The "Autumn Joy" variety of Sedum (nobody calls it Stonecrop) is a reliable fall-blooming perennial.  It begins forming flower heads in August.  The green buds are very attractive all by themselves.  When the buds begin to open in September, they are a very light pink color. During this time, the flowers give off a sort of vanilla scent, and are buzzing with bees.  The flowers slowly darken to a salmon color, eventually turning red.  My plants grow about 2½' tall.  If the flower stems bend down to the ground, it means the clump is too large, and needs to be divided.  Dividing sedums isn't one of the easiest things to do, but it must be done about once every three years.  This variety is touted as being a good butterfly plant.  You will often see pictures of it in catalogs covered with tortoiseshell butterflies.  We don't get any tortoiseshell butterflies where I live, and I have only seen three butterflies taking nectar from it since I've planted it.