Iris pseudacorus

Iris pseudacorus L.

Family: Iridaceae Common name: yellow flag, yellow iris Category: proposed 1a (NEMBA)

Iris psedacorus flower

Description

Herbaceous perennial, 1-1.5 m (or a rare 2 m) tall. Leaves are sword-shaped, green to blue green, erect, flattened with a raised midrib, to 1 m long, about 10 per ramet (individual member of clone). Rhizomes pink in color. Flowers showy, large, with typical iris structure, yellow with brownish mottled markings upper surfaces. Flowering occurs in spring or early summer. The fruit is a dry capsule 4-7 cm long,with numerous pale brown seeds. This species is similar to some indigenous species. The table below describes some of Iris psedacorus distinguishing features to Morea huttonii, and indigenous species.

Iris psedacorus leaves and flowers

Distribution

Yellow flag is native to North Africa, Europe and Asia. It is now naturalized in Australia, South America and North America. This species is invasive in many temperate parts of the world.

How it spread

Iris pseudacorus spreads rapidly through both rhizome and water-dispersed seed. It fills a similar niche to that of Typha ( species) and often grows with it, though usually shallower water. While it is primarily an aquatic plant, the rhizomes can survive prolonged dry conditions and grow again in the rainy season.

Iris psedacorus seed capsules

History in South Africa

Yellow-flag was introduced in South Africa as an ornamental plant. It has been recorded in few localities in the country according to SAPIA database, in Vaal River between Vereeniging and Vanderbijlpark in 2004, in Limpopo it has been recorded at Klein Kariba and in 2010 it was recorded in Aquestria (Gauteng).

Environmental and economic impact

Yellow flag invades wetland and riparian communities. Yellow-flag is a fast growing and fast spreading weed,creates thickets in water just like cattail(dense stands).Iris pseudacorus is poisonous if ingested and may cause irritation to the skin when handled.

How to eradicate

There are no herbicides registered for this plant in South Africa. It can be physically controlled by hand removal, but caution should be used if pulling out this plant because it can cause skin irritation; remove seed pods to help control population expansion; dig up small infestations; remove entire rhizome; burn where conditions allow. Although a number of insects and pathogens are known to attack yellow flag, no biological control agents are presently known.

What can you do to help?

Report sightings of these plants to the Early Detection and Rapid Responce Programme (EDRR) at SANBI. We will need to know its locality (the exact locality, supply any landmarks of GPS information if possible).

Contact details

Kanyisa NyafuEmail address: alienplants@sanbi.org.za Tel: 021 799 8762

References

• Cody, W.J. 1961. Iris pseudacorus L. escaped from cultivation in Canada. Canadian Field Nat., 75: 139-142. available on line at:
• Falinska, K. 1986. Demography of Iris pseudacorus L. populations in abandoned meadows. Ekol. Polska 34(4):583-613. available on line at: http://aquat1.ifas.ufl.edu/seagrant/iripse2.html
• Goldblatt, P. and Manning, J. C. 2008. The Iris Family: natural history and classification. Timber Press, Portland.
• Invasive plants council of BC avail. On line at http://
• South African Plant Invaders Atlas. 2010. SAPIA News no. 17. ARC-Plant Protection Research Institute.
• South African Plant Invaders Atlas. 2009. SAPIA News no. 10. ARC-Plant Protection Research Institute.
• Sutherland W.J. 1990. Iris pseudacorus L. Journal of Ecology, Vol. 78, No. 3.

See more information about this series and categories of alien invasive plants

Compiled by Buhle Mthembu and Thulisile JacaJune 2011