The first step was to find my "hardiness zone for flowers". That turned out to be 6a (south-east Michigan), but already judgment was called for. Our winters (like the one just past) can be fairly harsh and long, so I think hardier zone 5 plants would be better.
I always loved Cosmos and think they would look great in my two empty spaces:
But when I checked the zone it turns out they need a warmer climate. Plus, they are annuals, and I already have a lot to do so prefer perennials. But I also love Foxglove, Lupine, Salvia and Snapdragons. Wouldn't a group like this be grand?
Well, that might be overdoing it, but at least I have some suitable names to research in the greenhouse.
GROUND COVER, FLOWERING AND NOT
Next I reviewed some types of ground cover for my zone. I have always admired ornamental grasses so they were the first. Some can grow to 4 feet, but 18 inches seems about right for me. That would be Pampas Grass, another of my favorites. And Miscanthus would be good, too.
I considered vines, but they are too flat and take too long to cover. But the plants below might work. They are flowering perennials that spread to hug the ground.
Very hardy perennials which also make great jam. Worth considering!
Such a lot to choose from and truly not much time. Stay tuned -
Suggestions are welcome in Comments below. Thanks for visiting and helping me think through this.