’s edge annually.
This can result in a dried-up system, reducing the amount of open water for fish passage and waterfowl feeding.
It impacts the availability of food resources for wildlife by replacing native plants such as cattails, sedges, and rushes
This iris is unpalatable to many species, toxic to humans and pets, and has sap which can cause contact dermatitis
Before selecting a control method, consider
The size of the infestation.
The amount of effort you are willing to expend.
Often, multiple control methods are used simultaneously.
Consider the local ecosystem and what other organisms or ecological processes may be affected by management.
Consider any cultural or socio-economic impacts of your selected control method, such as impacts to landowners, indigenous groups, or other activities in that area
In watercourses, we recommend targeting control efforts upstream.
Seeds from this plant that float downstream will establish new populations, recolonizing downstream control areas and frustrating efforts.
We recommend targeting small populations that have established away from the larger outbreak first.
These have the greatest potential to spread the infestation outward and are easiest to manage when small.
BUFFER ZONE CONSIDERATIONS
If managing an invasive species near a watercourse or waterbody, you are required to obtain a Watercourse, Wetland and Buffer Zone Activity Permit from the PEI Department of Environment, Energy, and Climate Action.
This permit should be applied for at least six weeks prior to beginning management activities to allow for processing time.
It is unlawful to apply herbicides within 15m of a wetland or watercourse on PEI.