This is pretty much ditto to my new Lantana topic. Lantana and Cosmos are my very favorite plants.
I've got some 18" Cosmos ready to go in the ground in another week or so.
Do they stay on a single stalk or will the plant branch out just a tad?
Should I plant them very close to each other, like 6"? I want them to support each other (I'll also stake them) during the wind, and I don't want any gaps between the plants.