|Subgenus:||Iris subg. Limniris|
|Section:||Iris sect. Limniris|
|Series:||Iris ser. Laevigatae|
List of synonyms
Iris pseudacorus, the yellow flag, yellow iris, or water flag, is a species of flowering plant in the family Iridaceae. It is native to Europe, western Asia and northwest Africa. Its specific epithet pseudacorus means "false acorus", referring to the similarity of its leaves to those of Acorus calamus (sweet flag), as they have a prominently veined mid-rib and sword-like shape. However, the two plants are not closely related.
This herbaceous flowering perennial plant grows to 100–150 cm (39–59 in), or a rare 2 m (6 ft 7 in) tall, with erect leaves up to 90 cm (35 in) long and 3 cm (1.2 in) broad. The flowers are bright yellow, 7–10 cm (2.8–3.9 in) across, with the typical iris form. The fruit is a dry capsule 4–7 cm (1.6–2.8 in) long, containing numerous pale brown seeds.
I. pseudacorus grows best in very wet conditions, and is common in wetlands, where it tolerates submersion, low pH, and anoxic soils. The plant spreads quickly, by both rhizome and water-dispersed seed. It fills a similar niche to that of Typha and often grows with it, though usually in shallower water. While it is primarily an aquatic or marginal plant, the rhizomes can survive prolonged dry conditions.
Large I. pseudacorus stands in western Scotland form a very important feeding and breeding habitat for the endangered corncrake.
I. pseudacorus is one of two iris species native to the United Kingdom, the other being Iris foetidissima (stinking iris).
The plant was rated in second place for per day nectar production per flower in a UK plants survey conducted by the AgriLand project, which is supported by the UK Insect Pollinators Initiative. However, when number of flowers per floral unit, flower abundance, and phenology were taken into account, it dropped out of the top 10 for most nectar per unit cover per year, as did all plants that placed in the top ten, with the exception of common comfrey, Symphytum officinale.
It is widely planted in temperate regions as an ornamental plant, with several cultivars selected for bog garden planting. The following cultivars have gained the Royal Horticultural Society's Award of Garden Merit:
In some regions where it is not native, it has escaped from cultivation to establish itself as an invasive aquatic plant which can create dense, monotypic stands, outcompeting other plants in the ecosystem. Where it is invasive, it is tough to remove on a large scale. Even ploughing the rhizomes is often ineffective. It has been banned in some areas but is still widely sold in others for use in gardens.
Toxicity and uses
The plant's roots and leaves are poisonous.
This plant has been used as a form of water treatment since it has the ability to take up heavy metals through its roots and is featured in many AS Level Biology practicals as its ability to grow in low pH levels makes it a useful indicator.
- "Iris pseudacorus L. is an accepted name". theplantlist.org (The Plant List). 23 March 2013. Retrieved 14 April 2015.
- "Which flowers are the best source of nectar?". Conservation Grade. 2014-10-15. Retrieved 2017-10-18.
- "RHS Plant Selector - Iris pseudacorus". Retrieved 24 June 2013.
- "AGM Plants - Ornamental" (PDF). Royal Horticultural Society. July 2017. p. 53. Retrieved 13 March 2018.
- "Roy Davidson". RHS. Retrieved 25 September 2020.
- "RHS Plant Selector - Iris pseudacorus 'Variegata'". Retrieved 7 September 2020.
- Schembri, Patrick J.; Baldacchino, Alfred E. (2011). Ilma, Blat u Hajja: Is-Sisien tal-Ambjent Naturali Malti (in Maltese). p. 81. ISBN 978-99909-44-48-8.
- Elias, Thomas S.; Dykeman, Peter A. (2009) . Edible Wild Plants: A North American Field Guide to Over 200 Natural Foods. New York: Sterling. p. 261. ISBN 978-1-4027-6715-9. OCLC 244766414.