Plants acaulescent, freely suckering; rosettes solitary to cespitose, 7.5-10 × 7.5-10 dm, open. Leaves erect, 76-78 × 10-11 cm; blade glaucous-green to dark green, lightly cross-zoned, lanceolate, rigid, adaxially concave toward apex, abaxially convex at base; margins straight or undulate, armed, teeth single, well defined, brittle, 4-7 mm, 1-2.5 cm apart, interstitial teeth (2-)3-7, mostly along distal 2/3 of margins; apex not conspicuously incurved, spine brownish gray, slender, 2.5-4 cm. Scape 2.7-5.5 m. Inflorescences narrowly paniculate, not bulbiferous, open; bracts persistent, triangular, 1-2+ cm; lateral branches 9-16, ascending to nearly perpendicular, comprising distal 1/3-1/2 of inflorescence, longer than 10 cm. Flowers 32-45 per cluster, erect, 7.4-8.6 cm; perianth greenish cream, tube campanulate, 15.5-20 × 15-23 mm, limb lobes persistent and often leathery during and after anthesis, spreading, unequal, 15-22 mm, apex often flushed with maroon; stamens long-exserted; filaments inserted subequally below rim of perianth tube, erect, yellow, 4.8-6.4 cm, apex flushed with maroon; anthers yellow, 17-25 mm; ovary 3.3-4.6 cm, neck slightly constricted, 4-8 mm. Capsules not seen. Seeds unknown. 2n = ca. 120.
Flowering early summer. Sandy to gravelly places with desert scrub; 700--1100 m; Ariz.
Agave phillipsiana is known from only four sites within Grand Canyon National Park. All are found on terraces along permanent waterways. Three of the sites are near pre-Columbian agricultural features or habitation sites. Two sites occur near a Kayenta-Anasazi Pueblo cliff dwelling (A.D. 1000-1150), on a terrace presumably once farmed by the early inhabitants. Agave phillipsiana possesses traits that would be advantageous to those harvesting it for food, since it is a plant that freely offsets and has open rosettes with large, long leaves that are easily cut. The species is possibly an ancient cultivar selected by pre-Columbian people from populations related to A. palmeri, A. colorata Gentry, or other closely related taxa.
