Yucca is a genus of perennial shrubs and trees in the family Asparagaceae, subfamily Agavoideae.^[2] Its 40-50 species are notable for their rosettes of evergreen, tough, sword-shaped leaves and large terminal panicles of white or whitish flowers. They are native to the hot and dry (arid) parts of North America, Central America, South America, and the Caribbean. Early reports of the species were confused with the cassava (Manihot esculenta).^[3] Consequently, Linnaeus mistakenly derived the generic name from the Carib word for the latter, yuca.^[4] It is also colloquially known in the midwest United States as "Ghosts in the graveyard", as it is commonly found growing in rural graveyards and when in bloom the flowers appear as an apparition floating.

Distribution

Distribution of the capsular fruited species in southwest, midwest USA, Mexico's Baja California and Canada. Overview

The natural distribution range of the genus Yucca (49 species and 24 subspecies) covers a vast area of North and Central America. From Baja California in the west, northwards into the southwestern United States, through the drier central states as far north as Alberta in Canada (Yucca glauca ssp. albertana), and moving east along the Gulf of Mexico, and then north again, through the Atlantic coastal and inland neighbouring states. To the south, the genus is represented throughout Mexico and extends into Guatemala (Yucca guatemalensis). Yuccas have adapted to an equally vast range of climatic and ecological conditions. They are to be found in rocky deserts and badlands, in prairies and grassland, in mountainous regions, in light woodland, in coastal sands (Yucca filamentosa), and even in subtropical and semi-temperate zones, although these are generally arid to semi-arid.

Ecology

Yuccas have a very specialized, mutualistic pollination system, being pollinated by yucca moths (family Prodoxidae); the insect purposefully transfers the pollen from the stamens of one plant to the stigma of another, and at the same time lays an egg in the flower; the moth larva then feeds on some of the developing seeds, always leaving enough seed to perpetuate the species. Yucca species are the host plants for the caterpillars of the Yucca Giant-Skipper (Megathymus yuccae),^[5] Ursine Giant-Skipper (Megathymus ursus),^[6] and Strecker's Giant-Skipper (Megathymus streckeri).^[7]

Uses

Yuccas are widely grown as ornamental plants in gardens. Many species of yucca also bear edible parts, including fruits, seeds, flowers, flowering stems,^[8] and more rarely roots. References to yucca root as food often stem from confusion with the similarly spelled but botanically unrelated yuca, also called cassava (Manihot esculenta). Roots of soaptree yucca (Yucca elata) are high in saponins and are used as a shampoo in Native American rituals. Dried yucca leaves and trunk fibers have a low ignition temperature, making the plant desirable for use in starting fires via friction.^[9]

Cultivation

Yucca are widely planted in the western US as a landscape plant. Most species are generally heat and cold tolerant, requiring little care and low water. They offer a dramatic accent to a landscape design.

Joshua trees (Yucca brevifolia) are protected by law in some states and should not be wild collected without permit. As a landscape plant, they can be killed by excessive water during their summer dormant phase. For these two reasons they are avoided by landscape contractors.

Symbolism

The "yucca flower" is the state flower of New Mexico. No species name is given in the citation.

Species

		Yucca aloifolia	Aloe yucca, Spanish Bayonet
		Yucca angustissima	Narrowleaf yucca, Spanish Bayonet
		Yucca brevifolia	Joshua tree
		Yucca baccata	Banana yucca, datil
		Yucca constricta	Buckley's yucca
		Yucca decipiens	Palma China
		Yucca elata	Soaptree yucca
		Yucca filamentosa	Spoonleaf yucca, Filament yucca, or Adam's Needle
		Yucca filifera	Palma Chuna yucca
		Yucca flaccida	Flaccid leaf yucca
		Yucca glauca	Great Plains yucca
		Yucca gloriosa	Moundlily yucca, Adam's needle, Spanish Dagger
		Yucca grandiflora	Sahuiliqui yucca
		Yucca guatemalensis	Spineless yucca
		Yucca harrimaniae	Harriman's yucca
		Yucca intermedia	Intermediate Yucca
		Yucca jaliscensis	Izote
		Yucca kanabensis	Kanab yucca
		Yucca lacandonica	Tropical yucca
		Yucca madrensis	Soco yucca
		Yucca nana	Dwarf yucca
		Yucca pallida	Pale yucca
		Yucca periculosa	Izote
		Yucca recurvifolia	Curve-leaf yucca
		Yucca rigida	Blue yucca
		Yucca rostrata	Beaked yucca, Big Bend yucca
		Yucca rupicola	Texas yucca, or Twist-leaf yucca
		Yucca schidigera	Mojave yucca
		Yucca schottii	Hoary yucca or Mountain yucca
		Yucca standleyi
		Yucca thompsoniana	Thompson's Yucca
		Yucca thornberi
		Yucca torreyi	Torrey yucca
		Yucca treculiana	Texas bayonette, Trecul's yucca
		Yucca valida	Datilillo
		Yucca yucatana	Yucatan yucca

A number of other species previously classified in Yucca are now classified in the genera Dasylirion, Furcraea, Hesperaloe, Hesperoyucca and Nolina.

Taxonomic arrangement