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giant blue iris

sweet iris

Rhizomes

green, extensively branched, forming large clumps, 2–4 cm diam., with pale leaf scars.

branching, forming extensive clumps, 1.5–2 cm diam., smooth except for narrow leaf scars that completely encircle rhizome.

Stems

2–3-branched, solid, 10–15(–20+) dm.

1–3-branched, 6–10 dm.

Leaves

basal 4–6, erect, blade bright green, ensiform, 10–13 dm × 2–3 cm, apex slightly curved;

cauline with blade foliaceous, appearing as elongated spathe, 5–6.5 dm × 2–3 cm, not exceeding flowers.

erect to spreading, blade green (some forms with white or yellow longitudinal stripes), ensiform, 3–6 dm × 3–4 cm, very glaucous, smooth.

Inflorescences/Inflorescence units

2–3-flowered, branch units 1–2-flowered;

spathes tightly enclosing ovary and pedicel, 15–20 cm, subequal;

outer narrowly lanceolate, keeled, margins pale, narrow, inner margins translucent, broad, scarious.

with terminal unit 3-flowered, branch units 2–3-flowered;

distal branches subtended by scarious bracts, lower one to 15 cm, herbaceous, green;

spathes completely silvery white, 2–3.5 cm, scarious.

Flowers

perianth blue or blue-purple;

floral tube tubular-prismatic, 9-ribbed and -grooved, 4–5 cm;

sepals blue or blue-purple with white streaks surrounding signal, oval to orbicular-oval, 9.5–11 × 4–5 cm, base abruptly attenuate into claw, apex obtusely angled, signal with raised, yellow, pubescent central ridge, claw green, striate, 4–4.5 × 1–1.2 cm;

petals erect or spreading-erect, spatulate, 7–8.5 × 2–3 cm, base cuneate, apex emarginate;

ovary bluntly 6-angled, 4–4.5 cm;

style blue-violet, keeled, 3.5–4 cm, raised above sepals, crests recurved, 1.5–2 cm, margins sharply and irregularly serrate;

stigmas 2-lobed with 2 triangular teeth;

pedicel columnar, 3.5–5 cm.

often very fragrant;

perianth light blue-violet to mauve-purple, one form with blue pigment limited as stipples or stitches along margin and/or along veins, with ground color white on both petals and sepals;

floral tube 1–1.3 cm;

sepals slightly reflexed, obovate, 7.8–8.3 × 5–5.3 cm, with wedge-shaped claw marked with brown veins, beard yellow with white tips;

petals blue-violet, in some forms lighter than sepals, with some brown veining at base and on claw, obovate, 8 × 5 cm;

ovary trigonal, 6-grooved, 1–1.5 cm;

style violet, fading paler along margins, keeled along midrib, 2–2.4 × 1 cm, crests rounded, 1.4 cm, apex acute;

stigmas rounded, margins entire;

pedicel very short, 2–3 mm.

Capsules

drooping, bright green, ellipsoid, hexagonal in cross section, with 6 broad, rounded lobes, 8–10 × 3 cm, indehiscent;

after anthesis, flower stem elongates, arching downward to push capsule into water, where walls are broken down and as funiculus is broken, seed rises to surface.

borne on ends of stems and branches, oblong, trigonal, 6-grooved, 4–5 × 1.5–2 cm.

Seeds

in 2 rows per locule, brown, D-shaped, 8–10 mm wide, very corky.

in 2 rows per locule, dark brown, compressed, cubical, wrinkled.

2n

= 44.

= 24.

Iris giganticaerulea

Iris pallida

Phenology Flowering Mar–Apr. Flowering Apr–mid Jun.
Habitat Shallow water or very wet roadside ditches Widely cultivated and often persisting around old dwellings
Distribution
from FNA
AL; LA; MS
[WildflowerSearch map]
[BONAP county map]
from FNA
CA; GA; IN; MO; Europe [Introduced in North America]
[BONAP county map]
Discussion

Iris pallida is considered to be one of the parents of I. germanica, to which it contributed blue pigment (delphinin) as well as the recessive white allele responsible for white-flowered forms. It also contributed the recessive distribution-pattern allele that limits the blue pigment to veins and to stipples or larger dots along the margins of the petals and sepals, the plicata pattern so popular in the garden today.

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

Source FNA vol. 26. FNA vol. 26, p. 376.
Parent taxa Iridaceae > Iris > subg. Limniris > sect. Limniris > ser. Hexagonae Iridaceae > Iris > subg. Iris
Sibling taxa
I. bracteata, I. brevicaulis, I. chrysophylla, I. cristata, I. douglasiana, I. fernaldii, I. fulva, I. germanica, I. hartwegii, I. hexagona, I. hookeri, 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
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. missouriensis, I. munzii, I. orientalis, 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. elephantina, I. hexagona var. giganticaerulea, I. miraculosa
Name authority Small: Addisonia 14: 5, plate 451. (1929) Lamarck: in J. Lamarck et al., Encycl. 3: 294. (1789)
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