Griffiths, Bulletin of the Torrey Botanical Club 43(2): 89, 1916
Opuntia semispinosa is a coastal species from southern CA and Mexico that has been variously lumped into O. occidentalis or confused with O. littoralis. We accept it as a stand-alone species. At one time there was much interest in the plant as a possible source of spineless Opuntia germplasm because some pads are spineless over part or all of the of the pad (hence “semi” spinosa), but this hope was not realized. Plants my reach 3- to 4-ft tall and be 6-ft wide. Plants may present as an untidy collection of branches and irregular cladodes. Segments may be oval or obovate and may be pointed at both ends (may seem almost rhomboid). Spines are white, but larger centrals may darken to brown at the base. Larger spines are often angular and twisted. O. semispinosa was initially collected at Santa Barbara, CA, San Pedro, CA, and near Tia Juana, Mexico. See the original citation.