is one of the more untidy-looking plants of this genus, forming dense, low, clusters of upwards-pointing, unsymmetrical, green or yellowish green leaves, completely lacking teeth but sometimes edged by thin white filaments. Leaves grow to between 10 and 15 inches in length, topped by a half inch, grey or brown spine.
, the most common type, has narrower, yellowish green leaves (less than half an inch) with edge filaments, while var treleasei
(which may be a hybrid) has greener leaves up to one inch across and no edge filaments; this is found only in a small area of south Arizona, in the mountains north of Tucson. Schottii flowers form right along the stalk (spicate), while those of treleasei are somewhat branched (paniculate).
Both varieties are somewhat rare and are protected; var treleasei is listed in the highly safeguarded category. Var schottii may be seen in such locations as Saguaro National Park
, the Santa Catalina Mountains
and the Santa Rita Mountains.