Peppermint is hardy to Zone 3, but invasive. In Minnesota, you can plant peppermint in a weather-resistant container and sink it into the garden to its rim. Leave this over winter. You can harvest leaves throughout the growing season, or cut the plant back to just above one or two sets of leaves, just before the plant flowers (flavor is best then). Do this up to three times per growing season; it will grow back. You can dry or freeze the leaves, as well.
Peppermint is hardy to Zone 3, but invasive. In Minnesota, you can plant peppermint in a weather-resistant container and sink it into the garden to its rim. Leave this over winter. You can harvest leaves throughout the growing season, or cut the plant back to just above one or two sets of leaves, just before the plant flowers (flavor is best then). Do this up to three times per growing season; it will grow back. You can dry or freeze the leaves, as well.