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Introduction
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 (AL, AR, CA, CT, DC, DE, FL, GA, ID, IL, IN, KS, KY, LA, MA, MD, ME, MI, MN, MO, MS, MT, NC, NE, NH, NJ, NV, NY, OH, OR, PA, RI, SC, TN, TX, UT, VA, VT, WA, WI, WV) and Canadian provinces (BC, MB, NB, NF, NS, ON, PE, QC) (USDA 2010). 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.
Species Information
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General: Perennial herb from a thick rhizome; flowering stems usually simple, sometimes branched, 50-150 cm tall.
Leaves: Mostly basal, linear-lanceolate, 50-90 cm long, 1-3 cm wide, entire, the tips long-pointed.
Flowers: Inflorescence of (2) 4 to 12 showy flowers on stout, 2- to 5-cm long stalks; flowers pale to deep yellow, the tubes flared above, 1-1.5 cm long; petals erect, narrowed at the middle, about 2-3 cm long, 4-8 mm wide, the bracts herbaceous, the margins translucent; sepals broadly rounded, 5-7.5 cm long, 2-3 cm wide, bent back; style branches 2-2.5 cm long, the crests less than 1/2 as long; stigmas rounded.
Fruits: Capsules, cylindrical, 4-8 cm long; seeds numerous.
1. Flowers yellow; plants usually more than 1 m tall.................Iris pseudacorus
1. Flowers predominantly blue, purple, or white; plants usually less than 1 m tall.
2. Principle leaves usually more than 1 cm wide; petals (standards) 0.5-2 cm long, sharp-pointed; plants occurring N of 60 degrees N, also SE AK and YK..............Iris setosa
2 Principle leaves 1 cm wide, or less; petals (standards) 3-6 cm long, blunt-tipped; plants occurring in S BC
3. Blades of sepals (falls) oblanceolate; bracts green or reddish and not papery at flowering time...................Iris missouriensis
3. Blades of sepals (falls) broadly rounded; bracts brown and papery at flowering time......................Iris sibirica
Source:The Illustrated Flora of British Columbia
Habitat / Range
Moist ditches, sloughs, marshy meadows and streambanks in the lowland and steppe zones; frequent garden escape in S BC; introduced from Europe.
This species is listed by the Greater Vancouver Invasive Plant Council of the twelve most problematic species in the Vancouver region. For further information about control of this species, visit their web site. It is also listed as one of the top fourteen species of concern by the Coastal Invasive Plant Committee. Visit their web site.
Ecology
Ecological Framework for Iris pseudacorus
The table below shows the species-specific information calculated from original data (BEC database) provided by the BC Ministry of Forests and Range. (Updated August, 2013)
