Common Name: Joshua Tree

General Information

Yucca brevifolia is an evergreen tree that can grow up to 15 metres tall. It usually produces a single trunk, occasionally several; the trunk can be unbranched, especially when young, often becoming multibranched as it grows older. A rosette of spear-shaped leaves 15 - 35cm long and 7 - 15mm wide is produced at the end of each trunk and banch[, ].
The plant is harvested from the wild for local use as a food and source of materials. The roots of Yucca species are rich in saponins and have a wide range of applications. The plant is often grown as an ornamental in gardens.

Known Hazards

The roots contain saponins[].
Although poisonous, saponins also have a range of medicinal applications and many saponin-rich plants are used in herbalism (particularly as emetics, expectorants and febrifuges) or as sources of raw materials for the pharmaceutical industry. Saponins are also found in a number of common foods, such as many beans.
Saponins have a quite bitter flavour and are in general poorly absorbed by the human body, so most pass through without harm. They can be removed by carefully leaching in running water. Thorough cooking, and perhaps changing the cooking water once, will also normally remove most of them. However, it is not advisable to eat large quantities of raw foods that contain saponins.
Saponins are much more toxic to many cold-blooded creatures, such as fish, and hunting tribes have traditionally put large quantities of them in streams, lakes etc in order to stupefy or kill the fish and make them easy to catch[].

Botanical References

Range

South-western N. America - California, Nevada, Utah, Arizona, northern Mexico

Habitat

Arid mesas and mountain slopes; usually at elevations from 650 - 2,200 metres[].

Properties

Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Evergreen Tree
Height	9.00 m
Growth Rate	Slow
Pollinators	Moths
Cultivation Status	Ornamental, Wild

Cultivation Details

Yucca brevifolia is native to semi-arid regions with hot summers and cold winters. In such a climate it is known to survive winter temperatures falling as low as -25°c whilst summer temperatures can go as high as 51°c[]. It grows in areas where annual rainfall can be as low as 100mm or as high as 430mm with a summer drought of around 3 months[]. The plant will be less hardy than this in moister climates.
Thrives in any soil but prefers a sandy loam and full exposure to the south[]. Plants are hardier when they are grown on poor sandy soils[]. Prefers a hot dry position[], disliking heavy rain[]. Established plants are very drought resistant[]. Plants are tolerant of alkaline and saline soils[].
A slow-growing plant[].
Plants will often survive fire - if the fire is not too hot then the crown of older plants that have shed dead leaves can survive; in hotter fires the plant will often resprout from the roots[].
The flowers of this species are malodorous[].
Yuccas are pollinated by small, white Yucca moths (Tegeticula yucasella and related species) with which they have a special plant-insect mutualism. At night, the fragrant flowers attract the female moth that feeds on the nectar. She then rolls pollen from the flowers into a ball that is three times the size of her head and carries the pollen ball to the next flower. There, she first lays eggs inside the immature ovary and then deposits the pollen on the flower’s stigma ensuring that seeds will form to feed her progeny. Because the larvae mature before they are able to consume all of
the seeds (60 to 80% of the seeds remain viable), the plants are able to reproduce as well[]. In regions where the moth cannot live and, if fruit and seed are required, then hand pollination is necessary[]. This can be quite easily and successfully done using something like a small paint brush.
Individual terminal shoots are monocarpic, dying after flowering[]. However, the stem will then usually produce a number of sideshoots, and these will grow on to flower in later years[, ].
Plants in this genus are notably resistant to honey fungus[].
Members of this genus seem to be immune to the predations of rabbits[]

Edible Uses

Flowers - cooked[, ]. The flower buds, before opening, can be parboiled in salt water to remove the bitterness, drained and then cooked again and served like cauliflower[]. The opened flowers are rich in sugar and can be roasted and eaten as candy[].

Fruit - cooked[]. The fruits can be roasted then formed into cakes and dried for later use[]. The ellipsoid fruits are dry and spongy, they can be 60 - 85mm long[].

Root - raw, boiled or roasted[].

Seed[]. Gathered and eaten by the local Indians[]. No further details are given, but it is probably ground into a powder and mixed with cornmeal or other flours and used for making bread, cakes etc.
Immature seedpod[]. No more details given.

Medicinal

The roots are antiinflammatory, antitumor, antiviral[].
The roots of Yucca species are rich in saponins and medicinally active compounds. The roots, harvested when the plant is not in flower, are used to make a health-promoting drink. It has been shown to lower cholesterol and triglyceride levels in the blood, to lower blood pressure and to reduce symptoms of osteoarthritis such as pain, swelling and stiffness. Yucca schidigera seems to be the species most often quoted, though all species contain the saponins[, ].
Taken orally, the root is used in the treatment of osteoarthritis, hypertension, migraine headaches, colitis, stomach disorders, hypercholesterolemia, diabetes, poor circulation, and liver and gallbladder disorders[].
Applied topically, it is used to treat sores, skin diseases, inflammation, bleeding, sprains, broken limbs, joint pain, baldness, and dandruff[].

Many compounds from yucca have been used in the synthesis of new drugs[].

Other Uses

A fibre obtained from the leaves is used for making ropes, baskets, sandals, clothing and mats[, , ].

The whole leaf can be woven into mats etc and it can also be used as a paint brush[, ].

The dark red core of the roots has been used as a pattern material in coiled baskets[]. The core is split into strands, soaked and worked in with the coiling so that the colour is always on the outside[].

Red and black dyes have been obtained from the roots[].

The roots are rich in saponins and can be used as a soap substitute[, ]. It makes a good hair wash[, ].
The juice of the plant has a wide variety of uses. In agriculture it is used as a base in liquid fertilizers where its ability to reduce surface tension of irrigation water greatly assists penetration in heavy soils; it assists in soil flocculation to a marked degree; it serves as a carrying agent for the plant-food chemicals[]. The yucca extract itself is rich in the vital minor elements including boron, iron, magnesium, manganese, copper and zinc[].
The juice is said to be widely used as a carbon dioxide stabilizer in the control of oil fires, and saponin from yucca is considered a good base for soaps, shampoos, cleansing powders, and tooth pastes and powders[].

Wood - light, soft, spongy, difficult to work[]. The trunks were used in ancient cliff dwellings in Arizona[]. The trunks are sometimes cut into thin layers and used as wrapping material, or manufactured into boxes and other small articles[].

Propagation

Seed - sow spring in a greenhouse. Pre-soaking the seed for 24 hours in warm water may reduce the germination time. It usually germinates within 1 - 12 months if kept at a temperature of 20°c. Prick out the seedlings into individual pots when they are large enough to handle and grow them on in the greenhouse or cold frame for at least their first two winters. Plant them out into their permanent positions in early summer and consider giving them some winter protection for at least their first winter outdoors - a simple pane of glass is usually sufficient[].. Seed is not produced in Britain unless the flowers are hand pollinated.
Root cuttings in late winter or early spring. Lift in mid spring and remove small buds from base of stem and rhizomes. Dip in dry wood ashes to stop any bleeding and plant in a sandy soil in pots in a greenhouse until established[].
Division of suckers in late spring[]. Larger divisions can be planted out direct into their permanent positions. We have found that it is best to pot up smaller divisions and grow them on in light shade in a greenhouse or cold frame until they are growing away well. Plant them out in the following spring.