I have used several methods to mark plants and to make maps. Here is the link to a thread I started several years ago where I talk about Bed Maps:
The thread "How do you map your beds?" in
Daylilies forum
When I first plant new daylilies I like to use plastic knives. I bought a huge box from Costco and wrote on them using a paint pen (sharpies did not last and pencil would not write on the plastic). I have since bought some Eon markers and used them on some of the established beds. I had intended to use the laser printed labels on them, but never got around to it.
A year and a half later I decided to just go ahead and do something else as the markers were doing me no good in the garage.
I just wrote the name on the plate using a china pen. We shall see how well that lasts. I made them Spring of 2012 and so far they still look great. The china marker has the added advantage that the writing is easily removed using a bit of oil on a rag and some elbow grease.
Here is one of the plastic knife markers which I also use on seedlings.
The seedling
This is one of the Eon markers I wrote on with the china marker. It has the name of the plant, the letter/number designation I gave it for internal ID (W7) and the bed location (FLU F22). You can also see the old plastic knife marker that I just left in place when I added the new one. Like others here, I always try to take a picture of the plant marker then a picture of the flower to make it easier to label the photos when I get around to it sometimes months later.
Here is the whole plant with the marker.
Close up of the flower.
Molino Pink Loveliness 5-4 -12 FFO
Here is the bed map for that bed. It is called the Front Left Upper Bed or FLU for short. Molino Pink Loveliness is in row F position 22.
This is the bed on 5-11-12.