Iridaceae (iris) family
Where is it originally from?
Europe, Asia, North Africa
What does it look like?
Clump-forming perennial to 80 cm with red-brown rhizomes (up to 15 mm diameter). Leathery, dark green leaves (15-25 mm x 60-100 cm) are broad, sword-shaped, and foul-smelling when crushed. Erect flowering stems (60-80 cm) with dull yellow flowers (up to 10cm diameter) with greenish-brown markings (occasionally brownish-purple) are produced from November to December, followed by green, 3-sided seed capsules (5 cm long) that split open to release many round, scarlet seeds (5 mm diameter).
Are there any similar species?
Many Gladiolus and related species, and four other exotic Iris species, all of which have been found in the wild, are similar. I. pseudacorus is the only aquatic species with tall stems and yellow flowers.
Why is it weedy?
Tolerant of deep shade, hot or cold, most soil types and drought and semi-damp conditions. Disperses widely and forms dense long-lived clumps. Unpalatable and toxic to livestock and recovers from damage.
How does it spread?
Birds spread the seeds, and rhizome fragments are spread by water. Both are spread by contaminated machinery, soil and dumped vegetation. Often found on roadsides and wasteland.
What damage does it do?
Smothers the ground, preventing the establishment of native plant seedlings. Poisonous seeds may affect birdlife.
Which habitats is it likely to invade?
Heavily disturbed forest and margins, shrubland, fernland, bare ground and gullies.
What can I do to get rid of it?
1. Cut down and paint stump: glyphosate (333ml/L + penetrant).
2. Stem injection (all year round): 5 ml undiluted glyphosate into each stem base.
3. Spray (spring-autumn): glyphosate (10ml/L + penetrant) or triclopyr 600 EC (10ml/L) or triclopyr 120g/L (50ml/L).
4. Weedmat: cut tops, lay, leave 3-4 months.
What can I do to stop it coming back?
Bared areas, both shady and open, can be reinfested from the seed bank, and rhizomes can resprout, hard to kill. Exclude livestock at all times. Remove seeds if ripe, dispose. Replant with taller understorey species in forest sites, to minimise seedlings.