Western blue flag [Iris missouriensis Nutt.][Bayer code: none][CDFA list: C] Photographs

Douglas iris [Iris douglasiana Herbert][Bayer code: none][CDFA list: C] Photographs

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SYNONYMS:western blue flag: wild iris

GENERAL DESCRIPTION:Perennials with creeping rhizomes, showy flowers, and tall, erect, sword- or grass-like leaves. Both species are native to California and under most circumstances are not troublesome weeds. However, in highly disturbed places, such as heavily grazed meadows and some forestry sites, these hardy plants can aggressively proliferate and form extensive, dense stands as other native plants decline. Leaves and rhizomes are toxic if ingested, but rarely consumed by livestock because of the bitter taste.

SEEDLINGS:Leaves similar to those of mature plants, but much smaller.

MATURE PLANT:Leaves alternate, oriented in 1 plane, parallel-veined; with bases overlapping, sheathing and sharply folded along the midvein. Leaf surfaces covered with a waxy cuticle.

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ROOTS and UNDERGROUND STRUCTURES:Rhizomes tuber-like, creeping, with shallow fibrous roots.

FLOWERS:Parts in 3’s. Stigmas flat, scale-like on the underside of the petal-like style branches.

FRUITS and SEEDS:Capsules oblong, 3-chambered. Seeds numerous, vertically compressed, in 1 or 2 rows in each chamber.

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PROPAGATION/PHENOLOGY:Reproduce vegetatively from rhizomes and by seed. Leaves die back during periods of drought or below freezing tempertatures.

MANAGEMENT FAVORING/DISCOURAGING SURVIVAL:Reducing disturbance aids survival of other native species and helps keep iris populations in check.

SIMILAR SPECIES:Yellowflag iris [Iris pseudacorus L.][IRIPS], a yellow-flowered introduction from Europe, can be troublesome in moist soils near pond margins, irrigation ditches, and wetland sites in the San Francisco Bay region and southern San Joaquin Valley. Only yellowflag iris has all of the following characteristics: rhizomes 3-4 cm diameter, branched flower stems 50-150 cm tall, stigmas rounded, leaves 1-2.5 cm wide, capsules 5-8 cm long. To 100 m (330 ft). In addition, there are at least 11 other native Iris species in California. However, these species are typically not weedy and do not have all of the highlighted characteristics listed for each species above.

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Prevention and control: These Iris spp. are native to California, but have been reported as problematic in some heavily grazed meadow and pasture areas of the state. Iris missouriensis grows in montane areas, usually in moist sites, but I. douglasiana occurs more in open fields and along the coast, generally in areas that are not wet. It tends to intergrade inland in a complex pattern associated with I. macrosiphon, I. purdyi and perhaps I. fernaldii, none of which survive in wet areas.
Western blue flag has been reported to be toxic to livestock, but both species are highly unpalatable and poisoning is very rare. These species can withstand heavy trampling due to rapid regeneration from rootstocks. Overgrazing and excessive trampling result in a weakening of other vegetation, and allow Iris to increase, thus becoming a problem to ranchers. Dense stands of iris may also result in reduced quality of wildlife habitat. Meadow forbs are an important component of the meadow sage grouse diet, and may decline where Iris is overabundant.
It is important to recognize that these Iris spp. are a natural component of the meadow ecosystem, and should not be eradicated. However, in situations where they have become the dominant species, employing management strategies may be beneficial for both ranchers and wildlife. There are, however, limited solutions for iris management after it has become a problem. Therefore, the best solution is to develop a grazing management plan, which prevents livestock from excessive meadow utilization. At minimum, a rough estimate of iris populations should mapped, to determine their initial distribution. Subsequent observations should be made to determine if Iris appear to be increasing. Rapid increases in the population may be an indication of overuse of the meadow, and the current grazing strategy may need to be modified.
In situations where iris dominate the meadow composition, a more aggressive strategy may be needed. Iris plants may be hand dug and the roots exposed in the sun to dry. Grazing should be deferred until grasses and forbs recolonize the disturbed areas. Iris may also be suppressed by mowing. However, regrowth will likely occur, especially if soil moisture is plentiful.
Iris may also be chemically controlled with spot applications of 2,4-D. Application rate should be 2-4 lbs ae 2,4-D per 100 gallons of water. Applications should be made when iris is in early bloom. These Iris spp. have a thick waxy cuticle and thorough wetting of the foliage is critical for control. 2,4-D may injure or kill broadleaf plants it contacts. Therefore spot applications directly to individual plants may improve selectivity.
There has also been some research that indicated removing grazing for three years may effectively reduce iris populations to normal levels, with or without herbicide use. This type of passive management strategy may depend upon environmental conditions and the vegetational composition of the meadow. No details of these factors were reported, and the underlying reasons for the iris reductions are uncertain.

Eckert, RE J., Bruner, A. D., Klomp, G. J., and Peterson, F. F. 1973. Control of Rocky Mountain iris and vegetation response on mountain meadows. Journal of Range Management 26:352-355.
Fuller, T. C.and McClintock, E. 1986. Poisonous plants of California. Berkeley, CA: University of California Press.
Hickman, J. C. 1993. The Jepson Manual. Higher Plants of California. Berkeley, CA: University of California Press.
Pryor, M. R. and Talbert, R. E. 1958. Iris missouriensis: a serious weed pest. The Bulletin Dept.of Agric., State of Calif.XLVII 4 pp.:
Uno, G. E. 6-1982. Comparative reproductive biology of hermaphroditic and male-sterile Iris douglasiana Herb. (Iridaceae). American Journal of Botany 69:818-823.
Uno, G. E. 1982. The influence of pollinators on the breeding system of Iris douglasiana. American Midland Naturalist 108:149-158.
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