Common Name: Twisted-Leaf Yucca

General Information

Yucca rupicola is an evergreen shrub producing rosettes of spear-shaped leaves 35 - 60cm long and 17 - 40mm wide from a branching, underground stem. The plant usually forms an open colony of 2 - 15 rosettes[].
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 grown as an ornamental in gardens.
Yucca rupicola is a wide ranging, abundant species and even though there are threats and decline in parts of its
range, it occurs in several protected areas. The plant is classified as 'Least Concern' in the IUCN Red List of Threatened Species(2020)[].

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

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Range

Southern N. America - Texas, northeastern Mexico

Habitat

Limestone ledges and plains[]. Rocky hillsides of limestone ledges, open plains, woodlands; at elevations from 400 - 900 metres[].

Properties

Conservation Status	Least Concern
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Evergreen Shrub
Height	0.60 m
Pollinators	Hand
Cultivation Status	Ornamental, Wild

Cultivation Details

Yucca rupicola is a plant of semi-arid regions in southern N. America and, although capable of tolerating occasional short-lived temperatures down to around -5°c, does not grow very well in moist climates, being especially intolerant of winter wet[]. Plants have proven to be hardy outdoors in the drier areas of Britain[]., and flower regularly outdoors in Scotland[].
Thrives in any soil but prefers a sandy loam and full exposure to the south[]. It can succeed in light shade[]. Plants are hardier when grown on poor sandy soils[]. Established plants are very drought tolerant[].
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 crowns are monocarpic, dying after flowering[]. However, the crown will usually produce a number of sideshoots before it dies 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

Fruit - raw or cooked.

Flowers - raw or cooked. They are delicious raw, and can also be dried, crushed and used as a flavouring[].

Flowering stem - cooked and used like asparagus[].

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 and mats[82. 169].
The roots are rich in saponins and can be used as a soap substitute[].
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[].

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[].