Thanks Christopher!

One last question: I think I’ll be spacing everything about 18inches apart, but how far back should I put the center of the plants that will be the edge of the bed? The bed surrounds a culvert and borders the lawn, and there’s no hard edging dividing the two ... likely don’t want spillover bc of lawn mower..,

The distance the center of the plants should be from the edge of the bed should be at least half, if not the full height/spread of the mature plant. Both Prairie Dropseed and asters are on the floppy side end of season and that is what you want them to be able to do.

This is the bed where I’ll be placing the plants ... u shaped beds but not equal widths (about 6 feet across on the yard side at its widest). Any thoughts on arranging the trio? I’m leaning toward white salvia for the third plant since I already have it on the property...

Asters are gorgeous and hardy. Too many things like to eat echinacea. I love the white ones but they struggle in my garden. Another great plant is "obedient plant" Physostegia. Most photos you will find of it online are pink but ours are mostly white.

I do like asters! Researching options. I have an obedient plant that I was trying out but it didn’t do well with neglect (have a new baby, so not much gardening last summer). Wonder if it’ll hold up in that culvert bed (street side, s exposure). Also considering white salvia which I already have and can divide (to get started at least).

Either way, am trying to decide arrangement of the three plants...any ideas appreciated