Practical ecological knowledge for the temperate reader.

Yellow Flag - Iris pseudacorus

"Yellow iris is an introduced invasive species that is native to Europe, western Asia and northwest Africa. Outside its native range, it is a significant invader in freshwater and brackish cattail marshes and spreads in marshes and adjacent areas by underground rhizomes and seeds. In North America, it is now found in many US states."(USDA)
"In BC, it is found in the southern part of the province, where it occurs in marshes, ditches, sloughs, streambank and pond edges. It is a favourite plant in water gardens and artificial ponds because of its bright yellow flowers." [E-flora]

"Iris pseudacorus is a PERENNIAL growing to 1.5 m (5ft) by 2 m (6ft) at a medium rate.
It is hardy to zone (UK) 5 and is not frost tender. It is in flower from May to July. The flowers are hermaphrodite (have both male and female organs) and are pollinated by Bees, hoverflies.The plant is self-fertile.
Suitable for: light (sandy) and medium (loamy) soils. Suitable pH: acid, neutral and basic (alkaline) soils. It can grow in semi-shade (light woodland) or no shade. It prefers moist or wet soil and can grow in water. The plant can tolerates strong winds but not maritime exposure." [PFAF]


Edible Uses

See Hazards

Other Uses

The roots were once used like orris to scent linen closets. They are used also as a source of tannin and blue and black dyes. The flowers offer a yellow dye. [MPB-Duke]

Medicinal Uses

“Extracts of iris (Iris, lridaceae) rhizomes have a pungent and bitter taste. Tissue of the yellow flag iris, Iris pseudacorus, of Europe, is poisonous to man and animals, either fresh or dried, and produces unpleasant irritations of the mucous membranes, vomiting, and bloody diarrhea. Rhizoma iris was formerly a constituent of folk medicine and was considered a potent purgative. An essential oil is prepared from the roots of Iris pallida and I. germanica. After harvesting and sun-drying, the roots assume a pleasant violet-like scent which increases with time. The oil obtained by steam distillation is .'essence d'iris" or .'orris root oiL" The odoriferous principle is called "irone." Three isomers are the major component of this essential oil (Fig. 23.28). In contrast to the ionones that are widespread in nature, irones are found primarily in orris root oil. Freshly harvested rhizomes do not contain irones; the scent develops gradually over 3-4 years of storage of the root stocks. It seems unlikely that irones arise by enzymatic processes; oxidizing agents accelerate formation of these compounds. “ [Seiger PSM]


  • Analgesic (f; GMH); [MPB-Duke]
  • Analeptic (f; BOU); [MPB-Duke]
  • Antidote (f; BOU); [MPB-Duke]
  • Astringent (f; EFS); [MPB-Duke]
  • Carminative (f; EFS);[MPB-Duke]
  • Cercaricidal (1; X15880993); [MPB-Duke]
  • Diuretic (f; BOU; EFS; NAD); [MPB-Duke]
  • Emetic (f; EFS; HJP); [MPB-Duke]
  • Febrifuge (f; EFS);[MPB-Duke]
  • Insecticide (1; X15880993); [MPB-Duke]
  • Larvicide (1; X15880993); [MPB-Duke]
  • Laxative (f; EFS); [MPB-Duke]
  • Miracide (1; X15880993); [MPB-Duke]
  • Mosquitocide (1; X15880993); [MPB-Duke]
  • Purgative (f; BOU; HJP); [MPB-Duke]
  • Schistosomicide (1; X15880993);[MPB-Duke]
  • Sternutatory (f; EFS); [MPB-Duke]
  • Stimulant (f; NAD); [MPB-Duke]
  • Stomachic (f; EFS); [MPB-Duke]
  • Tonic (f; EFS); [MPB-Duke]
  • Vermifuge (f; EFS); [MPB-Duke]
  • Vulnerary (f; BIB). [MPB-Duke]



"Prefers a humus rich soil[79]. Succeeds in water up to 15cm deep[24]. Requires a moist soil, especially in early summer. Prefers a position in semi-shade[188]. Plants can be grown in quite coarse grass, which can be cut annually in the autumn[233]. A delicately scented essential oil is obtained from the dried roots[245]. Members of this genus are rarely if ever troubled by browsing deer or rabbits[233]. Some named forms have been selected for their ornamental value[187]. Special Features: Attractive foliage, Not North American native, Invasive, Naturalizing, All or parts of this plant are poisonous, Wetlands plant, Attracts butterflies, Suitable for cut flowers."[PFAF]


"Seed - best sown as soon as it is ripe in a cold frame[4]. Stored seed should be sown as early in the year as possible in a cold frame. A period of cold stratification improves germination time and rates. Prick out the seedlings into individual pots when they are large enough to handle and grow them on in the greenhouse or cold frame for their first year. Plant out into their permanent positions in late spring or early summer. Division in March or October. Early autumn is best[200]. Very easy, larger clumps can be replanted direct into their permanent positions, though it is best to pot up smaller clumps and grow them on in a cold frame until they are rooting well. Plant them out in the spring."[PFAF]

Iris Sp.

Rhizome [bulbs, fleshy roots]. Leaf: 2-ranked in basal fan; cauline 0–few, reduced, often bract-like, without development of distal portion. Inflorescence: ± flat cyme, flowers 1–many. Flower: perianth parts ± clawed; sepals generally wider than petals, spreading or reflexed, occasionally with white area in basal 3/4, this generally with smaller yellow area; petals erect; stamens free [(not)]; ovary inferior, style branches petal-like [(not)], arched over stamens, each with scale-like flap (with stigmas on inner surface) opposite stamen and just below 2-lobed tip (crest), with sepals forming 3, 2-lipped units [(not)]. Fruit: loculicidal capsule, rounded or triangular, chambers 3. Seed: generally compressed, pitted, light to dark brown (red).
± 160 species: generally northern temperate. (Greek: rainbow, from flower colors) [Wilson 2003 Syst Bot 28:39–46] Hybrids between some sympatric species; Iris germanica only sp. in California with bearded sepals. Unabridged references: [Lenz 1958 Aliso 4:1–72; Clarkson 1959 Madroño 15:115–122]

Key to Iris

Local Species;

  1. Iris missouriensis - western blue iris [E-flora]
  2. Iris pseudacorus - yellow iris [E-flora]
  3. Iris sibirica - Siberian iris [E-flora]

Uses of Iris Sp.

Iris species
Medicinal Parts: The medicinal part is the rhizome with the roots.
Habitat: Indigenous to southern Europe.
Production: Orris root is the root of Iris germanica, Iris versicolor and other varieties.
Volatile oil: chief constituent's irone, in particular alpha-, beta- and gamma-irone (odor resembling violets)
Triterpenes: Iridale (mono-, bi- and spirocyclic compounds, precursors of the irones), including among others irigermanal
Isoflavonoids: including, among others, irilon, irisolone, irigenine, tectorigenin and their glycosides including iridine Flavonoids
Xanthones: C-glucosylxanthones, for example iris xanthone, magniferin Starch
Orris root is mildly expectorant. Some of the flavonoids (in particular the isoflavon irigenin) have an inhibitory effect on c-AMP phosphodiesterase. Root extracts are said to have an ulcer-protective, spasmolytic and serotonin-antagonistic effect.
Unproven Uses: Orris has been used for disorders of the respiratory system.
Homeopathic Uses: This species has been used to treat disorders of the respiratory tract or thyroid gland, for digestion complaints and headaches.
General: No health hazards or side effects are known in conjunction with the proper administration of designated therapeutic dosages. The juice of the fresh plant has a severely irritating effect upon skin and mucous membranes. If taken internally, it can lead to vomiting, abdominal pain and bloody diarrhea. Severe inflammation occurs following mucous membrane contact.
Pregnancy: Not to be used during pregnancy.
Mode of Administration: Iris is available in homeopathic dilutions, as a constituent of various combination preparations and in various tea mixtures. [PDR]


Coville records a crafty practice of the Klamath medicine men, who would sometimes make a mixture of tobacco, dried iris root and Death Camas, and give it to a person in order to nauseate him. Then they would charge the victim a fee to make him well again ![Saunders]

Common Names
Iris, sword lily, blue or yellow flag. Toxic Principle and Mechanism of Action
All parts of the plant but especially the rhizomatous roots, bulbs, and seed capsules contain pentacyclic terpenoids such as missourin, missouriensin, and zeorin [1 ]. These compounds are irritants and cause gastroenteritis if ingested, and contact dermatitis in some people handling and contacting the sap [2,3].
Risk Assessment
Irises are commonly grown for their striking flowers and the rhizomatous roots, which grow at the soil surface, are readily accessible to pets. Rhizomes or bulbs stored over-winter in the house are always a potential source of poisoning to household pets. Clinical Signs
Excessive salivation, vomiting, and diarrhea follow the ingestion of iris rhizomes. Treatment when necessary may require intestinal protectants and intravenous fluids to counteract the effects of dehydration.[DP2]

Iris versicolor (Not a local species)

Iris versicolor L.
Blue Flag
Part Used: Rhizome
Constituents: Volatile oil, containing furfural; iridin (also known as irisin, a glycoside); acids (including salicylic and isophthalic); miscellaneous: a monocyclic C 3 I triterpenoid, gum, resin, sterols[150]
Actions: Cholagogue, hepatic, alterative, laxative, diuretic, anti-inflammatory
Indications: Blue flag is used in the treatment of skin diseases, and apparently works in this area through effects on the liver, the main detoxifying organ of the body. It is valuable as part of a wider treatment for eczema and psoriasis.
Priest and Priest described blue flag as a
''. . . positive alterative for chronic, torpid conditions: influences glandular system, lymphatics, liver and gall ducts, and intestinal glands. Specific for hepatic congestion due to venous or lymphatic stasis.''
They recommended it for chronic hepatitis, rheumatic conditions, toxic sciatica, scrophulous skin conditions, eczema, psoriasis, herpes, enlarged thyroid gland, and uterine fibroids.
Safety Considerations: No side effects or drug interactions have been reported.
Preparations and Dosage: Tincture dosage is 1 ml three times a day (1:5 in 40%). To make a decoction, put 1 teaspoon of dried herb into 1 cup of water, bring to a boil, and simmer for 10 to 15 minutes. This should be drunk three times a day.
According to the BHC, dosage is 0.6 to 2 g dried rhizome (or by decoction), 3 to 10 ml tincture (1:5 in 45%), or 0.6 to 2 ml fluid extract (1:1 in 45%) three times daily. Blue Flag, in Herbal Medicines: A Guide for Health-Care Professionals [Medical Herbalism Hoffman]

Iridaeeae, Iris Family
69. Iris versicolor L. Blue flag. Smith 9250. "Ma~k~sagre" (Medicine fast). A strong physic and a quick one. It is dangerous and must be used correctly, as an overdose would kill. For a baby, use one-half inch; for an adult, use one inch only.[Huron-Smith: Hocak]

Blue Flag (iris versicolor L.)
Poisonous Properties: The rootstock is poisonous. It contains the acrid, resinous substance irisin or iridin. When eaten, it produces nausea, vomiting, purging, and pain. It is often mistaken for the sweet flag {Acorus Calamus L.) which is not poisonous, and is masticated by some people as a cure for indigestion. When in flower, the two plants are so dissimilar that they could never be taken for one another, but in the autumn when the roots are gathered, nothing remains of the upper portion of the plants. Even then, however, they may be distinguished by their odour, the sweet flag being pleasant aromatic, while the blue flag is unpleasant and nauseous.[FPP]


Iris missouriensis - western blue iris

Many plants in this genus are thought to be poisonous if ingested, so caution is advised[65]. An arrow poison was made from the ground-up roots[207PFAF].

Plants can cause skin irritations and allergies in some people[238PFAF].

Edible Uses


Rootstocks have an acrid taste and are seldom eaten.

One of our courageous collaborators tasted the raw rootstocks and found them rather sweet at first, but they soon became "terribly astringent, causing the mouth and throat to burn." Then some rootstocks were peeled and cooked. The odor and the first taste of this cooked product were pleasant, but soon produced the same burning, unpleasant, stringent effect.


The roasted seed is a coffee substitute[177, 183PFAF]. []

Other Uses


Yields a green dye[155PFAF] (part of plant used is not specified). []

Medicinal Uses

Rocky Mountain iris was employed medicinally by several native North American Indian tribes who used it to treat various complaints, but especially as an external application for skin problems[257PFAF]. It was for a time an officinal American medicinal plant [4PFAF], but is little, if at all, used in modern herbalism.


Emetic and odontalgic [61, 257PFAF]. Caution is advised in the use of this plant, see the notes above on toxicity[KPFAF].


A paste of the ripe seeds has been used as a dressing on burns[257PFAF]. []


Iris missouriensis - Iridaceae

Chemical Part Lo PPM/ Hi PPM References
Betulinic-Acid Root [AllHerb1998]

Iris sibirica - Siberian iris


Page last modified on Sunday, February 20, 2022 3:24 AM