YELLOW [Illustration: Cercidium floridum Cercidium microphyllum] Common Names: PALOVERDE, YELLOW PALOVERDE, BLUE PALOVERDE Arizona deserts: (_Cercidium microphyllum_). Pale yellow. April-May. Arizona desert. (_Cercidium floridum_). Bright yellow. April-May. Pea family. Size: Green-barked tree up to 25 feet high. Arizona Paloverdes (meaning green stick) are large shrubs or small trees abundant along washes in the hotter, drier portions of the Sonoran Desert. When in blossom in the springtime, they appear as masses of pale yellow or golden bloom, and are a glorious sight, both as individual trees and massed as borders along the courses of washes which they mark with a line of color winding across the desert floor. During the dry season, they are without leaves, but are readily recognized by the bark, yellowish green in the case of _C. microphyllum_; blue green in _C. floridum_. After the petals form, seeds form in bean-like pods which are not relished by livestock, but are eaten during periods of drought and when other forage is scarce. Indians ground the seeds into meal. When the trees are in blossom, they attract myriads of insects, some of which, including Honeybees, seek the nectar. Wood is soft and the branches are brittle and easily broken. It is unsuited for fuel as it burns rapidly, leaves no coals, and gives off an unpleasant odor. YELLOW [Illustration: Polanisia trachysperma] Common name: CLAMMYWEED Arizona desert: (_Polanisia trachysperma_). Pale yellow. June-September. Texas desert: (_Polanisia uniglandulosa_). Pale yellow. June-September. Caper family. Size: 1 to 3 feet tall. Clammyweed is not limited in its range to desert areas, but is found as far north as Saskatchewan and British Columbia. However, it is also a common annual in Texas, New Mexico, and Arizona at elevations between 1,200 and 6,000 feet, and is usually found in abundance in the sandy channels of dry stream beds. It somewhat resembles both Yellow Beeweed (_Cleome lutea_) and Jackass-clover (_Wislizenia refracta_.) YELLOW [Illustration: Tribulus terrestris] Common names: PUNCTUREVINE, BURNUT, BULLHEAD, (_TORRITO_) Arizona, California, and Texas deserts: (_Tribulus terrestris_). Pale yellow. Summer. Caltrop family. Size: Prostrate, stems 2 to 6 feet long. A troublesome annual vine-like weed naturalized from southern Europe, the Puncturevine has established itself throughout the Southwest below 7,000 feet. Although fairly readily controlled by cultivation, the plant spreads rapidly in sandy, dry wastelands, often taking over vacant lots in towns, and areas in the desert where it finds sufficient moisture.