3530 



YUCCA 



YUCCA 



is the common Adam's needle, Y. flaccida. This 

 persists for years, sending up a tall panicle of cream- 

 white flowers in late spring or early summer. All 

 yuccas are suited to bold and formal effects in garden- 

 ing; as tub specimens they may be used effectively in 

 subtropical bedding or massing. 



Most yuccas may be fertilized if fresh pollen is trans- 

 ferred directly from the anther to the stigmatic cavity 



of a newly opened 

 flower, preferably 

 one seated directly 

 on the main shaft, 

 where nutrition is 

 more certain. Y. 

 aloifolia commonly 

 fruits freely, but 

 the others rarely 

 fruit spontane- 

 ously in cultiva- 

 tion except Y. fila- 

 mentosa and Y. 

 flaccida, which are 

 pollinated by the 

 small white moth 

 (Pronuba yucca- 

 sella) that accom- 

 panies them when 

 cultivated in the 

 western states, but 

 emerges from the 

 pupa too late to 

 pollinate Y. glauca 

 and disappears top 

 early for Y. glori- 

 osa. See Rep. Mo. 

 Bot. Card. 3:99; 



4020. Yucca radiosa. 4 . : 181 > f r addi ' 



tional discussion. 



The great yuccas, or "yucca palms," of southern 

 California are chiefly Y. arborescens. They grow in the 

 higher lands bordering the Mojave and adjacent 

 deserts, reaching a height of 15 to 20 feet. The old 

 plants are exceedingly weird and picturesque. Occa- 

 sionally this species is transferred to gardens, but it is 

 apparently not in the trade. This "Joshua tree" is now 

 separated as Clistoyucca arborescens, Trelease; as it is 

 not in cultivation, it need not be discussed further here 

 except to say that Clistoyucca differs from Yucca 

 in its very short style, fleshy incurved perianth, and 

 spongy dry indehiscent fruit. 



A. Los. not toothed, with fine marginal threads: fr. 



capsular. 



B. Style swollen, green. 



1. gla&ca, Nutt. (Y. angustifolia, Pursh.). Fig. 4019. 

 Acaulescent or with prostrate trunk: Ivs. narrow, 

 24-Hin. wide, gray-green, narrowly white-margined: 

 infl. 3-6 ft. high, rarely branched: fls. greenish white. 

 S. D. to N. Mex. B.M. 2236. F.E. 14, p. 34. G.F. 2: 



247 (adapted in Fig. 4019). Rep. Mo. Bot. Card. 3:8, 

 51; 13:23-25, 83. Gn. 76, p. 402. G.W. 10, pp. 83, 

 214. A distinctly caulescent erect form with larger 

 branched infl. is var. stricta, Trel. (Y. stricta, Sims). 

 B.M. 2222. Gn. 8, p. 130. Rep. Mo. Bot. Card. 

 13:26, 27. 



BB. Style oblong, white. 



2. radiosa, Trel. (Y. angustifolia radiosa, Engelm. 

 Y. angustifolia eldta, Engelm. Y. elata, Engelm.). 

 Fig. 4020. Short-trunked or up to 15-20 ft. high: Ivs. 

 M~K m - wide, gray-green, narrowly white-margined: 

 infl. panicled, long-stalked: fls. white. S. Ariz., W. 

 Texas, and Mex. G.F. 2:569 (adapted in Fig. 4020). 

 B.M. 7650. S.S. 10:504. Rep. Mo. Bot. Gard. 3:9; 

 4:10, 15, 22; 13:21, 22, 83, 86. 



3. filamentosa, Linn. ADAM'S NEEDLE. Figs. 4021, 

 4022. Acaulescent: Ivs. 1 in. wide, scarcely glaucous, 

 with curly threads: infl. long-stalked, 412 ft. high, 

 usually glabrous: fls. nearly white: carpels with rounded 

 backs. S. C. to Miss, and Fla. B.M. 900. Redoute, 

 Lil. 5:277, 278. Mordaunt, Herb. Gen. 4:258. Rep. 

 Mo. Bot. Gard. 13:8-12, 83. G.C. III. 57:187. G. 34: 

 605. A variegated form is f. variegata, and a form 

 with broad stiff spoon-like Ivs. is var. concava, Baker 

 (Y. concava, Haw.). Rep. Mo. Bot. Gard. 13:10, 83. 



4. flaccida, Haw. Differs from the preceding, for 

 which it is commonly grown, in its more flaccid recurv- 

 ing Ivs. with slenderer straighter threads, and carpels 

 with angular backs. N. C. to Ala. Gn. 58, p. 447; 

 78, p. 433. Rep. Mo. Bot. Gard. 13:12-17, 83. A 

 distinctly glaucous form, much cult, as Y. filamentosa, 

 is var. glaucescens, Trel. (Y. glaucescens, Haw.). B.M. 

 6316 (as Y. orchioides var. major). Ref. Bot. 324. Rep. 

 Mo. Bot. Gard. 3:10; 13:12-15, 17, 83. A transiently 

 variegated form of this is f . lineata. 



4021. Adam's needle. Yucca filamentosa. (From a plant 

 4 feet high) 



