A. odora and A. x calidora are so similar that, even for me, it is like telling twins apart. Yet I can do it because calidora is one of my babies. However, those two can be told apart from macrorrhizos very easily, especially if both are blooming. Odora/calidora blooms have a matte look, the spathe does not flop back on pollen drop and blooms, overall, appear bluish-green, while blooms on macrorrhizos don't have the matte look, usually are longer/taller, and the top part of the spathe flops down when it is time for pollen drop. Bloom odor is somewhat pleasant on odora/calidora while on macrorrhizos, it is somewhat pungent and unpleasant.
Mature leaves on macrorrhizos have no leaf tissue between the "ears" (where the petiole joins the blade) while odora/calidora have leaf tissue between the "ears". This rule only works to distinguish these two groups; it won't hold up for other Alocasia types as there are non-macrorrhizos types with no leaf tissue between the "ears".
Hope this helps,
LariAnn
