Yucca angustissima |
Yucca arkansana |
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fineleaf yucca, narrowleaf yucca |
Arkansas yucca |
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Habit | Plants solitary or forming small to large colonies of rosettes, acaulescent or rarely caulescent, to 3 m diam.; rosettes usually small. | Plants forming small colonies, acaulescent or caulescent; rosettes usually small. | ||||||||||||
Stems | procumbent, 0.1–0.4 m, or erect, 1–2 m. Leaf blade rigidly spreading, including distal leaves, linear, lanceolate, concavo-convex, or plano-keeled, widest near middle, 20–80(–150) × 0.4–2 cm, rigid or flexible, not glaucous, margins entire, becoming filiferous, white, becoming brownish, gray, or green, apex long-acuminate, spinose, spine acicular, short, 3–7 mm. |
decumbent, short, to 0.2 m. Leaf blade mostly yellowish green, flattened, grasslike, concavo-convex, widest near middle, 20–60(–70) × 0.7–2(–2.5) cm, flexible, margins entire, curled, filiferous, apex long, tapering to short spines 1.6–3.2 mm. |
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Inflorescences | racemose, occasionally paniculate proximally, arising well beyond rosettes, (4–)8–20 dm, glabrous or finely pubescent; branches, when present, 0.5–1 dm; bracts erect, linear, proximal 10–20 × 1–2 cm, distal 3–8 × 1–2 cm; peduncle scapelike, 0.3–2.5 m, 1–2 cm diam. |
racemose, occasionally paniculate proximally, arising within rosettes or at rosette level, 3–6(–8) dm, glabrous; bracts erect; peduncle scapelike, 0.2–0.5(–0.6) m, 0.3–0.7(–1.3) cm diam. |
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Flowers | pendent, 3–5.5(–6.5) cm; perianth campanulate to globose; tepals distinct, white to cream or greenish white, often tinged pink or brown, broad to narrowly elliptic to lanceolate-elliptic or orbiculate, 3–6.5 × 1.3–2.5 cm; filaments 0.7–2.8 cm; anthers 3.2–6 mm; pistil 1.5–3.5 cm; style white to pale green, 3–10(–13) mm; stigmas lobed. |
pendent; perianth globose; tepals distinct, greenish white, elliptic to orbicular or oblong, 3.2–6.5 × 2–5 cm; filaments 1.3–2.5 cm; anthers 3.2 mm; pistil 2.5–2.8(–3.2) cm; style dark green, 7–13 mm, tumid; stigmas lobed. |
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Fruits | erect, capsular, dehiscent, moderately to deeply constricted, 3.5–7.5 × 2–3 cm, dehiscence septicidal. |
erect, capsular, dehiscent, oblong-cylindric to obovoid, constricted near middle, stout, 4–6.5(–7) × 2–3 cm, dehiscence septicidal. |
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Seeds | dull black, thin, 7–9 × 5–7 mm. |
dull black, thin, ca. 1 cm diam. |
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Yucca angustissima |
Yucca arkansana |
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Phenology | Flowering spring. | |||||||||||||
Habitat | Gravelly soil, limestone outcrops, rocky hillsides, prairies | |||||||||||||
Elevation | 100–400 m (300–1300 ft) | |||||||||||||
Distribution |
North America
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AR; KS; MO; OK; TX
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Discussion | Varieties 4 (4 in the flora). Our treatment of Yucca angustissima reflects the concepts of J. L. Reveal (1977c). Each variety is well isolated geographically, but they overlap with one another morphologically. S. L. Welsh et al. (1993) treated the taxa in this complex at species level, with the exception of Y. angustissima var. aria, considered a high-altitude extreme of the typical variety. K. H. Clary (1997) presented DNA evidence that supports Welsh et al.’s treatment of this complex, in that Y. angustissima, Y. kanabensis, and Y. toftiae sort out distinctly from one another in her consensus tree. However, Welsh et al. indicated significant intergradation among these taxa, which makes their recognition at varietal rank seem most appropriate. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Yucca arkansana shows considerable variation, particularly in the eastern part of its range. S. D. McKelvey (1938–1947) described var. paniculata and suggested that it is an eastern extension of the species with a taller, paniculate, and pubescent inflorescence. Yucca arkansana approaches Y. louisianensis, which we have reduced to synonymy under Y. flaccida. K. H. Clary’s (1997) DNA consensus tree places Y. arkansana and Y. louisianensis adjacent to one another. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 26, p. 434. | FNA vol. 26, p. 436. | ||||||||||||
Parent taxa | Agavaceae > Yucca | Agavaceae > Yucca | ||||||||||||
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Subordinate taxa | ||||||||||||||
Synonyms | Y. angustifolia var. mollis, Y. arkansana var. paniculata, Y. glauca var. mollis | |||||||||||||
Name authority | Engelmann ex Trelease: Rep. (Annual) Missouri Bot. Gard. 13: 58, plate 23, fig. 1, plate 24, fig.1, plate 83, fig. 6, plate 93, fig. 1. (1902) | Trelease: Rep. (Annual) Missouri Bot. Gard. 13: 63. (1902) | ||||||||||||
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