Yellow Flag

Also known as:
Yellow Iris
Europe, Asia, North Africa

General description

Perennial semi-aquatic <2m high. Thick creeping rhizomes with many rootlets. Forms dense floating mat in shallow water. Broad flat sword shaped leaves, in fans from reddish base. Yellow to golden-orange flowers (Oct-Dec) on stalks. Seed capsule with many smooth, flattened seeds. Plant dies back in winter.

Still fresh or brackish water: swamps, salt marshes, pond edges.Tolerates frost, flooding, drought, high or low water fertility, many soil types.

Seeds dispersed by wind. Vegetative spread from rhizome fragments.

Highly toxic to humans & livestock. Crowds out other species. Impedes drainage, disrupts recreational activity.

Site management

In narrow waterbodies, lower light levels with riparian planting. Exclude livestock. Begin control at margins, prevent seeding, work upstream to downstream where possible. Requires follow up.

Recommended approaches

1. Dig out small infestations removing all rhizomes.
2.Stem inject (5 ml undiluted glyphosate) into each stem at base, all year round.
3. Weed wipe, spring to autumn, (300ml glyphosate + 2ml penetrant/1L).
4. Spray terrestrial sites, spring to autumn (100ml glyphosate + 20ml penetrant/10L).
5. Spray aquatic sites, spring to autumn (100ml glyphosate/10L, use glyphosate formulation approved for use over water).

Caution: when using any herbicide or pesticide PLEASE READ THE LABEL THOROUGHLY to ensure that all instructions and safety requirements are followed.

Similar species

stinking iris
Iris foetidissima

Stinking iris is not aquatic. It is a smaller plant with dull yellow-green flowers. Its crushed leaves have a foul smell.

RPMS status

Surveillance - Whole Region
National Pest Plant Accord species - nationwide
yellow flag - Main species image