I have collected Mentha varieties for more than twenty five years and currently have a very large collection. Some varieties that I have are the result of spontaneous hybridization. Hybrization does not only occur with mints planted in pots, but also with mints planted in beds if the beds are relatively close to each other.

In my opinion this does not constitute a big problem because most spontaneously formed hybrids are easily recognized when they grow in a pot or bed of another mint variety. If you don't like the hybrid, you simply remove it from the pot.

However, do not put it away immediately but evaluate its properties. From my own experience I can tell you that sometimes spontaneously formed hybrids have very attractive properties that exceed those of their parents.

Janus