For once this is a question I can answer personal experience. Diabolo Ninebark seem to be very responsive to planting in both the spring and the fall. My wife did some backyard landscaping and the end result was a line of Diabolo Ninebarks that will be a background  for some smaller, lighter colored plants, yet to be selected, and a property line divider.

We planted some of the ninebarks in early fall and the rest in early spring. All the plants are faring well and leafing out with their distinctive dark colored leaves. In 4 to 5 years the plants should form a beautiful border between our backyard and the commons area we border. Sometimes the commons area is not well maintained during the summer months, probably a budget issue. I surmise the commons area will not be any better maintained this year with the high cost of fuel impacting all budgets.