We all operate within certain conventions, but we can't control everything. Sometimes we smell and look like shit. Gas gets passed and pimples unexpectedly come. We can accept all of these things so long as they are maintained. Once maintenance ends, subversion begins.
Weeds are the horticultural equivalent of a zit.
They represent a breakdown, either a failure or refusal to fight the perfunctory battle against entropy. One weed is a forgivable blemish. Overgrowth is hopeless abandon. Overgrowth inside is the cultivation of abandonment, a rewriting of rules. The celebration of failure.