This spring I planted 2 Mikweeds. On one of them the leaves are starting to turn a purplish red. The other one seems fine. Does anyone know what is causing this?
If they have bloomed and seeded (with the exception of A. curassavica), then they are just starting to harden off for the coming Fall. All of its growth in one season terminates after seeding. This is known as senescence. It is completely natural, esp after a cool spell. My incarnatas are looking a little sleepy too.