The two species readily hybridize, and a few spiny wild types often develop among globe artichoke seedlings. See Comparison of spiny-leaved thistles . Artichoke thistle was introduced from the Mediterranean region as a vegetable and ornamental. At publication time, the fly's impact on artichoke thistle populations is unknown. Larvae feed only on mature flower heads, thus commercial artichokes are not significantly affected.
Seedlings develop a deep taproot during the first year.
Rosette leaves often die during the first summer and re-grow when rains commence in fall. Upper surfaces loosely and lower surfaces densely covered with white to gray woolly hairs. Cultivated types may lack or have weak spines. Tapoot thick, fleshy, can penetrate soil to depths up to 2 m. Roots fragments often generate new shoots. Phyllaries ovate, overlapping in several series, tapered to a stout point .