Mexican Pepperleaf (Piper auritum Kunth)

The canonical substitute for pepper leaves that is widely used even in México are avocado leaves, but only Mexican avocado types (Persea drimy­folia) have scented foliage; avocados from other regions are mostly Persea americana with insipid leaves.

Curiously, many Mexican cookbooks targeted to an English audience suggest this substitution and argue with the potential toxicity of pepper leaves. Indeed, their safrole content is rather high and not completely without risk, although Mexicans don’t care much about it. Yet scented avocado leaves contain exactly the same chemical, and thus offer no health advantage: If they are as fragrant as the authentic pepper leaves, then they are as toxic, too.

See sassafras a­bout the po­ten­tial health hazards of safrole. Besides in P. auritum, safrole ap­pears in several other neo­tropic pepper species. At least one of them, Piper hispidi­nervium (syn. P. frangua­num), is cur­rently grown in Brazil for extrac­tion of safrole (pimenta longa). Black pepper contains only traces of this toxic substance.

In the case of Mexican pepper, actually both inter­preta­tions would make sense: The inflores­cence con­forms to the botanical defini­tion of ear (it is compact along one stem), and the leaves blades have two large lobes directed back­wards which is com­monly refer­red to as eared (thus, all heart-shaped leaves are eared). As can be seen from the Latin species epithet auritus, the latter meaning is the intended one (the other meaning of ear would be expressed by spicatus in Latin, from spica ear (of grain), from Proto-Indo–European spei sharp).

I cannot explain the Spanish name hoja santa sacred leaf; maybe this hints at cultic use of this plant in Aztec rituals. The English name root beer plant is motivated by the olfactory similarity to sassafras, which is used to prepare the US softdrink root beer.