There has long been confusion about the identification of two arboreal yuccas that grow commonly here in southern California. The more massive of the two, with large swollen basal stems and 12 to 18 inch long light green leaves with a soft tip and small marginal teeth, is considered to be Yucca elephantipes by those most familiar with the plant but has been commonly called Yucca gloriosa in the nursery trade. The other plant which has broader and longer more luxurious glossy leaves and heavy stems without as much basal swelling has also been commonly referred to as Yucca elephantipes. To avoid the discussion regarding nursery nomenclature, we will submit that the nursery industry gets it wrong much of the time. That being said however, there was enough discrepancies in the written reference material on these plants that we decided to go with the flow and continue to call the shorter leaved heavier stemmed plant Yucca gloriosa while calling the larger leaved one Yucca elephantipes. After many years of urging by friends more knowledgeable than I on this subject, coupled with David Ferguson's comments in the Vol.73 of the Cactus & Succulent Journal and posts on the subject on the Agave usenet we decided in 2001 to change our listing for the plant we had long called Yucca gloriosa to Yucca elephantipes. We were reluctant to do this as we knew it would cause some confusion with our customers. To make it clear that we were still growing the same plant as before, we now list it as "Yucca elephantipes [Y. gloriosa, Hort.]". Hving made the decision to call this plant by this "new" name, we are still in a quandary what to call the yucca with the longer more luxiourious foliage that we had long referred to as "Yucca elephantipes"? It certainly does not resemble the description for the true Yucca gloriosa,which is a still narrow leafed species that comes from sandy lowlands of the southeastern US. The plant has 3-4 feet long by up to 4 inch wide leaves and like Y. elephantipes it is flexible and has a soft tip and small marginal teeth. The lower surface of the leaves are roughly the same color and texture as what we now call Yucca elephantipes but the leaf size and the glossy darker green upper surface are very different. These plants are both growing in Santa Barbara in very similar conditions so this is not a case of how a plant performs in one climate vs another as has been suggested in usenet discussions on Yucca elephantipes. These are two distinctly different plants.
Dylan Hannon, curator of the Huntington Botanic Garden Conservatory took this up with Dr. Lee Lenz at Rancho Santa Ana Botanic Garden who cited "Flora Mesoamericana" as giving Y. guatemalensis as the correct name for our the large swollen stemmed plant with shorter rougher textured leaves that we have called Y. gloriosa in California but then noted that the treatment of the genus by Dr. Joachim Thiede (Institute of Botany and Botanical Garden of the University of Hamburg) in The Illustrated Handbook of Succulent Plants (2001) listed Yucca elephantipes Regel as the valid name with Y. guatemalensis Baker and Y. gigantea Baker as synonyms and noting that Emily Jane Lott and Abisai Garcia-Mendoza in their 1994 treatment of Agavaceae the Flora of Mesoaericana and USDA 2001 The Plants database erroneously used the younger synonym Y. guatemalensis for this species. If we conclude that Yucca elephantipes is the current name for this species and it is synonomous with Y. guatemalensis and Y. gigantea,this still doesn't give us a clue as to what the name is for the more tropical,longer leaved plant picture below. The treatment in The Plant List (the collaboration between Missouri Botanic Garden and the Royal Botanic Garden Kew) has Yucca eliphantipes now as a synonym and Yucca gigantea as the valid name so perhaps they are all best called Yucca gigantea.