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Yucca brevifolia
Engelm.
Joshua Tree
Asparagaceae
Yucca brevifolia is a species of tree in the family Asparagaceae. Mostly native to the Mojave Desert, it is an iconic plant and the namesake of Joshua Tree National Park. It is sometimes grown as an ornamental.
Description
Yucca brevifolia is usually a solitary, often branching tree that grows up to 15 m tall. The leaves are sword-shaped, 15 to 35 cm long and 0.7 to 1.5 cm wide, stiff, green, smooth and hairless, with minute yellow teeth on the margins. Flowers are borne in tall, crowded panicles at the ends of branches, from late winter to mid-spring. Flowers are bell-shaped, 4 to 7 cm long, with 6 tepals (petals and sepals are not differentiated) that are greenish white to cream and lanceolate to oblong in outline. There are 6 stamens, with anthers 3 to 3.2 mm long on flattened filaments 1 to 1.2 cm long. The pistil is 2 to 3.5 cm long, with an ovoid ovary and a style that is 1.6 mm, and three distinct stigmas. These mature into the fruits, which are indehiscent (non-splitting) capsules that hang; fruits are ellipsoidal in shape and furrowed, 6 to 8.5 cm long, dry, and spongy. The seeds are 8 to 12 mm wide, black, and thin (FNAEC 1993).
The range of Yucca brevifolia overlaps with several other species of Yucca including the banana yucca (Yucca baccata), Mojave yucca (Yucca schidigera), soaptree yucca (Yucca elata), Utah yucca (Yucca utahensis), and narrowleaf yucca (Yucca angustissima). These species typically do not become tree-like, unlike Yucca brevifolia. Y. elata can sometimes form trunks, but its leaves are considerably longer (25 to 95 cm) and the fruit is dehiscent, splitting at maturity (FNAEC 1993).
The eastern half of the population differs subtly from the western half: western plants are taller (typically 6 to 9 m tall vs. 3 to 6 m tall), with a more distinct trunk. Western plants have more globose flowers and fruit rounded at tips while eastern plants have more elongated flowers and fruit tapering at tips. Because of these differences, the eastern population is sometimes recognized as a distinct species, the eastern Joshua tree (Yucca jaegeriana, as opposed to the western Joshua tree Yucca brevifolia sensu stricto) (Lenz 2007), but other authors recognize them as only varieties or completely synonymous with Y. brevifolia (FNAEC 1993).
The range of Yucca brevifolia overlaps with several other species of Yucca including the banana yucca (Yucca baccata), Mojave yucca (Yucca schidigera), soaptree yucca (Yucca elata), Utah yucca (Yucca utahensis), and narrowleaf yucca (Yucca angustissima). These species typically do not become tree-like, unlike Yucca brevifolia. Y. elata can sometimes form trunks, but its leaves are considerably longer (25 to 95 cm) and the fruit is dehiscent, splitting at maturity (FNAEC 1993).
The eastern half of the population differs subtly from the western half: western plants are taller (typically 6 to 9 m tall vs. 3 to 6 m tall), with a more distinct trunk. Western plants have more globose flowers and fruit rounded at tips while eastern plants have more elongated flowers and fruit tapering at tips. Because of these differences, the eastern population is sometimes recognized as a distinct species, the eastern Joshua tree (Yucca jaegeriana, as opposed to the western Joshua tree Yucca brevifolia sensu stricto) (Lenz 2007), but other authors recognize them as only varieties or completely synonymous with Y. brevifolia (FNAEC 1993).
Uses
Note: Please see the disclaimer regarding any information about medical or edible uses.
Yucca brevifolia can be grown as an ornamental in desert and rock gardens. It prefers full sun and coarse, well-draining soils; in its native range, it can tolerate desert conditions, so watering should be done only if in a prolonged drought. It is hardy in USDA zones 6 to 10 (MBG).
Native Americans and Europeans used the plant for various purposes. The trunk was used for building and making paper; the young terminal bud of the plant was harvested and eaten; the seeds were also eaten, or used as feed material (Esque et al. 2020a).
Native Americans and Europeans used the plant for various purposes. The trunk was used for building and making paper; the young terminal bud of the plant was harvested and eaten; the seeds were also eaten, or used as feed material (Esque et al. 2020a).
Distribution
Yucca brevifolia is mostly found in the Mojave Desert, but within the desert it can grow in a variety of habitats, from grasslands to juniper woodlands (Esque et al. 2020a). It is found at altitudes between 400 and 1800 m, in southeastern California, southern Nevada, western Arizona, and southwestern Utah (FNAEC 2003).
Status
Both of its interspecific taxa that constitute Yucca brevifolia are listed on the IUCN as “Least Concern”. Both Yucca brevifolia proper and jaegeriana are common enough within their range to meet this classification, but their populations are declining from fires, which have been increasing in intensity and frequency. Calculations of population dynamics suggest that Yucca brevifolia proper will suffer a decline of at least 7% while jaegeriana will suffer a larger decline of at least 13%. The threat of fire will become worse with climate change, and may force the taxa into a more threatened category (Esque et al. 2020a; Esque et al. 2020b).
References
Esque, T. C., DeFalco, L. A., Hodgson, W., Salywon, A., Puente, R. and Clary, K. 2020a. Yucca brevifolia. The IUCN Red List of Threatened Species https://dx.doi.org/10.2305/IUCN.UK.2020-3.RLTS.T117423077A117469962.en.
Esque, T. C., DeFalco, L. A., Hodgson, W., Salywon, A., Puente, R. and Clary, K. 2020b. Yucca jaegeriana. The IUCN Red List of Threatened Species https://dx.doi.org/10.2305/IUCN.UK.2020-3.RLTS.T162386466A162386497.en.
FNAEC (Flora of North America Editorial Committee), editor. 2003. Flora of North America, north of Mexico. Volume 26: Liliidae. New York: Oxford University Press.
Lenz, L. W. 2007. Reassessment of Yucca brevifolia and recognition of Y. jaegeriana as a distinct species. Aliso, 24: 97–104.
MBG (Missouri Botanical Garden), Yucca brevifolia. Plant Finder. [accessed 2022 Aug 10]. https://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?taxonid=282014
Esque, T. C., DeFalco, L. A., Hodgson, W., Salywon, A., Puente, R. and Clary, K. 2020b. Yucca jaegeriana. The IUCN Red List of Threatened Species https://dx.doi.org/10.2305/IUCN.UK.2020-3.RLTS.T162386466A162386497.en.
FNAEC (Flora of North America Editorial Committee), editor. 2003. Flora of North America, north of Mexico. Volume 26: Liliidae. New York: Oxford University Press.
Lenz, L. W. 2007. Reassessment of Yucca brevifolia and recognition of Y. jaegeriana as a distinct species. Aliso, 24: 97–104.
MBG (Missouri Botanical Garden), Yucca brevifolia. Plant Finder. [accessed 2022 Aug 10]. https://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?taxonid=282014
Description
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