Yucca gloriosa L. (incl. Y. recurvifolia Salisb.) (N-Am.) – A frequent garden plant, increasingly seen as a garden throw-out in ruderal areas or on dumps. More or less to clearly established populations are known since about 2001 from a few locations in coastal dunes, often in or near nature reserves (e.g. Houtsaegherduinen between De Panne and Sint-Idesbald, Fonteintjes between Blankenberge and Zeebrugge, Ter Yde in Oostduinkerke, etc.). In few years’ time and as a result of strong clonal growth Yucca gloriosa has locally built rather impressive populations. On a global scale this species is more widespread than Y. flaccida but it is naturalizing in exactly the same areas: coastal dunes and sandy open soils in the Kempen. In both these areas Y. gloriosa finds climatological and ecological circumstances that roughly agree with those in its area of origin. More than Y. flaccida it is also found in rather numerous additional and widely scattered localities but it then often turns out to be casual or at most seems to persist only temporarily. An up-to-date overview of Belgian records is available here: http://waarnemingen.be/soort/view/126670.
Yucca gloriosa is a taxonomically complex and variable species. Two more or less distinct entities are found in Belgium. Most plants seen are characterized by stiff, rigid leaves and belong to genuine Yucca gloriosa. Plants with more flexible leaves also occur; these are ascribable to Y. recurvifolia Salisb. (syn.: Y. gloriosa var. recurvifolia (Salisb.) Engelm.). Additional studies are needed to clarify their taxonomic status. Hess & Robbins (2002) treat them as mere varieties of a single species while according to Hochstätter (2002) they are best given species rank. Both are separated in the following couplet:
1 Leaf blade erect and rigid, 40-60 mm wide. Inflorescence well extending from rosette leaves. Fruit (berry) pendent, 55-80 mm long === var. gloriosa
Leaf blade flaccid and flexible, recurving, often narrower. Inflorescence hardly extending from rosette leaves. Fruit (berry) erect, 25-45 mm long === var. recurvifolia
Yucca gloriosa develops a distinct stem (in its area of origin up to 5 m tall!), whereas Y. filamentosa is a stemless plant. However, this is only obvious in mature plants.
Molecular studies have shown Yucca gloriosa to be the product of intersectional hybridization between Y. aloifolia L. and Y. filamentosa (Rentsch & Leebens-Mack 2012).
Aymerich P. (2015) Sobre la naturalización de Yucca gloriosa L. en el norte de Cataluña. Bouteloua 20: 16-21. [available online at: http://www.floramontiberica.org/Bouteloua/Bouteloua_20.pdf]
Ferrer-Gallego P.P., Guillot D. & Laguna E. (2015) Tipificación del nombre linneano Yucca gloriosa (Agavaceae). Acta Botanica Malacitana 40: 230-232. [available online at: http://www.biolveg.uma.es/abm/Volumenes/vol40/40_Ferrer-Gallego_et_al_Yu...
Hess W.J. & Laurie Robbins R. (2002). Yucca. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 26. Oxford University Press, New York-Oxford: 423-439. [available online at: http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=135226]
Hochstätter F. (2002) Het geslacht Yucca (Agavaceae). 11. Serie Gloriosae. Succulenta 81(2): 89-95. [available online at: http://www.cactuspro.com/biblio_fichiers/pdf/Succulenta/Succulenta_2002.pdf]
Patil D.A. & Pal R.M. (1987) The floral anatomy of Yucca gloriosa L. (Agavaceae). Indian Sci. Congr. Assoc. Proc. 3: 139-140.
Rentsch J.D. & Leebens-Mack J. (2012) Homoploid hybrid origin of Yucca gloriosa: intersectional hybrid speciation in Yucca (Agavoideae, Asparagaceae). Ecology and Evolution 2(9): 2213-2222. [available online at: https://www.researchgate.net/profile/Jim_Leebens-Mack/publication/233385688_Homoploid_hybrid_origin_of_Yucca_gloriosa_intersectional_hybrid_speciation_in_Yucca_%28Agavoideae_Asparagaceae%29/links/00b7d527433e7692b9000000.pdf]