Yellow flag iris - Iris psuedocorus
Yellow flag iris is an invasive aquatic plant species found in Lincoln County. It is considered aquatic because it can survive and thrive with the below ground portion of the plant under submerged conditions for long periods of time. Yellow flag iris has the capacity to invade and severely impair wetlands, rivers and streams. These aquatic habitats are typically sensitive wildlife areas which makes control of invasive plants particularly challenging. Yellow flag iris is a State Listed B noxious weed due to its abundance in other parts of Oregon but in Lincoln County its relatively sparse presence make it a priority species for early detection and control. Currently the ISCP is inventorying infestations of yellow flag iris within rivers, streams and wetlands throughout Lincoln County. If you know an infestation contact our Program Manager (541-265-2631).
Physical Description
Yellow flag iris is the largest (up to 5-6 ft) iris species found in Lincoln County, towering over any other varietals and natives. It is a perennial native to Europe that was introduced as a garden plant, and a water treatment species (accumulates heavy metals) in the United States. It spreads by dislodged fragments of its underground rhizome (see photo below) or by its corky seeds that can float. During late spring months its yellow flowers are a good identifier. A good place to see this species in Lincoln County is at Brian Booth State Park, formerly known as Ona Beach State Park.
Physical Description
Yellow flag iris is the largest (up to 5-6 ft) iris species found in Lincoln County, towering over any other varietals and natives. It is a perennial native to Europe that was introduced as a garden plant, and a water treatment species (accumulates heavy metals) in the United States. It spreads by dislodged fragments of its underground rhizome (see photo below) or by its corky seeds that can float. During late spring months its yellow flowers are a good identifier. A good place to see this species in Lincoln County is at Brian Booth State Park, formerly known as Ona Beach State Park.
Why is yellow flag iris a problem?
Yellow flag iris is a very large and aggressive species that grows quite successfully in standing water such as in wetlands and streams. Its thick growth outcompetes and replaces the native vegetation that wetland birds and wildlife depend upon for food and shelter. In quick moving systems such as streams, this species can overtake and choke waterways and alter the flow regime causing flooding or abnormal flows. Yellow flag iris does not provide a food source to wildlife and displaces existing sources such as native sedges and rushes.
How do I get rid of it?
Control is extremely difficult and tricky if the plant is found in submerged conditions (along streams or wetlands). Killing or removing the underground rhizome is necessary but in moving water, digging can spread rhizome fragments. Herbicides have been shown to be effective to control of yellow flag iris, but licensed applicators are typically required to purchase the type of herbicide permitted in these areas. Prevention of seed spread can be done by cutting mature flowers during the flowering season. The sap within the tissue of this plant can cause temporary skin irritation. If found in non-submerged conditions, careful and thorough digging will work but due to the sheer amount of material, mechanical means may be required.
Yellow flag iris is a very large and aggressive species that grows quite successfully in standing water such as in wetlands and streams. Its thick growth outcompetes and replaces the native vegetation that wetland birds and wildlife depend upon for food and shelter. In quick moving systems such as streams, this species can overtake and choke waterways and alter the flow regime causing flooding or abnormal flows. Yellow flag iris does not provide a food source to wildlife and displaces existing sources such as native sedges and rushes.
How do I get rid of it?
Control is extremely difficult and tricky if the plant is found in submerged conditions (along streams or wetlands). Killing or removing the underground rhizome is necessary but in moving water, digging can spread rhizome fragments. Herbicides have been shown to be effective to control of yellow flag iris, but licensed applicators are typically required to purchase the type of herbicide permitted in these areas. Prevention of seed spread can be done by cutting mature flowers during the flowering season. The sap within the tissue of this plant can cause temporary skin irritation. If found in non-submerged conditions, careful and thorough digging will work but due to the sheer amount of material, mechanical means may be required.
