The corolla flares open into five lobes, two upper lobes and three lower lobes. The upper lobes are 7–16 millimeters (¼–⅜ in.) long by 4–9 millimeters (–⅜ in.) wide and generally oblong, obovate, or cuneate. The lower lobes are similarly shaped and are 7–20 millimeters (¼–¾ in.) long by 4–18 millimeters (–¾ in.) wide. The central lower lobe is usually slightly longer than its neighbors. All of the petal lobes have rounded ends. The floral tube that houses the reproductive organs and is visible at the base of corolla lobes is white or lilac in color and 4–6 millimeters (–¼ in.) long. The white color of the floral tube can extend to a variable distance onto the corolla lobes, particularly in a stripe on the lower middle lobe. The color of the corolla lobes generally varies from pink to purple, but has been described by collectors as being "purple, scarlet, rosy-lavender to bluish-purple, dark pink to lavender, pinkish-purple, deep violet-purple, dark purple, bright mauve-pink, bright purple-pink, magenta with [white eye], [and] reddish pale with white eye."Zamudio 2001, p. 184. A rare white-flowered form is also known.
