False Aloe (American Aloe; Rattlesnake Master)
Perennial with a large basal rosette of soft, fleshy, flattened, sword-shaped leaves. Flowers in a loose spike atop a long, leafless stalk; greenish yellow, to 1 inch long, tubular, 3-lobed, tepals fused at the bases, stamens protruding. Fragrance like Easter lilies. Blooms June–August, sometimes to October. Leaves in a basal rosette, fleshy, dark green, sometimes with reddish-purple markings, lanceolate, pointed, with fine teeth along margins. Fruit a round capsule.
Similar species: There are 3 species of Yucca in Missouri, and they are relatives of false aloe. They have leathery leaves, and their tepals (petals and sepals) are free, not fused at the base.