The taxonomic (i.e., "scientific") identity of the invasive leafy spurge species found throughout the American West has recently undergone some reevaluation. In the past, this plant has typically been identified as Euphorbia esula, but in recent years a reassessment of the species and its potential Old World sources has suggested esula was a misidentification. Most of the publications listed below were published before this reassessment gained currency. Today a more generally accepted identification is Euphorbia virgata.