I have a question about hybrids. Specifically, I'm interested in knowing about peppermint (Mentha x piperita). I have read that this plant is a cross between spearmint (M. spicata) and watermint (M. aquatica). I have also read that because peppermint is a hybrid, it is sterile and cannot produce seeds. Yet I can find peppermint seeds for sale. Assuming that commercially-available peppermint seeds will grow into true peppermint when planted, I am curious to know how the seeds are produced? If the answer is that M. aquatica is pollinated by M. spicata (or vice versa), does it make a difference which plant pollinates the other? Or is the resultant peppermint the exact same either way? And if thatâ€™s not how the seeds are produced, then what is the correct answer? Also, somewhere I've seen reference to "white" and "black" peppermint plants. Are there really such varieties -- and, if so, what makes them "white" and "black"? Or is there just one true peppermint?