On the edge of parks and public spaces, gardens sometimes struggle to define their edges. Things comes drifting in (including people, sometimes) and the tendency to enclose or wall with high hedges of fences or trees and shrubs can be nigh-overwhelming. But then of course there tends to be rubbish accumulation on the boundary -- drinks bottles in hedges, graffiti on walls. The boundary, private to public, subject to tiny, constant incursion.
The approach here, where the park railings have been left to stand and the garden simply set to drainage-friendly gravel and blocks makes the same firm statement as a modern bus-stop; if you drop rubbish here, it will be obvious. Behave, act with respect, because you are fully observed. Garden as panopticon.
But along the border, a softening frill of poppies and marigolds. A sudden smile in the tidiness, an effusion of bright colour saying; yes, tidy, but also yes - garden. See my flowers!
I have a terrible time with marigolds in my garden. Slugs strip them in days. And there's a practicality here, too - slugs aren't going to get out here. The marigolds will like the warm soil under the weedproof membrane. They'll both take care of their own planting. And above all there's the sense of pushing back - a tiny incursion of garden coming out into public space.