Many of you probably do this, but for those who don't know...
Cheap plastic knives, forks and spoons make excellant plant markers. I cut the knives in half and cut the handles off the spoons and forks, with a pair of wire dykes. Write on them with a fine point sharpie and you are good to go.
I've used "popsicle" sticks before and they bleed and mildew.