This member of the carrot family has tough, blue-green, yucca-like, parallel-veined, spiny leaves, with smooth, rigid stems. It bears thistle-like flower heads at the branch ends, made up of small greenish-white (turns bluish with maturity) globes mingled with pointed bracts. Prospers in well-drained soil types. Mature plants can be divided in late spring or early fall. It can be an aggressive self-seeder, so remove seed heads to keep the plant in check. Drought tolerant. Has deep tap roots so transplants poorly.