It has the characteristics of lemon balm / mint, with square stems, but it doesn't have the lemon / mint smell. Also, its leaves seem to be more rounded, where lemon balm leaves have more of a pointed tip.
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gardening.stackexchange.com is also a very good source for identifying plants. If you move this question to that stack, please include the location of the plant. – B540Glenn Apr 18 '19 at 15:22
This looks like American Cornmint to me. If you still have access to the plant, pinch one of the leaves and you should be able to smell if it is a mint or lemon balm.