Yellow iris (Iris pseudacorus)

Also known as: Yellow flag
GenusIris (1)
SizeFlower diameter: 8-10 cm (2)
Height: 40-150 cm (2)

Common and widespread (3).

The yellow iris is a robust plant with beautiful bright yellow flowers (4). The roots and bulbs are thick and fleshy, and the narrow sword-shaped leaves are bluish-green with a prominent mid-rib (5). Between 4 and 12 large, showy flowers are borne on a somewhat flattened stem (5); they vary in colour from pale yellow to almost orange (2). An alternative name for this species is 'segg', which derives from an Anglo-Saxon word meaning 'short sword', and refers to the shape of the leaves (4). The fluttering of the flowers was thought to resemble flags blowing in the breeze, hence the name 'yellow flag' (6).

Found throughout Britain, becoming absent on high ground in Scotland (3). It also occurs throughout much of the rest of Europe, as well as North Africa, Western Asia and the Caucasus region of south west Russia (2). Yellow iris has become widely naturalised outside of its original range, as it is so popular in gardens (3).

Common in wet habitats including wet meadows, wet woods, fens, wet dune-slacks, and the edges of watercourses, lakes and ponds. In the north and west of Britain it may also be found alongside coastal streams, on raised beaches, saltmarsh and shingle. It has in many cases been planted in the wild and escaped from gardens (3).

Yellow iris flowers from May to July (6); it reproduces by seeds as well as by vegetative reproduction(3). It is thought by some to be the origin of the 'fleur-de-lis' device used on coats of arms (4).

In folk medicine, the rhizome of yellow iris was looked upon as something of a cure-all, being used to treat coughs, convulsions, toothache, diarrhoea, cramp, and as an antidote to poisoning (6). Furthermore, the flowers were used to produce a yellow dye, and the rhizome was used to make black dye (6).

Not currently threatened.

Not relevant.

For more information on British plants and their conservation see Plantlife- the wild plant conservation charity:
Visit the website of the Botanical Society of the British Isles at:

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:

  1. National Biodiversity Network Species Dictionary (Feb 2003):
  2. Clapham, A.R., Tutin, T.G. & Moore, D.M. (1987) Flora of the British Isles. 3rd Edition. Cambridge University Press, Cambridge.
  3. Preston, C.D., Pearman, D.A. & Dines, T.D. (2002) The New Atlas of the British and Irish Flora. Oxford University Press, Oxford.
  4. Mabey, R. (1996) Flora Britannica. Sinclair-Stevenson, London.
  5. Press, B. & Gibbons, B (1993) Photographic field guide to wild flowers of Britain and Europe. New Holland Publishers (UK) Ltd, London.
  6. A modern herbal by Mrs M Grieve (Feb 2003):