Yucca ( ) is both the scientific name and common name for a genus native to North America from Panama to southern Canada. It contains 50 accepted species. In addition to yucca, they are also known as Adam's needle or Spanish-bayonet. The genus is generally classified in the asparagus family in a subfamily with the Agave, though historically it was part of the lily family. The species range from small shrubby plants to tree-like giants, such as the Joshua tree. All yuccas have rosettes of leaves that taper to points and inflorescences with many flowers that are mainly cream white with thick petals. Though adapted to a wide range of climates the plants are xerophytes, ones that specialize in dry living conditions.
The tight relationship between the yucca plants and their pollinators, the yucca moths from the genera Tegeticula and Parategeticula, is a well known example of evolutionary mutualism. They are an important part of the ecology of North American deserts, providing shelter to small animals and creating habitats. The human uses of yuccas include garden plants, as food, and for extracts. The flower petals of various species are eaten as a part of local cuisine, particularly in Central America and Mexico. Historically, the yucca was extensively used for its fibers to make cords, baskets, mats, and sandals. It continues to be used by native peoples for traditional soaps.
Description Yuccas are perennial plants with long, pointed sword shaped leaves in one or more rosettes, circular arrangements of leaves. Usually the leaves are stiff and fibrous, but a few species have fleshy leaves. The leaves are numerous and arranged in spirals at the ends of stems or branches. Plants can be small shrubs or large resembling trees. The surface of the leaves are hairless, but some have a very rough surface. About half of all species have fibers that peel off the edges of the leaves. Their color can be bright green, gray-green, or pale blue. The leaves never have spines on their edges, but may be very finely toothed. Some yucca species reproduce by underground rhizomes and form colonies of plants, but this feature is rare in the fleshy-fruited yuccas, which will usually produce new sprouts at the base of the plant from nodule-like growths.
Plants without stems or trunks grow from a thick underground caudex, a modified stem with growth at the end like in a palm tree. Species that do not have trunks tend to be found in colder areas such as the Rocky Mountains, Great Plains, and eastern United States. Species with trunks are more common in the subtropics, deserts, and tropics to the south. The largest of these tree yuccas is Yucca brevifolia, commonly known as the Joshua tree in the American southwest. The Joshua tree can reach up to in height. Every species grows in soil, however Yucca lacandonica usually grows as an epiphyte.
Some species have a scape, a long flowering stem without any leaves or bracts along its length. These are always less than in diameter. The inflorescence is usually upright, but in a few species bends over and hangs downward. The inflorescence can be a panicle, where the flowers are on branches off the main stem, or a raceme, where the flowers are attached directly by flower stalks to the main stem. Though the plants live for many years and flower multiple times, each inflorescence dies after setting seed.
The flowers are large and showy, ranging from bell shaped to round like a globe. The six tepals are white to cream or slightly green in color. They are thick and leathery in texture, and in many species the three outermost tepals will have red, pink, maroon, purple, or brown streaks.
In about half of the species the fruit is a dry capsule. In the other half, it is a fleshy fruit. Inside the fruit, the seeds are tightly packed, flat, and black in color. Dry capsules are held in an upright position while soft capsules hang downwards.
Due to similar characteristics of many species it is difficult to identify them without flowers or fruits. Many characteristics taken together are needed to make identifications, often including the size and color of the pistil, style, and flowers while alive. Yuccas are distinct from Agave due to typically having less succulent leaves, thicker flower petals, and a lack of spines on leaf edges.
Taxonomy Yucca was first described and named by Carl Linnaeus in his book Species Plantarum, published in 1753. The first work on the genus as a whole was published by George Engelmann in 1873. A lectotype for the genus, a specimen of Yucca aloifolia, was designated by Nathaniel Lord Britton and John Adolph Shafer in 1908.
In 1902 William Trelease published a paper separating out Clistoyucca and Samuela from Yucca, along with his 1893 separation of Hesperoyucca from the genus. Susan Delano McKelvey argued against this separation, though she recognized them as sections of Yucca. McKelvey did allow that Hesperoyucca might be recognized as a genus writing, "since a number of flower and fruit characters differ from those in all other sections". DNA investigations in the 1990s found support for Hesperoyucca. As of 2025, Hesperoyucca is listed as accepted.
Prior to the 1950s Yucca was placed in Liliaceae, the lily family, due to having a superior ovary. Since that time, evidence of it being more closely related to the Agave genus has been accepted. In particular, the discovery that Yucca, like plants in Agave, has 5 large and 20 small chromosomes was a large factor in reconsidering their relationship. The APG III system, published in 2009, placed the genus into the family Asparagaceae in the Agavoideae subfamily. This classification continued in APG IV. However, some botanists prefer to classify this subfamily as a family named Agavaceae.
Species
Plants of the World Online (POWO) and World Flora Online (WFO) both list 50 valid species. In addition, POWO lists three other species, Yucca jaegeriana , Yucca muscipula , and Yucca pinicola , that WFO lists as unchecked or as a synonym of another species. There are also two natural hybrids, Yucca × schottii, which was formerly listed as a species under various names, and Yucca × quinnarjenii.
Names In 1737 Linnaeus, in setting out his rules for the names of genera, wrote, "Generic names which have not a root derived from Greek or Latin are to be rejected". However, in the case of Yucca and several other names, he violated his own rule by adopting names derived from other languages. The word was borrowed from the Carib language by Spanish as juca, starting with Amerigo Vespucci in 1497 referring to cassava. It was first used to refer to the unrelated plants of the genus Yucca in a German travel account published in 1557. This was used as the genus name by Linnaeus in Species Plantarum.
The name yucca is used as an English common name for plant species in the genus. It is pronounced (YUCK-uh) in both British English and American English, but may also be pronounced (YOO-kuh) in British English. It is also known as Adam's needle or as Spanish-bayonet. Other common names for some species include Spanish dagger, shin dagger, soapweed, or soaptree. In the plant trade they are sometimes known as palm lilies. The name yucca can be confused with cassava, though the spelling yuca is often used to distinguish the food from plants in Yucca.
The Aztecs living in Mexico call the local yucca species in Nahuatl, which gave the Spanish .
Range and habitat
The natural range of the yuccas stretches across much of southern North America from Panama in the south as far north as Alberta in Canada. The exact extent is disputed as though Yucca gigantea is listed by Plants of the World Online (POWO) and World Flora Online (WFO) as native to Central America, other sources like World Plants list it as introduced to all the nations of Central America. Likewise, Yucca flaccida is listed as native to Ontario by POWO, WFO, and World Plants, but is listed by the Database of Vascular Plants of Canada as introduced.
Yuccas are generally accepted to be introduced to the islands Caribbean. Various species have also escaped from cultivation in Europe as far east as Poland and Romania. They grow as an introduced species in Turkey, Pakistan, and Bangladesh in Asia. In Africa they are reported in Tunisia and KwaZulu-Natal and Free State in South Africa. They have been introduced to South America in Ecuador, Bolivia, Uruguay, and Argentina. In Australia Aloe yucca (Yucca aloifolia) has naturalized in Western Australia, Queensland, New South Wales, and the Australian Capital Territory. It is doubtfully naturalized on Lord Howe Island and naturalized on Norfolk Island. Two other species, Yucca gloriosa and Yucca whipplei, may also be naturalized in Australia. Spineless yucca (Yucca gigantea) is considered the most common variety in Australia. They are listed as an environmental weed in New Zealand having been found 31 times outside of cultivation.
The yuccas are xerophytic, plants with adaptations to dry environments, with even those native to rainy habitats growing better when in drier areas. The smaller, freeze-tolerant species of yucca have two centers of diversity, one in Texas and the other on the Colorado Plateau. They are found generally to the north and east of the range in Chihuahuan Desert, the Trans-Pecos region, the Rocky Mountains, the Colorado Plateau, and the Great Plains. Tree-like yuccas with fleshy fruits have a center of diversity in the Sonoran Desert. They are found mainly in Mexico, while the tree like yuccas with spongy fruits are found only in the Mojave Desert.
Ecology
Yuccas have a very specialized mutualistic system of pollination. Yucca moths in genus Tegeticula or Parategeticula pollinate the flowers and then lay their eggs in the seed capsules of yuccas. Some species of Tegeticula provide no benefit to the yuccas, laying eggs but not pollinating the flowers due to lacking the specialized parts for carrying pollen. Almost all species are pollinated by one or more species of these moths with one species, Aloe yucca (Yucca aloifolia), documented to revert away from mutualism to a generalist pollinator when the moths are absent. This mutualism was first documented by Charles Valentine Riley in 1873, and its discovery elicited much excitement in the scientific community. In a 1874 letter to his friend Joseph Dalton Hooker, Darwin called it "the most wonderful case of fertilisation ever published".
Instances of animal behavior that are exclusively aimed at pollination of plants, rather than just accompanying the animal gathering food, are quite rare. Female yucca moths have tentacle-like mouth parts that they use to gather pollen and then to deposit it on the reproductive parts. In the 150 years following the discovery of this relationship it became one of the most famous of the documented plant and animal mutualisms along with the fig wasps and fig trees. The association between the yuccas and the yucca moths is quite ancient, with a molecular clock estimate that it began between 51.3 and 31.7 million years ago with them becoming pollinators 35.6 million years ago ±9 million years.