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slender blue iris

iris family

Habit Herbs, perennial, rarely annual [or shrubs with woody caudex], evergreen or seasonal, sometimes cespitose; rootstock a rhizome, bulb, or corm.
Rhizomes

superficial or only slightly buried in peaty soil, cordlike portions usually 1-branched, 40 cm × 2–5 mm, bearing scalelike leaves at nodes;

nodal roots absent.

Stems

simple or 1–2-branched, 3–8 dm.

Flowering stems

aerial (or subterranean in Romulea), simple or branched, terete or variously compressed, angled or winged.

Leaves

basal with blade slightly ribbed, 3–6 dm × 0.2–0.5 cm;

cauline 1–4, erect.

basal and cauline, distichous;

proximal 2–3 sometimes membranous, not reaching much above ground;

others with open or closed sheaths, usually unifacial [bifacial or terete], oriented edgewise to the stem;

blade parallel-veined, plane or pleated, channeled.

Inflorescences/Inflorescence units

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

spathes pale brown, narrowly lanceolate, 2–4 cm, scarious or partially membranaceous.

umbellate, monochasial cymes (rhipidia), spikes, or solitary flowers;

rhipidia enclosed in 2, opposed, usually large, leafy to dry bracts (spathes);

flowers except for the first subtended by 1 floral bract;

spike flowers each subtended by 2, opposed bracts.

Flowers

perianth pale blue or blue-violet;

floral tube 0.2–0.3 cm;

sepals pale violet, veined deep violet basally, ovate, 4–5 × 1.3–2 cm, base abruptly attenuate;

petals lavender, oblanceolate, 3.5–4.5 × 0.7–1.5 cm;

ovary trigonal, sharply angled;

style arched, narrow, 2–3 cm, crests divergent, quadrate, 0.5–0.7 cm, margins serrate;

stigmas sharply triangular;

pedicel somewhat flattened, 3–7 cm, exserted from spathe.

usually pedicellate [± sessile];

perianth actinomorphic or zygomorphic, petaloid, with 2 equal or unequal whorls of 3 tepals each [1 whorl of 6];

tepals usually large, showy, distinct or connate in tube;

stamens 3 [2], inserted at base of outer tepals or in tube, symmetrically arranged or unilateral, arcuate [declinate];

filaments distinct or partly to completely connate, sometimes weak, unable to support anthers;

anthers with 2 pollen sacs, extrorse, occasionally latrorse, usually dehiscing longitudinally [rarely apically];

ovary inferior [superior in Tasmanian Isophysis], 3-locular [1-locular];

placentation axile [parietal];

ovules 2–few, anatropous;

style single, filiform at least proximally, usually 3-branched or 3-lobed, branches either filiform, distally expanded, sometimes each divided in distal 1/2, stigmatic toward apices, or branches thickened, or flattened, petaloid, stigmas then abaxial below apices.

Fruits

capsular, loculicidal, rarely indehiscent, firm to cartilaginous, occasionally woody.

Capsules

sharply 3-angled, almost winged, 3–4 × 1.2–1.4 cm, concave faces 6–14 mm wide.

Seeds

in 1 row per locule, buff to dark brown, pyriform, with convex sides, 3–4 mm, smooth.

globose to angular (prismatic) or discoid, sometimes broadly winged;

seed coat usually dry (rarely fleshy);

endosperm hard, with reserves of hemicellulose, oil, and protein;

embryo small.

2n

= 42.

Iris prismatica

Iridaceae

Phenology Flowering Apr–Jul.
Habitat Swampy, peaty soil
Distribution
from FNA
AL; CT; DE; GA; KY; MA; MD; ME; NC; NH; NJ; NY; RI; SC; TN; VA
[WildflowerSearch map]
[BONAP county map]
Nearly worldwide but rare in tropical lowlands; best represented in southern Africa
[BONAP county map]
Discussion

Genera ca. 65, species ca. 1810 (16 genera, 92 species; 9 genera, 19 species introduced, and various hybrid complexes in the flora).

Iridaceae are currently divided into four subfamilies (P. Goldblatt 1990, 1991). Subfamily Isophysidoideae Takhtajan is monotypic, comprising the Tasmanian Isophysis T. Moore with a superior ovary. Only subfamily Iridoideae is native in North America. The remaining Nivenioideae Schulze ex Goldblatt and Ixioideae Klatt are centered in Africa south of the Sahara. Iridaceae are of considerable economic importance in ornamental horticulture and the cut-flower industry, especially Iris, Gladiolus, and Freesia. Several other genera (e.g., Crocus, Dietes, Sparaxis, Tritonia, Watsonia) are cultivated in gardens in both tropical and temperate areas. Moraea and Homeria are poisonous and pose significant problems in cattle- and sheep-raising areas, notably in southern Africa.

In addition to the several genera and species escaped from cultivation and dealt with in detail below, the following are widely grown in areas of mild winter and may persist in and near abandoned gardens, sometimes reproducing successfully: Dietes Salisbury [D. iridioides (Linnaeus) Salisbury ex Klatt, D. grandiflora N. E. Brown]; Ixia Linnaeus (I. maculata Linnaeus, I. polystachya Linnaeus); Crocus cultivars and even some wild species.

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

Key
1. Inflorescences spicate, 2–many-flowered, or flowers solitary and sessile, each subtended by pair of opposed bracts; rootstock a corm; flowers actinomorphic or zygomorphic; tepals tubular-connate.
→ 2
1. Inflorescences rhipidiate, (1–)2–several-flowered; spathes 2, paired, opposed, often leafy; rootstock a rhizome, bulb, or indistinct; flowers actinomorphic, tepals distinct or tubular-connate.
→ 8
2. Flowers solitary on aerial axes; leaves all inserted below ground; blade filiform, oval to terete in cross section, with 4 longitudinal grooves.
Romulea
2. Flowers in 2–many-flowered spikes; leaves some at least inserted above ground level; blade usually expanded, plane (rarely linear, cruciform in cross section).
→ 3
3. Flowers actinomorphic, upright; bracts scarious, translucent, with brown streaking; perianth tube shorter than limb.
Sparaxis
3. Flowers zygomorphic, upright or facing side; bracts not scarious; perianth tube shorter or longer than limb.
→ 4
4. Style branches each divided for about 1/2 its length, filiform throughout.
→ 5
4. Style branches each simple or apically notched, filiform throughout or expanded terminally.
→ 6
5. Spikes inflexed, ± horizontal, flowers secund; seeds globose, without wings.
Freesia
5. Spikes erect, flowers distichous; seeds angular, 1–2-winged.
Watsonia
6. Tepals variously colored; style branches expanded terminally, not filiform throughout; seeds usually broadly winged, globose or angular.
Gladiolus
6. Tepals shades of orange to reddish; style branches apically notched, not expanded above; seeds not winged, globose.
→ 7
7. Perianth tube obliquely funnel-shaped; tepals subequal (dorsal only slightly larger).
Crocosmia
7. Perianth tube narrow and cylindric proximally, abruptly widened and broadly cylindric distally; dorsal tepal ± 2 times others.
Chasmanthe
8. Leaves plicate, occasionally so narrow that pleats are obscure; rootstock a bulb with brown, dry tunics.
→ 9
8. Leaves plane; rootstock a rhizome or indistinct.
→ 12
9. Tepals unequal, inner whorl less than 1/2 outer.
Herbertia
9. Tepals subequal or inner whorl only slightly smaller than outer.
→ 10
10. Style eccentric and recurving; style branches fairly short, undivided, ascending.
Calydorea
10. Style straight, central; style branches each deeply divided into filiform arms.
→ 11
11. Style branches divided for 1/2 their length, rarely more; style arms arching over or between anthers; anthers pandurate.
Alophia
11. Style branches divided almost to base; style arms extending horizontally between anthers; anthers linear-oblong.
Nemastylis
12. Style branches broad, petaloid, terminating in paired crests; anthers appressed to style branches.
Iris
12. Style branches not broad or petaloid; anthers not appressed to style branches.
→ 13
13. Filaments distinct; style branches flattened, relatively short, not extending between stamens.
Belamcanda
13. Filaments partly connate; style branches filiform, relatively short or long, extending between stamens.
→ 14
14. Tepals white or yellow, spreading from base; style branches relatively long, extending between stamens below anthers.
→ 15
14. Tepals blue, purple, pink, or white; style branches relatively short, extending between anthers.
→ 16
15. Tepals white, inner exceeding outer.
Libertia
15. Tepals yellow, inner ± equaling to slightly smaller than outer.
Sisyrinchium
16. Leaves centric, somewhat inflated; stem simple; seeds brown, angular.
Olsynium
16. Leaves plane; stem simple or branched; seeds blackish, globose, with broad concave indentation in chalazal area.
Sisyrinchium
Source FNA vol. 26, p. 395. FNA vol. 26, p. 348. Author: Peter Goldblatt.
Parent taxa Iridaceae > Iris > subg. Limniris > sect. Limniris > ser. Prisimaticae
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. missouriensis, I. munzii, I. orientalis, I. pallida, 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
Subordinate taxa
Alophia, Belamcanda, Calydorea, Chasmanthe, Crocosmia, Freesia, Gladiolus, Herbertia, Iris, Libertia, Nemastylis, Olsynium, Romulea, Sisyrinchium, Sparaxis, Watsonia
Name authority Pursh: Fl. Amer. Sept. 1: 30. (1814) Jussieu
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