YAM. See Pio-^icorea and Siveet Potato. CircTili 

 Piv. ot' Bot., U. S. Dept. Aijrif., bus vahialtK- fu 

 note^ Mil the introduction ot" West hulian Vnu\s { 

 eoreas) to subtropical a,L;rii.'ulture in tlit- U. ^, 



YARKOW. Consult Achillea. 



YATE. See Encahji't'iA ,>,■<■!, Im/ah's. 



YELLOW ROOT SHRUB. Xa nlhorrhiia . 



YELLOW-WOOD. ChtJra.^ti.< ti>ict<>rla. 



YERBA BUENA. .Uicroni,-ri>i Doiiglasii. 



YEW. See Taxu.^. 



YOUTH-ANL-OLD-AGE. Zinnia. 



ir '21. its forms, and glanca are hardy in thit northern states, 

 Ituval and Y. Tn-rn lea )ia shows cnnsiderahle resistance to 

 l>ios- frost. Tho tender species are kept in the cactus house. 

 Well-drained sandy loam suits them best, Imt with pind 

 drainaLre they are tolerant of a lare:e ran^^e nl' soil and 

 exposure. Prop, by seeds, ot^-'sets, stem - em tiii;;s, and 

 the rhizomes that several sprcies in-ddinT, which may 

 be cut into short lengths and i-Motcil in tin- cutting'- bench. 

 y. Trecaleniai blooms usually in March in plant houses, 

 as when wild, and the Mexican species when bron^ht to 

 flower are usually sprinLrliloomers. but they nften refuse 

 to flower for hoiL: p'-rii>ds and tlu-ii suibli-uly and unex- 

 pectedly pr<Mluce an aliunilam-e of simultaneous bloom. 

 even on the smaller ]dants. Ttt the luirdy species, 

 I', (ila)ica flowers in June and it is quickly followed 

 by JT. filariieiifo.'^a and 1'. fla<-rif],i , while the fr.rms of 

 Y. gloriosa, which usually f!owt-r only at intiu'vals of 

 several years. Vdoimi fritni bite _\uu:ust to su late iu the 

 autumn as to be cut ilowu bv fro.->t. 





•^iiii^''"' 



2761. Yucca 'Whipplei. 



yiJCCA (Indian 'narar- for the Manihot, erroneously 

 applied br Gerarde). Lilinr,-,, . Aliout a dozen species. 

 chieflT of' the arid Xorth Anieriean tahle-land and eon- 

 fined to the United fc^tates. Mexicn and adjacent i.slands. 

 Ever£creen,s with lont;. narrow, nsually spiny-pomted 

 leaves and panirles of laru'e white no.-turnal flowers 

 freouenth- shaded with ereen or purple. 



Y. fihnnriitox/i. fificriiln. burojta, gloriosa m some of 



Most species niav he fertilized if fresh pollen is trans- 

 ferred directly from the anther to the stigmatic cayity of 

 a newly opened tlower, preferably one seated directly on 

 the main shaft, where nutrition is more certain, Y. <i loi- 

 foliii commonly fruits freely, but the others rarely fruit 

 spontaneously' in cultivation except Y. fihnm-iitnso and 

 Y. fliiceida. which are |iollinaTcd by a small wlnfe m.itli 

 {Proittibu ijiiccu.Sfll'i ) that accompanies them \vUeu cul- 



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(1999) 



