The Biogeography of  Spanish Dagger (Yucca gloriosa).
 

by Ricky O'Neal, student in Geography 316  Fall 2005

Thank you for visiting our site. This web pages was written by a student in Geography 316: Biogeography and edited by the instructor, Barbara Holzman, PhD.  All photos and maps are posted with specific copyright permission for the express use of education on these web pages. The students have tried to be as accurate as possible with the information provided and sources and references are cited at the end of each page.

Species Name: Yucca gloriosa 

 

Kingdom:  Plantae Division: Magnoliophyta Class:  Liliopsida Order:  Liliales Family:  Agavaceae Genus: Yucca Species: Yucca gloriosa  Common Name:  Spanish Dagger
	Figure 1:  Long trunked Spanish dagger (Photo by R. O'Neal)

 Description of Species:

The Spanish dagger is a common plant that is used in many gardens and has a distinct look to it.  Many people grow the Spanish dagger in there gardens because of the exotic look to it and the size that it may get.  Even though the plant type is considered a shrub, the Spanish dagger can grow anywhere from 6 feet to 16 feet high.  In some areas it may even grow taller.  The leaves are a simple linear shape with a length of 18 to 36 inches and stay green in color year around (Gilman 1999) (Figure 2).  The leaves are also thicker near the base and in the middle, ranging from a width of 3 to 5 inches, and come to a gradual point at the tip of the leaf (Figure 2).  Multiple leaves grow out of the Spanish daggers trunk or stem, fanning out in all directions near the top, looking some what like a palm tree (Figure 1).  The leaves may also grow further down the trunk and in some cases the whole trunk may be covered in leaves.  The Spanish dagger can be multi-trunked or have clumped stems (Gilman 1999) (Figure 3).  However, it can be developed to grow closer to the ground with a short, single trunk (Gilman 1999).  The trunks are light gray to brown in color, looking similar to a tree trunk, and the stems are green in color and are very thick in size (Gilman 1999). The white flower typically grows directly over the leaf blades and has a pleasant fragrance, usually blooming in summer and spring (Gilman 1999).  The Spanish dagger occasionally grows an oval shaped brown fruit that is about 1 to 3 inches in length and may be consumed by humans (Gilman 1999). 

 

Figure 2: Leaf structure of Spanish dagger (Photo by R. O'Neal)	Figure 3: Multi-trunked Spanish dagger (Photo by R. O'Neal)

Natural History:

Over time the Spanish dagger (Y. gloriosa) has, and still is, one of the most misrepresented plants in North America (Gilman 1999).  Many often confuse it with the Spanish bayonet (Yucca aloifolia) because of its similar appearance in both leaves and flowers (Gilman 1999).  However, the Spanish dagger's leaf margins are smooth, whereas the leaf margins on the Spanish Bayonet are more rough (Gilman 1999).  Moreover, the outer or older leaves on the Spanish dagger bend towards the ground with age and the Spanish bayonet leaves stay the same over time (Gilman 1999).  Finally, one of the main differences between the two occurs underground.  The Spanish bayonet tends to topple over and re-root itself, where the Spanish Dagger is stationary (Floridata 2005).  Eventually, the Spanish dagger would be cultivated out of the southeast region of the United States and spread across the world.   

Evolution:
The evolution of the Yucca plant is derived from the Agavaceae family.  The Agavaceae family consists of over 300 species and the Yucca genus has nearly 50 species  (Hodgkiss 2005).  Because all Yucca’s are totally dependent upon the Yucca moth for pollination, they share the same biological fate together (Ramsay and Schrock 2003).  This mutualistic relationship has helped the Yucca evolve over time and form various species. 

Since 1896, Y. gloriosa has been cultivated all across the United States, deriving from the south eastern states (Key 2003).  In 1596, the Spanish dagger was the first Yucca to be introduced into the UK, coming from the coastal sand dunes of the South Eastern United States (Hodgkiss 2005).   Branches and trunks from the Spanish dagger can be cut off and rooted to propagate the plant (Hodgkiss 2005).  This is likely the way it spread globally and adapted to several environments.  Because of the global spread of the Spanish dagger and the many climates that it can grow in, their leaves vary in length, thickness, and color, and its flowers vary from simple to complex (Key 2003).    

Distribution::  

Figure 4:  Spanish dagger distribution in California (Map by R. O'neal)	Figure 5:  Spanish dagger distribution in the United States (Map by R. O'Neal)

Although Y. gloriosa is a native plant to the southeastern region of the United States, it is cultivated and can grow as far as the western region of the states of Washington, western Oregon, most of California, southern Nevada, Arizona, and southern New Mexico (Figure 5).  It is also prevalent in Texas, southern Oklahoma, Louisiana, Arkansas, Mississippi, Alabama, Georgia, and Florida (Figure 5).  On the East Coast, it grows through South Carolina, North Carolina, east Virginia, Maryland, Delaware, and south New Jersey (Figure 5).   It is native to the southeast because it grows best on coastal dunes and shell mounds, which are common in the Atlantic from North Carolina to northeastern Florida.  It is also a high salt tolerant plant, thriving in coastal areas, including the San Francisco Bay Area of California.  However, in the right conditions it is or may be cultivated in any area with a lot of sun and in sandy well-drained soil.  Y. gloriosa does best with full sun, but with partial shade the plant can still grow very well.  In colder regions, Y. gloriosa will grow with a frost tolerance of  22°F (-6°C) and may grow up to 5000ft elevation (Faucon 2005). One aspect of Y. gloriosa is that it is a very drought tolerant plant, making it an excellent cultivated plant in low water landscapes.  Moreover, it is commonly used as an attractive backdrop in a succulent or rock garden.  In California, Y. gloriosa can be found in almost any landscape or region, except for areas on the eastern side of the Sierra Nevada Mountains and in the far north region (Figure 4).   Finally, in order for the Y. gloriosa to be pollinated in the wild, the yucca moth must be present in the region of growth, otherwise the plant must be manually pollinated viable seeds are needed.  This is commonly done in cultivated areas such as California.                

Other interesting issues:
 

The Spanish dagger is commonly used as a garden plant all across California.  Many landscapers and gardeners plant Spanish daggers as a backdrop, or alone, because of its unique look and its durability.  The plant can also be seen at several parks all over the country, including Alcatraz Island National Park in San Francisco California (Figure 6).  On Alcatraz Island, the Garden Conservancy maintains the Spanish daggers and all of the other plants as part of the Alcatraz Garden Restoration Project.  At least once a week, volunteers from the Garden Conservancy go to the Island to help maintain and restore the historic gardens and plants of Alcatraz Island, including the multiple Spanish daggers that are growing there today.  If you are interested in planting a Spanish dagger in your garden, most nurseries carry them or have access to them in states where they may be cultivated.

Figure 6: Cultivated Spanish daggers on Alcatraz Island National Park

Bibliography

Botanica.  1999.  Welcome Rain Publisher, NY.  p 940.  

Gilman, E.F.  1999.  Yucca gloriosa.  University of Florida; Institute of Food and Agricultural Sciences.  [On-line] http://hort.ifas.ufl.edu/shrubs/YUCGLOA.PDF  [March 11, 2005].

Faucon, P. 2005. Spanish Dagger.  Desert Tropicals. [On-line] http://www.desert tropicals.com/Plants/Agavaceae/Yucca_gloriosa.html [April 20,2005].

Floridata Marketplace.  2005.  Yucca gloriosa.  Floridadata.com L.C.  [On-line] http://www.floridata.com/ref/Y/yucc_glo.cfm [March 11, 2005].

Key, T.  2002.  Hardy Yuccas. The National Council for the Conservation of Plants and Gardens.  [On-line] http://www.nccpg.com/Default.Aspx?Page.Aspx?page=180 [April 20, 2005].

Hodgkiss, R.J.  2005.  The Yucca Page.  The Succulent Plant Page.  [On-line] http://www.succulent-plant.com/yucca.html [April 20, 2005].

Ramsay, M and J.R. Schrock. 2003.  The Yucca Plant and the Yucca Moth.  The Kansas School of Naturalist.  [On-line] http://www.emporia.edu/ksn/v41n2-june1995/ KSNVOL41-2.htm [April 20, 2005]

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