How often have you seen a picture of a yucca or an agave in a newspaper with a caption commenting on this "cactus"? Too often, from the viewpoint of naturalists! Although cacti, yuccas, and agaves fall into the descriptive category of "succulents", cacti are not at all closely related to the others, being in a family all of their own. In other words, just having a fleshy body and sharp points to fend off enemies does not make a cactus.
Botanists usually consider flower types important in classifying
plants—and if you've gotten up close and personal with flowers, you know that the
bloom of a cactus has numerous overlapping petals extending from an open center and
isn't anything like the bell-shaped yucca blossom. There are a lot of other
important features as well. Agaves and yuccas are practically all leaves, while most
cacti are all stems. The pain of a close encounter is about the only thing in common,
for the moisture-laden tissues must fend off attacks from a myriad of hungry and
thirsty animals.
Listen to the Audio (mp3 format) as recorded by KTEP, Public Radio for the Southwest.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.
Cactus and yucca blossoms; images may be clicked on for larger pictures.
Vines, R. A. 1960. Trees, shrubs, and woody vines of the Southwest. University of Texas Press, Austin, 1104 pp.
DesertUSA. Information and images of a number of cacti and other succulents.