A few years ago we had a rental property owner that asked us plant his four window boxes and pation planters. It was fun job to do, the first three times that summer. Yes, 3 times, because it was a dry summer and nobody was watering them regularly. Finally, in late August, he asked us again. There was very little available to purchase and plant because the summer plants were gone and the fall plants hadn't arrived yet. 

We came up with an almost maintenance free alternative.