To give you an idea of how poorly tree grates can look and function, here are two examples.
The round grate is the absolute worst. The whole is tinier than tiny; the metal materials jutting up from the ground are unnatural and dangerous. It's rated A1 F1.
The one with the square base is rate okay for aesthetics: I like the simplicity of the shapes and materials. But he drainage is sorely inadequate for a big tree. So I give it an A4 F1.
