Mark A. Miller
Family
Agavaceae
Botanical Name
Yucca brevifolia
Plant Common Name
Joshua Tree
General Description
This is likely one of the best known yuccas due to the popularity of Joshua Tree National Park in Twentynine Palms, California. Yucca brevifolia is a succulent, evergreen that reaches great heights with a candelabra of branches topped with rosettes of spiky leaves. A Mojave Desert endemic, it exists in sagebrush, pinyon-juniper and desert grassland ecosystems where it survives the harshest growing conditions. This is a very slow-growing, very long-lived yucca. Mature specimens reach huge, tree-like heights and develop open, rounded crowns and thick, corky trunks.
Tall, branched candles of ivory or white flowers appear at various times in late winter to late spring. Though open during the day, Joshua tree blooms are only pollinated in the night by certain moths; specific Yucca species often have single moth species that pollinates them, a true instance of coevolution. At night, the flowers emit a unique, soapy fragrance and turn upwards to receive their pollinators. The moths gather balls of sticky pollen and actively pollinate the flowers. In turn, the female moths lay their eggs in the flower’s ovaries and plug the ovipositor hole with a ball of sticky pollen. When the larvae hatch, they consume some, but not all, of the developing seeds. Enough seeds remain to fall to the ground and germinate. This is one of the most interesting and well-researched plant/pollinator relationships. The capsule fruits are large, oval, fleshy and mature from green to papery brown.
Joshua tree is easy to grow but is not well-suited to the intensely cultivated gardens of residential areas where irrigation and fertilizers are used. Grow it in full sun and well-drained soil with average to low fertility. It thrives in poor, rocky or sandy desert soils. The summers must be long, hot and dry. Summer humidity and rains quickly leads to plant decline and death.
In the landscape, Joshua tree is typically grown as a specimen plant to draw visual focus to a natural desert garden design. It offers fine-textured foliage along with bold, architectural form. Plant it near a rustic path where the night blooms are best enjoyed on a stroll.
Characteristics
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AHS Heat Zone
12 - 7
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USDA Hardiness Zone
6 - 10
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Sunset Zone
9, 10, 11, 12, 13, 14, 15, 16, 18, 19, 20, 21, 22, 23
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Plant Type
Cactus or Succulent
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Sun Exposure
Full Sun
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Height
20'-40' / 6.1m - 12.2m
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Width
10'-20' / 3.0m - 6.1m
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Bloom Time
Early Spring, Spring, Late Winter
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Native To
Southwestern United States, Mexico
Growing Conditions
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Soil pH
Acidic, Neutral, Alkaline
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Soil Drainage
Well Drained
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Soil type
Loam, Sand
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Tolerances
Drought
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Growth Rate
Very Slow
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Water Requirements
Xeric/Desert
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Habit
Upright/Erect
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Seasonal Interest
Spring, Summer, Fall, Winter
