Love the map idea. My yard is really small, but my brain's capacity to remember the new ones is fading fast.
Mapping would help. I leave on the stretchy plastic label from the supplier, have some EON markers, and do remember where the older, unlabeled ones are planted. Juli, the facedown idea is good, too. Much of my Sharpie names on the EONS have faded. Fortunately, most still have enough to tell and I can overwrite with a #2 pencil. Then, make maps, maps, maps...