Yellow flag iris
Iris pseudacorus
Botanical family: Iridaceae
Iris pseudacorus, the only wild yellow iris of Europe, is an upright freshwater plant (60 cm to 1.5 m) with large typical bright-yellow flowers (the floral emblem of the royal coat of arms of France, the 'fleur de lys'). Natural habitat: riverbanks, marshes, damp ditches. A structuring plant of the permaculture pond.
Sun to partial shade
Mud of a pond or basin, a ledge 5-20 cm below the water
Emergent plant, feet permanently submerged
Very hardy (-25 °C)
Overwinters in your zone
Insect-pollinated (bright yellow flowers May-June, nectar-rich)
Role in permaculture
A classic companion of the edible pond: dazzling yellow flowering in May-June (a major nectar plant of early summer), a refuge for dragonfly larvae and amphibians, roots that stabilise the banks. A native species (not listed as invasive in France), but vigorous: contain it in a basket in a small pond. A documented phytopurification plant (absorbs nitrates and moderate metals).
Good companions
Traditional companion planting (benefit not demonstrated)
Insects attracted or useful
Seasons & availability
A waterside perennial set out by dividing the rhizome in spring or autumn, the yellow flag opens its yellow flowers from April to July in the ponds of temperate France.
Available: April, May, June, July.
Guidance for the oceanic / temperate climate; it may vary with your region, altitude, exposure and growing method.
Sources
- Tela Botanica, « Iris pseudacorus L. » (tela-botanica.org/bdtfx-nn-35960-description)
- Plants For A Future, « Iris pseudacorus » (pfaf.org/user/Plant.aspx?LatinName=Iris+pseudacorus)
- Missouri Botanical Garden, « Iris pseudacorus » (plantfinder.mobot.org/PlantFinderDetails.aspx?taxonid=281137)
Nutritional & medicinal properties
For educational purposes. Not a substitute for medical advice. Effects depend on the form, the dose and personal context.
Precautions & contraindications
Entirely TOXIC plant: stems, leaves, and rhizome contain a glycoside and acrid emetic substances that can cause vomiting and diarrhoea (sometimes bloody) if ingested. The rhizome also contains an irritating resinous substance, irisin, and an alkylated para-quinone is said to be responsible for dermatitis on simple contact: preferably handle it with gloves, and wash your hands after touching the rhizomes. The toxicity persists even after drying and affects mainly livestock (fodder). No food use: NEVER confuse it with the cattail at the young-shoot stage, both growing side by side at the water's edge; if in any doubt, eat nothing. A risk of confusion too, outside flowering, with sweet flag (Acorus calamus), whose foliage is also strap-like. Sources: Plants For A Future, “Iris pseudacorus”; Toxiplante, “Iris pseudacorus L.”; Tela Botanica, “Iris pseudacorus L.” and “Typha latifolia L.” (Coste's flora).
Species & varieties
The best-known species and varieties in France.
Common varieties
Voices of peoples
Paraphrases attributed to their documented sources. Never an invented quote.
Medieval French heraldic tradition · Kingdom of France, 12th century onward
According to the Golden Legend, King Clovis, surrounded by the Visigoths near the river Vouglé, saw yellow flag irises in bloom point out to him a passable ford. Saved, he adopted the flower as an emblem. The heraldic fleur-de-lis of the Capetian kings is said to represent a stylised Iris pseudacorus, not the cultivated lily, although the confusion has crossed the centuries.
François Couplan, Le régal végétal, Sang de la Terre, 2009 ; Michel Pastoureau, Une histoire symbolique du Moyen Âge occidental, Seuil, 2004.
Key takeaways
- • Prefers sun to partial shade exposure.
- • Ideal soil: mud of a pond or basin, a ledge 5-20 cm below the water.
- • Classic companion: Cattail (bulrush).