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Rocky Mountain iris, western blue flag

beach-head iris, iris de Hooker

Rhizomes

freely branching, producing large colonies, stout, 2–3 cm diam., clothed with dark remnants of old leaves;

roots fleshy.

many-branched, forming dense, cespitose clumps with many crowded fans with persistent old leaf bases, 3–5 × 1.3–1.5 cm.

Stems

simple or 1–2-branched, solid, 2.5–6 dm.

several to many from a single clump of fans, simple, 0.5–6 dm.

Leaves

basal with blade light green, often white basally, not prominently veined, linear, 4.5–6 dm × 0.3–1.2 cm, glaucous, apex acute;

cauline 2–3, often shed with spent stem, similar to basal leaves, distal may subtend branch.

basal erect or strongly ascending, blade 1–5.2 dm × 0.5–1.4 cm;

cauline 2–4, proximal 2–3 similar to basal leaves, distalmost leaf occasionally borne nearly midway on stem, clasping, blade bracteiform, lanceolate, 0.5–1.5 dm.

Inflorescences/Inflorescence units

with terminal and lateral units (when present) (1–)2–3-flowered;

spathes subopposite to distant, to as much as 3–7.5 cm apart, lanceolate or ovate, keeled, outer usually shorter, 3.5–4 cm, inner 5.5–7 cm, scarious with herbaceous areas basally and along keel, apex acuminate.

1–2-flowered;

spathes herbaceous, lanceolate to oblong-ovate, 2.5–6 cm, firm, outer spathe apex acute, inner similar or scarious at apex.

Flowers

perianth blue to lavender to white, veined deeper violet;

floral tube green with purple veins in line with midrib of petals, funnelform, constricted above ovary, 0.5–1.2 cm;

sepals deeply veined lilac-purple, with yellow-white signal at base of limb, claw yellowish white, veined and dotted with purple, obovate, 3.7–7 × 1.2–3.2 cm;

petals slightly divergent, oblanceolate to spatulate, 3.6–7 × 0.5–1.2 cm, base gradually attenuate, apex acuminate or rarely emarginate;

ovary trigonal with 6 shallow ridges, 1–2 cm;

style 2.4–4 cm, crests quadrate, 0.7–1.4 cm, margins irregularly toothed;

stigmas 2-lobed, margins entire;

pedicel slender, 1–6 cm at anthesis, increasing to 7.5–8 cm at maturity.

perianth deep to pale blue or blue-violet;

floral tube 0.5–0.75 cm;

sepals broadly rounded, 2.5–4 cm wide, base strongly attenuate to claw, signal diffuse white basal patch;

petals much reduced to insignificant, involute or tubular rudiments, 1–2 cm, apex with short bristle, mostly hidden by sepal bases;

ovary green or flushed purple, acutely trigonal;

style white with purple keel, 2–5 cm, crests overlapping, 2-lobed, subquadrate, margins coarsely serrate;

stigmas rounded-triangular, margins entire;

pedicel 2.5–4 cm.

Capsules

almost circular in cross section, with 6 obvious, equidistant ridges, 4–5 × 1.5 cm.

thin walled, trigonal, with rounded angles and grooved sides, 2–4 cm, apex blunt.

Seeds

light brown, nearly globular to pyriform, 4–4.5 mm, wrinkled.

in 2 rows per locule, dark brown with prominent white raphe, compressed-pyriform, 4–6 mm, lustrous.

2n

= 38.

= 38.

Iris missouriensis

Iris hookeri

Phenology Flowering May–Jul. Flowering Jun–Jul.
Habitat Wet meadows, roadside ditches, margins of streams Grassy headlands, upper borders of beaches, dunes, and other coast formations, within reach of ocean spray
Elevation 10–3000 m (0–9800 ft)
Distribution
from FNA
AZ; CA; CO; ID; MT; NE; NM; NV; OR; SD; UT; WA; WY; AB; BC; n Mexico
[WildflowerSearch map]
[BONAP county map]
from FNA
ME; NB; NL; NS; PE; QC
[BONAP county map]
Discussion

The ecological range of Iris missouriensis is probably more varied than that of any other North American species of the genus, extending from almost sea level in southern California to 3000 m in Montana and Wyoming. There is correspondingly wide variation in a number of characters, which has caused much confusion as to taxonomic circumscription. Homer Metcalf (pers. comm.) made a detailed study of this species. The basic requirement for its success seems to be an extremely wet area before flowering and then almost desertlike conditions for the rest of the summer.

In large populations, sometimes covering hundreds of acres, Iris missouriensis may be found with either simple or branched stems, leaves from 4 mm to more than 1 cm wide, shorter than the stem or longer, only one flower to as many as three on a stem, and colors from deep blue to almost pure white. A single plant found on the Pariah Plateau in Kane County, Utah, with leaves only 3–4 mm wide and a single flower stem only 4 cm long, which meant that the flower was at almost ground level, was named Iris pariensis. No other such specimen has been located, and this entity must be considered as just an aberrant form that was due to the desertlike conditions in which it was growing.

Iris missouriensis is known to hybridize with I. longipetala.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Some authors still treat this taxon as Iris setosa var. canadensis, but others believe that it merits recognition as a separate species. I have seen I. hookeri flowering in its native habitat in both Nova Scotia and Prince Edward Island, and have examined dozens of herbarium specimens of both it and I. setosa, from which it is clearly distinct.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Source FNA vol. 26, p. 388. FNA vol. 26, p. 381.
Parent taxa Iridaceae > Iris > subg. Limniris > sect. Limniris > ser. Longipetalae Iridaceae > Iris > subg. Limniris > sect. Limniris > ser. Tripetalae
Sibling taxa
I. bracteata, I. brevicaulis, I. chrysophylla, I. cristata, I. douglasiana, I. fernaldii, I. fulva, I. germanica, I. giganticaerulea, I. hartwegii, I. hexagona, I. hookeri, I. innominata, I. lacustris, I. longipetala, I. macrosiphon, I. munzii, I. orientalis, I. pallida, I. prismatica, I. pseudacorus, I. pumila, I. purdyi, I. savannarum, I. setosa, I. sibirica, I. tenax, I. tenuis, I. tenuissima, I. tridentata, I. verna, I. versicolor, I. virginica
I. bracteata, I. brevicaulis, I. chrysophylla, I. cristata, I. douglasiana, I. fernaldii, I. fulva, I. germanica, I. giganticaerulea, I. hartwegii, I. hexagona, I. innominata, I. lacustris, I. longipetala, I. macrosiphon, I. missouriensis, I. munzii, I. orientalis, I. pallida, I. prismatica, I. pseudacorus, I. pumila, I. purdyi, I. savannarum, I. setosa, I. sibirica, I. tenax, I. tenuis, I. tenuissima, I. tridentata, I. verna, I. versicolor, I. virginica
Synonyms I. arizonica, I. longipetala var. montana, I. montana, I. pariensis, I. pelogonus, I. tolmieana I. canadensis, I. setosa var. canadensis, I. setosa subsp. pygmaea
Name authority Nuttall: J. Acad. Nat. Sci. Philadelphia 7: 58. (1834) Penny ex G. Don: in J. C. Loudon, Hort. Brit. ed. 2, 591. (1832)
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