Violets are the only plant aside from dandelions impervious to mulch –no matter how thick it is.
From observation, I find they’re not so strongly tenacious as weakly passive, using so little sunlight and soil nutrients they can wait for the mulch to thin. Usually growing in deep shade and root crowding of grass, asters and other prairie plants, it seems they are satisfied with not much.
It’s the ideal resume for a ground cover. Lay mulch to get rid of the mass of weeds and grass, and get a homogeneous carpet of violets. Making little holes in this carpet, I stick in my preferred plants, and the violets quickly disappear under them.
Even so covered, they stick around. If by any chance a space becomes void, the violets will fill it, keeping weeds from getting a foothold.
This way your “empty” space will still be productive; violets being an edible and medicinal crop themselves. There’s a surprising number of uses for them you might read here. In general the leaves are used to thicken soups, raw in salads, with their flowers as a garnish.
The living mulch aspect is more than enough for me to let them stick around. And although they’re easily pulled; can you imagine pulling every one out? Not happening.