Clover seeds scattered on any grass works too. It grows along with the grass, and replenishes nutrients to the soil, lowers water needs. Bees love it too.
This is an interesting concept, it beats what I've been doing which is basically trespassing to plant trees on lots adjacent to my own. I planted about 40 on a neighboring lot and 60 on my own recently and I plan to do more.
I hope you are being careful to choose native species, or at least avoid invasive species. The wrong plants won't help anything and may crowd out important local plants.
