Yucca species: Yucca

Family

Agavaceae

Common Names

Yucca, Spanish bayonet, Spanish dagger

Plant Description

A genus of some 40 species indigenous to the drier regions of North America, yuccas are well adapted to dry conditions, and therefore are popular xeriscape plants. They form rosettes of stiff, sword-like leaves often tipped with a sharp spine. Some species develop a woody, branching, trunk as they mature. Inflorescences consist of tall, showy panicles of pendent, creamy-white, bell-like flowers (Fig. 405). Some of the larger species of yucca may take many years before they bloom. Many species of yucca require a specific insect, the yucca moth, to pollinate the flowers. The fruits are fleshy capsules that turn brown when ripe, splitting open to release numerous seeds. Other members of the Agavaceae that are similar include agave (Agave spp.) and sacahuiste, bunch grass, or bear grass (Nolina spp.).

Figure 405. Yucca species.

Toxic Principle and Mechanism of Action

Members of the Agavaceae contain steroidal saponins that cause a crystalloid cholangiohepatopathy. As a result of the precipitation of the calcium saponins in the bile ducts, the liver is unable to excrete phylloerythrin normally, and hepatogenous photosensitivity results. Poisoning is most likely in ruminants that might graze the plants when there is little else available.

Risk Assessment

Yuccas have minimal risk of being poisonous to household pets. Some species, however have terminal spines that can cause mechanical injury.

Clinical Signs

Vomiting and diarrhea could be anticipated in a dog or cat that chewed upon or swallowed yucca leaves. The problem is usually self limiting. Weight loss, and photosensitivity suggestive of liver disease can be expected in ruminants that graze yucca in dry range conditions. Animals with photosensitization should be kept in the shade and removed from the source of the yucca.