Flora of North America species comparison

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Yucca elata

Yucca flaccida

palmella, soap-tree yucca, soap-weed yucca

Adam's needle, beargrass, weak-leaf yucca
Habit Plants solitary or forming small colonies of rosettes, caulescent or rarely acaulescent, distinctly arborescent, mostly few-branched, 1.2–4.5 m; rosettes usually large, symmetrical or asymmetrical. Plants cespitose, forming small colonies, erect, acaulescent or rarely short-caulescent, 1–3 m; rosettes usually small, slowly dying after flowering.
Stems

1–7 per colony, erect, thick, 1–1.5(–2.5) m. Leaf blade pale green, linear, widest near middle, 25–95 × 0.2–1.3 cm, flexible, margins entire, curled, filiferous, whitish, apex tapering to short spine.

simple, to 0.3 m. Leaf blade erect, proximal leaves becoming reflexed at middle in age, lanceolate, gradually tapering to apex, thin, widest near middle, 40–80 × 1–4(–5) cm, rigid or soft and limp, glabrous, margins entire, filiferous, apex spinose.
Inflorescences

mostly paniculate, sometimes distally racemose, arising beyond rosettes, mostly narrowly ovoid to ovoid, 7–15 × 2.5–6.5 dm;

branches 0.7–3.5 dm;

bracts erect;

peduncle sometimes scapelike, 1–2 m, 2.5–5.5 cm diam.

paniculate, arising beyond rosettes, narrowly ovoid, 4–15 dm, mostly pubescent;

bracts erect, proximal to 25 cm, distal 2–3 cm;

peduncle scapelike, 0.5–2.8 m, 0.5–4 cm diam.
Flowers

pendent;

perianth campanulate or globose;

tepals distinct, creamy white, often tinged green or pink, narrow to broadly elliptic or ovate, 3.2–5.7 × 1.3–3.2 cm;

filaments 1.5–2.5(–3.2) cm, pubescent;

anthers (2–)2.5–4.8 mm;

pistil 2–3.2 × 0.6–1 cm;

style white or pale green, 6–11 mm;

stigmas lobed.

pendent;

tepals distinct, white, creamy white, or light greenish white, lanceolate to elliptic, 3–5 × 1–3 cm, mostly pubescent, apex obtuse;

filaments 1.2–2.2 cm;

pistil 1.5–3.8 cm;

ovary pale green, 1.5 cm;

style greenish white to white, papillate;

stigmas lobed;

pedicel 1.5–3 cm.
Fruits

erect, capsular, dehiscent, oblong-cylindric, symmetrical or rarely constricted, 4–8.2 × 2–4 cm, dehiscence septicidal.

erect, capsular, dehiscent, oblong, obpyriform, or conical, 3.5–4 × 1.5–2 cm, dehiscence septicidal.
Seeds

dull black, thin, 7–11(–14) mm diam.

dull black, thin, 6–8 × 5–6 mm.

Yucca elata

Yucca flaccida
Phenology Flowering spring.
Habitat Sand pine-scrub oak, mixed pine-hardwood woodlands, old fields, coastal sands, open or semiopen sites and pine plantations
Distribution
from USDA
North America; Mexico
[WildflowerSearch map]
[BONAP county map]
from FNA
AL; AR; FL; GA; IL; IN; KS; LA; MD; MI; MO; MS; NC; OH; OK; PA; SC; TN; TX; WI; ON
[WildflowerSearch map]
[BONAP county map]
Discussion

Varieties 2 (2 in the flora).

J. L. Reveal (1977c) reduced S. D. McKelvey’s (1938–1947) Yucca utahensis and Y. verdiensis to varieties of Y. elata based primarily u!pon growth forms. J. M. Webber (1953) considered that these taxa are populations of hybrids between members of the Y. glauca alliance of the Great Plains and Y. elata of the American Southwest. Reveal believed that Webber did not provide adequate justification for his hybrid hypothesis. K. H. Clary (1997, pers. comm.) believes that Y. utahensis is genetically distinct from Y. elata and Y. verdiensis, based on DNA evidence and the morphological characters of style, stigma, fruit, and leaf. Her DNA evidence shows that Y. elata and Y. verdiensis are sister taxa, while Y. utahensis is not. Although there is a great range of variation within Y. elata as circumscribed here, the two varieties recognized are difficult to distinguish.

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

Perhaps Yucca flaccida should be considered a variety of Y. filamentosa. The morphological differences are minor. The former has thinner, narrower leaves, and smaller, narrower flowers 4–5 cm long, whereas Y. filamentosa has thick, rigid leaves and flowers 5–7 cm long. Yucca freemanii was described from plants growing in northeastern Texas and southwestern Arkansas. These plants were reported to be glabrous, but some plants that are otherwise attributable to Y. freemanii are mostly pubescent through the infloresecence, and overall they fall within the variation range of Y. flaccida. Yucca flaccida is cultivated in some of the northern states and Canada, where it sometimes has naturalized.

The results of DNA studies by K. H. Clary (1997) are incongruent with our treatment of Yucca flaccida, which warrants further research. It is the only dry-fruited species that groups with the fleshy-fruited ones in Clary’s consensus tree, where Y. flaccida and Y. filamentosa are quite distant. DNA variation indicates that Y. louisianensis is genetically distinct and more closely related to Y. filamentosa than to Y. flaccida.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Key
1. Capsules 5–8.2 cm; pistil 2.8–3.2 cm; leaf blade 30–95 cm.
var. elata
1. Capsules 4–4.5 cm; pistil 2–2.5 cm; leaf blade 25–45 cm.
var. verdiensis
Source FNA vol. 26, p. 432. FNA vol. 26, p. 433.
Parent taxa Agavaceae > Yucca Agavaceae > Yucca
Sibling taxa
Y. aloifolia, Y. angustissima, Y. arkansana, Y. baccata, Y. baileyi, Y. brevifolia, Y. campestris, Y. constricta, Y. faxoniana, Y. filamentosa, Y. flaccida, Y. glauca, Y. gloriosa, Y. harrimaniae, Y. intermedia, Y. madrensis, Y. necopina, Y. neomexicana, Y. pallida, Y. reverchonii, Y. rostrata, Y. rupicola, Y. schidigera, Y. tenuistyla, Y. thompsoniana, Y. treculeana, Y. utahensis
Y. aloifolia, Y. angustissima, Y. arkansana, Y. baccata, Y. baileyi, Y. brevifolia, Y. campestris, Y. constricta, Y. elata, Y. faxoniana, Y. filamentosa, Y. glauca, Y. gloriosa, Y. harrimaniae, Y. intermedia, Y. madrensis, Y. necopina, Y. neomexicana, Y. pallida, Y. reverchonii, Y. rostrata, Y. rupicola, Y. schidigera, Y. tenuistyla, Y. thompsoniana, Y. treculeana, Y. utahensis
Subordinate taxa
Y. elata var. elata, Y. elata var. verdiensis
Synonyms Y. concava, Y. filamentosa var. concava, Y. filamentosa var. flaccida, Y. filamentosa var. glaucescens, Y. filamentosa var. puberula, Y. filamentosa var. smalliana, Y. flaccida var. glaucescens, Y. flaccida var. major, Y. freemanii, Y. glaucescens, Y. louisianensis, Y. orchioides var. major, Y. puberula, Y. smalliana
Name authority Engelmann: Bot. Gaz. 7: 17. (1882) Haworth: Suppl. Pl. Succ., 34. (1819)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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