Growing mint in a pot in the ground

I live in Toronto. I’ve been reading online and watching some videos that recommend that we plant mint in a pot and then put the pot in the ground to stop the mint from spreading. I like the idea but…

Indoor mint and sage – leaves turning black

My mint growing by the window in my sunroom (facing west) started having leaves turning black (looked burnt and dry like charcoal) on the tip. I tried watering more but it didn’t seem to change.  Actually, something similar is happening…