Over the years, I have purchased and tried many plant markers in my garden. The two main problems are:
1. The marker becomes unreadable.
2. It breaks (I have broken many markers pushing them into the soil).
My solution is simple, but you have to make your own. I use 4-foot fiberglass electric fence posts from Tractor Supply, which I cut into 9.5-inch rods, tapering one end for easy pushing. I make the labels using a Brother P-touch label printer, which I attach the laminated tape label to the rod.
These markers last a long time and they are unbreakable (you can use a hammer to "push" them in).
Another advantage is that you can make the marker as long or as short as needed. For example, I use the entire 4-foot pole for my dahlias. As an added benefit, the marker doubles as a plant stake.