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
SYNONYMS:western blue flag: wild iris
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.
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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and UNDERGROUND STRUCTURES:Rhizomes tuber-like,
creeping, with shallow fibrous roots.
FLOWERS:Parts in 3s. Stigmas flat, scale-like on the underside
of the petal-like style branches.
and SEEDS:Capsules oblong, 3-chambered.
Seeds numerous, vertically compressed, in 1 or 2 rows in each chamber.
PROPAGATION/PHENOLOGY:Reproduce vegetatively from rhizomes and by seed. Leaves
die back during periods of drought or below freezing tempertatures.
disturbance aids survival of other native species and helps keep iris populations
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