Euphorbia polygona is a spiny suсculent with simple or basally clumping, gray-green stems with beautiful "heads" of dark purple flowers. The stems are up to 5 feet (1.5 m) tall and up to 4 inches (10 st) in diameter. The fruits are globose with gray hairs and up to 0.2 inches (0.5 cm) in dianeter.