All the many species of yucca (Yucca spp.) are drought-tolerant plants from arid areas. Their ability to survive drought and thrive in arid climates is dependent on their extensive and complex root system. The roots of various species are used for their soaplike sap and as food. Yuccas are also important to wildlife in their native habitats. Cassava root is also sometimes called yucca root, which leads to some confusion about the food value of yucca root.
Extensive, Fiberous Root System
Some yuccas have both a shallow, radial root system and a deep taproot. The shallow, radial root system spreads up to 35 feet around the yucca plant, intercepting and absorbing the brief, infrequent rainfall of the desert. This root system is effective at capturing the water before competing plants, producing a dry, bare patch of soil around the yucca.
All yuccas have fleshy taproots that extend deep into the soil, mining nutrients and water from deeper soils. These deeper roots can extend more than 20 feet into the ground and can be several inches in diameter. It is these roots that contain the saponin compounds that are used as soap and as the foaming agent for root beer. They were also used as a food source by Native Americans.
Many yuccas also produce rhizomes -- fleshy stems that grow along the surface of the soil. These rhizomes branch from the parent plant, then branch and re-branch, producing new plants along their length, forming an impenetrable thicket of yuccas. Not all yuccas of any given species produce rhizomes. Stem damage or certain environmental conditions seem to promote rhizome development. For example, Joshua tree (Yucca brevifolia) seems to produce many more rhizomes at the higher elevations of its range than in the lower deserts.
Yuccas need to be watered when they are first planted but once the root system is developed, they will not need supplemental water. Using weed whips or other equipment that damages the trunk can result in a thicket of yucca rather than a single plant. The root system that helps it survive and spread also makes it difficult to remove a yucca. New plants can sprout from any part of the root system, so major excavation is required to completely remove yucca plants.
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