My local council provided some free native grasses which I've used near the corner, so as to keep the view line clear for traffic.
Elsewhere I've used cuttings, or donations from neighbours who were cleaning out plants from their gardens. I've got some mint growing, which others can take. Lavender in spring attracts a lot of bees.
To get started, we banded together with some others converting their verges too and hired a turf cutter for a day.