I realize it might be hard to identify this plant since it's still so young, but thought I'd give it a try anyway. The stem is mostly maroon/red, and the veins are light green. The leaves and stem are slightly hairy. Thanks!!
Flowers are key to mint IDs - post back when it blooms and we'll be able to help you out more. Right now all I'd be confident in saying is that it belongs to the Mint family.
Four Mentha species are cultivated around here M. aquatica M. pulegium M. requienii M. suaveolens Of those it looks most like M. aquatica.
Mentha aquatica. Common name water mint is a bog/ stream side species. It is also very hairy on the leaves. Other name is Mentha hirsuta(= hairy. )The original pics just do not look hairy enough. http://en.wikipedia.org/wiki/File:Mentha_aquatica_(2005_09_18)_-_uitsnede.jpg http://en.wikipedia.org/wiki/Mentha_aquatica Shimakaze, please do as Lorax suggests and add pics of the flowers.