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Yellow flag-iris

Yellow flag-iris

Yellow flag-iris

(Iris pseudacorus)

Priority: -  Contain

Tags: Aquatic | Toxic

Overview

Identification

Perennial herb that grows in 'clumps'; individual plants grow 40 cm to 1.5 m tall. This is the only yellow-flowered iris that grows in water in British Columbia. It has stout rhizomes and long, spreading roots.

Leaves are erect, flattened, and sword-like, mostly basal and are folded and clasp the stem at the base in a fan-like manner.

Flower is large, showy, and yellow. Several flowers can occur on each stem along with one or two leafy bracts. Seeds form in large, glossy green, triangular capsules. The seeds float in water.

Reproduction

Reproduces by seed and rhizome fragments.

Habitat & Ecology

Wetlands, ponds, marshes, slow-moving streams, roadside ditches. Can also grow in salt water.

Impacts

Mat-forming root mass collects sediment and severely reduces water flow. Can fill in wetlands and streams. Displaces native plants and damages wildlife habitat.

Management

Dig or hand pull small patches - this must be done for several years to deplete root reserves. Remove entire rhizome mass. As a stop gap measure, clip flowers to prevent seed development and dispersal and remove fruits to prevent them from floating downstream and creating new colonies. Plant parts are toxic and can cause skin irritation, so wear gloves and appropriate protective clothing. Take care to ensure that all plant parts have been removed from the area and disposed of by burning or placing in a thick garbage bag and take to the landfill.

An alternative method is to employ a benthic barrier. Cut plants down to the base, and lay down a heavy thick matting that will block light and weight down the rhizomes, forcing the plants to be smothered as it depletes its stored resources in an anoxic environment. The barriers should be left on for at least 70 days. This method will require follow up to ensure that plants will not regrow after barriers are removed.

Resources

Assessing Benthic Barriers vs. Aggressive Cutting as Effective Yellow Flag Iris (Iris pseudacorus) Control Mechanisms (Tarasoff et al. 2016)