Pl. Life 18: 71. 1962.
Bulb nonrhizomatous, broadly ovoid, 4–7(–9) × 4.5–6.5(–8) cm; basal plate 1–3 cm; neck 4–6 cm; tunic grayish brown. Leaves deciduous, 3–9, erect, (2–)3–6.7 dm × (0.8–)1.5–3.2 cm, coriaceous; blade bluish green to deep green, narrowly liguliform, broadly channeled, margins hyaline, apex acute, glaucous to slightly glaucous, or not glaucous. Scape (3.5–)4.5–7.5 dm, suborbiculate, glaucous; scape bracts 2, not enclosing flower buds, 4.5–5.5 × 1–1.5 cm; subtending floral bracts 3.8–6.1 cm × 5–10 mm. Flowers 2(–3 rarely), opening sequentially, mildly fragrant; perianth tube green, robust, 6–10(–12) cm; tepals slightly ascending to long-spreading, greenish white, 8.8–16 cm × 4.5–9.5(–11) mm; corona white with faint green proximal eye, funnelform, gradually spreading in time, shortly tubulose proximally, 3–4 × 5–6 cm, margins between free portions of filaments irregularly dentate; free portions of filaments inserted on flat sinal base, slightly incurved, white, 2.8–4.5 cm; anthers 1.5–2.5 cm, pollen yellow; ovary oblong to pyriform, 1.5–3 cm × 10 mm, ovules 4–8 per locule; style green in distal 1/2, fading to white proximally, (13–)16–20 cm. Capsules subglobose, shortly beaked, 3.5–4.5 × 3–4 cm. Seeds obovoid, 1.5–2.2 × 1.2–1.5 cm. 2n = 38.
Varieties 2 (2 in the flora).
Hymenocallis henryae is being considered for federal protection. It has received the highest endangerment ranking by the Florida Natural Areas Inventory (Gary Knight, FNAI Director, pers. comm.) and is known only from scattered localities in Liberty, Gulf, Bay, and Walton counties. It is readily distinguished in the field by consistently having two flowers per plant and long, pale green tepals radiating from the base of a white, funnelform staminal corona. The erect, liguliform leaves vary in size and glaucousness over its range (G. L. Smith and J. N. Henry 1999).
Hymenocallis henryae was designated “H. viridiflora” by J. K. Small (1933). This name is listed as number 10 in Small’s key, but as a result of a clerical error (C. V. Morton 1935), species number 10 was described by Small under the name H. rotatum Le Conte. Even if Small had applied the name H. viridiflora to the description, as he evidently had intended, that name still would be invalid, since it would have been a later homonym of H. viridiflora (Ruiz & Pavón) R. W. Wallace from Peru.