I planted vinca minor, aka periwinkle, all over my
yard. It has beautiful, blue spring flowers that are striking against all the daffodils. I don't think it's poisonous because I've seen
deer eat it. It grows well in shade and sun, and pretty thick, with little to no
irrigation, so it's a great ground cover, attractive even when not in bloom. And I've had no problems with invasiveness here in Utah. So maybe it's more ornamental than useful, but there is something to be said for soothing the soul as well as the belly, right?