Eriogonum evanidum is a rare species of wild buckwheat known by the common name vanishing wild buckwheat. It is native to southern California and Baja California, where it has been collected from widely scattered areas. Most historical occurrences are now extirpated and the plant has not been collected since 1967. Some sources suggest that it is probably extinct. The plant was described as a new species in 2004 using specimens that were set aside from a collection of Eriogonum foliosum on the basis of some morphological characteristics. The specimens came from several locations in the southern California mountains, including Bear Valley in the San Bernardino Mountains and Pine Valley east of San Diego. This is an annual herb producing thin, erect stems about 10 or 20 centimeters tall surrounded at the base by small, woolly leaves up to a centimeter long by a centimeter wide. The flowering stem branches from the main stem and is a few centimeters long. It is studded with tiny clumps of yellowish flowers each around a millimeter long.