Lennooideae
Lennooideae, the sand food subfamily of the family Boraginaceae, composed of two genera and four species of parasitic plants. The unusual plants inhabit desert regions in Colombia, Venezuela, Mexico, and the southwestern United States, and many are considered rare. Though formerly treated as its own family (Lennoaceae), Lennooideae has been recategorized as a subfamily by the Angiosperm Phylogeny Group III (APG III) botanical classification system; its taxonomy remains contentious.
Members of the subfamily are obligate root parasites and totally lack chlorophyll. They send out structures called haustoria that penetrate the roots of other plants for food. Once the haustoria have entered the host roots, the parasite develops its aboveground portions, usually club-shaped, fleshy, yellowish or brownish stems with scalelike leaves. Attractive purple flowers are often formed in a ring along the top of the thick domelike stem.
The single species of Lennoa is quite variable. Flor de tierra (“flower of the earth”; L. madreporoides) usually grows on roots of the Mexican sunflower (Tithonia). The oval mushroomlike stem is 5–15 cm (2–6 inches) tall and is covered at maturity with small starlike flowers, violet with yellow throats.
Two species of Pholisma occur in southwestern North America: sand food (P. sonorae) and desert Christmas tree (P. arenarium). The succulent underground stems of sand food were used as food by Native Americans in what is now Arizona.