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Key to Yucca

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1 Plants caulescent when fully developed (an erect shrub or small tree), the lower parts of the stem readily visible because no longer clothed with leaves.
  2 Leaf margins regularly fraying from the leaf as stiff threads; leaves 3-5 cm wide; fruits pendent berries with soft flesh, 7-14 cm long; [e. TX and westwards]
  2 Leaf margins not fraying from the leaf as stiff threads; leaves 2.5-8 cm wide; fruits pendent or erect berries with leathery or soft flesh, 2.5-11.5 cm long; [collectively widespread, from se. VA south to s. FL, west to s. AZ].
    3 Fruits with soft flesh, 5-11.5 cm long; leaves very stiff; leaf surface dull; leaves persistent only on upper trunk; [c. TX and southwards]
    3 Fruits with leathery or soft flesh, 2.5-8 cm long; leaf surface waxy, shiny; leaves persistent all along trunk; [e. TX and eastwards].
      4 Leaf margins minutely notched-serrulate, particularly toward the base; seeds 2.5 mm thick, marginless
      4 Leaf margins entire, smooth, hyaline-brown or hyaline-yellow; seeds ca. 1 mm thick, margined.
        5 Leaf blades rigid, straight; inflorescences extending beyond rosettes; fruits pendent, 5.5-8 cm long; [of NC south to FL]
        5 Leaf blades (some or all) recurved, flexible; lower portions of inflorescences included within rosettes; fruits generally erect, 2.5-4.5 cm long; [GA and westwards]
1 Plants acaulescent (with a cluster of basal leaves) or with a short stem < 3 dm tall above ground level and clothed with numerous leaves (no part of the aerial stem nonleafy and obviously visible, mostly Yucca constricta).
          6 Leaf margins not fraying from the leaf as stiff threads, minutely notched-serrulate or entire, and hyaline, in shades of yellow, orange, or reddish.
             7 Mature leaves undulate-margined, twisted longitudinally; upper leaf surface strongly concave near its midpoint; [c. TX]
             7 Mature leaves straight-margined, not twisted; upper leaf surface flat or slightly concave near its midpoint (becoming more concave near the tip); [c. and e. TX and w. LA].
               8 Plants solitary; leaves (3-) 3.5-6.5 cm wide; young leaves glaucous becoming olive or yellowish-green with age; inflorescence axes woolly pubescent; inflorescence branches recurved or drooping; [e. TX and w. LA]
               8 Plants solitary or forming of up to 30 rosettes via branching subterranean caudices; leaves 1-3.2 (-4.5) cm wide; mature leaves green or persistently blue-green glaucous; inflorescence axes glabrous or pubescent; inflorescence branches spreading or ascending; [c. and nc. TX or se. TX]
                 9 Plants solitary or forming colonies of 2-10 rosettes; leaves 1-2.5+ cm wide; mature leaves green, with margins reddish-brown and smooth; [coastal se. TX]
                 9 Plants forming colonies of 10-30 rosettes; leaves (1-) 2.5-3.2 (-4.5) cm wide; mature leaves persistently blue-green glaucousolive or yellowish-green, the margins yellowish and minutely dentate; [c. and nc. TX]
          6 Leaf margins entire, usually fraying from the leaf as stiff white, gray, or fulvous (tawny reddish) threads.
                   10 Inflorescence usually unbranched and raceme-like or with 1 or 2 short, spreading branches near base, borne below to just above leaf tips.
                     11 Inflorescences 3-6 (-8) dm, emerging above leaves; leaf blade 0.7-2.5 cm wide, flexible; [more widespread in AR, e. OK, and TX]
                     11 Inflorescences 5-10 dm, usually emerging within leaves; leaf blade 0.8-1.2 cm wide, rigid; [rare in Cross Timbers Region of OK]
                   10 Inflorescence a much-branched panicle, borne well above the tips of leaves.
                       12 Leaves lanceolate or spatulate, or linear-lanceolate, the leaf margins grayish or brownish when fresh with conspicuous marginal threads; [native east of the Mississippi River, occasionally cultivated and escaping westward].
                          13 Inflorescence branches glabrous; leaves 2-6 cm wide, stiff, the apex acute-acuminate to obtuse, often concave upward at the apex, the marginal fibrils usually elongate and intertwining (to 20 cm long); [usually near the coast on sandy soils]
                          13 Inflorescence branches usually scurfy-pubescent or occasionally glabrous; tepals 3-5 cm long; leaves 1.5-4 cm wide, pliable, the apex attenuate-acuminate, not notably concave, the marginal fibrils usually short (to 4 cm long); [more common inland, and on a variety of soil types]
                       12 Leaves linear or linear-spatulate, white-margined when fresh with usually fewer marginal threads or smooth; [native west of the Mississippi River].
                            14 Leaves very slender, 0.8-1.5 cm wide, 100-200 per strikingly globose rosette; fruit usually constricted near middle; [limestone, granite, and clayey substrates]
                            14 Leaves usually 1.5-4 cm wide, ca. 50-85 per rosette (rosette not globose in appearance); fruit constricted or not so; plants of sandy substrates.
                              15 Panicle branches smooth glabrous with glaucous glaze; scape 1-1.8 m. high, slender (4-5 mm. thick at base of inflorescence); leaves relatively wide (to 4 cm), rather soft and limp, relatively few leaves in rosette (10-30); flowering mid-June-July
                              15 Panicle branches glabrous or pubescent but without glaucous haze, rosettes larger (50-85 leaves); scape 1-4 m high (5-10 mm. or more thick at base of inflorescence); leaves various widths but rather rigid and stiff; flowering May-mid-June.
                                16 Inflorescences glabrous; leaves relatively wide, (1.5-) 2-4 cm wide and strongly glaucous; capsules large, to 6 cm long; [endemic to nc. TX]
                                16 Inflorescences pubescent, puberulent, or glabrous; leaves usually narrower, 1-2(-4) cm wide, green or occasionally glaucous; capsules smaller, 2.5-4 cm long (to 6 cm long for rare Y. tenuistyla).
                                  17 Inflorescences usually densely pubescent (rarely glabrous or puberulent); style tumid and greenish, yellowish, or creamy white; leaves 1.5-3 (-4) cm wide; [more widespread west of the Mississippi River]
                                  17 Inflorescence glabrous or puberulent; style oblong, white, and occasionally deeply parted; leaves 1-2 cm wide; [very rare along se. TX coast]