I grew four Mountain Mint plants from seed in 2003.  In late summer of that year I discovered that they had disappeared, probably either eaten or trampled by groundhogs.  I thought they were goners.  In the spring of 2004, three of the plants emerged.  They grew rather quickly.  They didn't produce many flowers their first year, but we'll have to wait to see what they do this year.  When I was cleaning up the garden at the end of the year, I discovered that the foliage gives off a pleasant spearmint fragrance.