21. Agave havardiana Trelease, Rep. (Annual) Missouri Bot. Gard.  22: 91, plates 84–86.  1912.  
Havard agave  
Plants acaulescent, sparsely suckering; rosettes usually solitary, (4–)5–8 × (5–)10–15 dm, rather open.  Leaves ascending, 30–60 (–70) × 15–27 cm; blade glaucous-gray to gray-green, not cross-zoned, lanceolate to broadly lanceolate, rigid, adaxially concave, abaxially convex; margins straight, armed, teeth single, well defined, (5–)7–10 mm, 1.5–2 cm apart; apical spine dark brown to gray, subulate, 3–5(–10) cm.  Scape 2–7 m.  Inflorescences paniculate, not bulbiferous, dense; bracts persistent, lanceolate, (3–)5–10 cm; lateral branches 12–20, slightly ascending, comprising distal 1/2–2/3 of inflorescence, longer than 10 cm.  Flowers 21–48 per cluster, erect, 6.8–9 cm; perianth yellow to yellow-green, tube funnelform, 14–22 × 15–22 mm, limb lobes erect, slightly unequal, 18–24 mm; stamens long-exserted; filaments inserted irregularly ca. mid perianth tube, erect, yellow, 5–6.5 cm; anthers yellow, 25–30 mm; ovary 3–4 cm, neck constricted, 2–8 mm.  Capsules short-pedicellate, oblong to obovoid, 4–5.7 cm, apex beaked.  Seeds 6–7 mm.
Flowering summer--early fall.  Gravelly to rocky, often calcareous places in grasslands, desert scrub, pinyon-juniper, and oak woodlands; 1200--2000 m; Tex.; nw Mexico.
Agave havardiana hybridizes with A. lechuguilla to form A. × glomeruliflora, with which it may also hybridize.