Yellow flag iris

Yellow flag iris is a perennial herb about 1.5m tall with rhizomes and bright yellow flowers. It displaces native vegetation, alters river flow, and is poisonous to livestock.

Description

Leaves are sword-shaped and arise in a fan-like arrangement from the base of the plant.
Flowers are golden yellow, less than 12cm in diameter, and grow on erect stalks and occur in mid-spring and early summer.
Seed capsules are green and contain dark brown disc-shaped seeds.
Seeds are dispersed by wind and water. Vegetative spread occurs from rhizomes, dispersed by water.
Human-mediated dispersal occurs through contamination of machinery and deliberate plantings.
Habitats include wetlands, damp ground, pastures, and in or along still and slow-moving water bodies.

What you need to know

Forms dense mats, displacing vegetation. Accumulates sediment, altering stream flow and morphology. Impedes pasture drainage and is poisonous to livestock.

Management approach

Yellow flag iris is declared an unwanted organism by the Ministry for Primary Industries (MPI) because it is capable of causing harm to the natural environment, physical resources or human health in Aotearoa/New Zealand.

These species pose a high risk to our environment, economy, recreation, and cultural values.

Rules

Any species declared a pest, including unwanted organisms, cannot be sold or be in a place where plants are being sold. Pest plants cannot be propagated, bred, multiplied, communicated, released, caused to be released, or otherwise spread.

Consider removing this invasive species from your property and consult your local council for appropriate disposal. Consider lower-risk alternatives for your garden, such as native plants.

Control

Site management

Follow up treated areas three times per year.

Physical control

Dig or pull plants out.

Plant parts requiring disposal: seeds and rhizomes.

Contact your local council for appropriate disposal locations.

Chemical control

Certified handler/experienced agrichemical user: For terrestrial infestations use foliar spray spring to autumn 100ml glyphosate per 10L of water and 20ml penetrant.

For aquatic infestations, use foliar spray spring to autumn 100ml glyphosate per 10L of water.

Caution: When using any herbicide or pesticide please read the label thoroughly to ensure that all instructions and safety requirements are followed.

Biological control

Biological control is currently not available for this species.