There are three groups in OC, two non-native Agaves, two Chlorogalums, and Hesperoyucca. Agavaceae are perennial,  from bulbs or rhizomes. Flowers are bisexual with 6 perianth parts (collective term for petals and sepals or tepals of a flower; from peri = around, anth =  anthers. Clarke), in two petal-like whorls.  There are 6 stamens often with wide, succulent filaments.

Species comparison: Hesperoyucca whipplei L, Nolina cismontana R

Santiago Tr. Tr., 2-28-13. © Ron Vanderhoff.

Santiago Tr. Tr., 2-28-13. © Ron Vanderhoff.

Santiago Tr. Tr., 2-28-13. © Ron Vanderhoff.

SE Los Alisos and Vista del Lago, MV, 12-25-13. © Ron Vanderhoff.