I bought a planter four years ago and planted it with a mint, and some thyme. The thyme didn't take very well, and withered away. The mint, discovering that it didn't have an entire garden to conquer, died out of spite.
Over time, wall lettuce moved in, as it will everywhere. Not so fast, I said, and plucked it out. Then I more or less ignored this little blue ceramic-bound world. And look what splendour came of that!
A pair of fern gametophytes found their way in, and bumped into each other. And then a seed or two of Heuchera arrived. Lo and behold, attractiveness! My garden knows better than I do what goes where.