There are many differences between spearmint and peppermint plants, from the leaves, flowers and flavor of the two herb plants to their most popular uses. Each dates back 5,000 years to ancient Egypt and India, where they were valued for the effects of their oils, though those substances were used for different purposes.
While both plants are in the mentha genus, they are of different species. Peppermint is from the piperita species, while spearmint is from the spicata species.
Leaves from both plants tend to be about twice as long as they are wide and have jagged edges. However, where peppermint has its leaves growing from stems, spearmint leaves grow almost directly on the branch.
The blooms of these herbs also differ, as peppermint usually has a purple bloom while spearmint generally has a pink or blue bloom.
The two plants also have different uses. Spearmint is often used as a mosquito repellent, and peppermint is used as a mild antiseptic and decongestant.
Spearmint's flavor comes from carvone, which gives it a sweet taste. Peppermint's flavor comes from menthol, which imbues it with its distinctive cooling sensation.