Way better than popsicle sticks
If you are like me, and plant numerous seed trays, you need plant tags to know what’s planted in which tray. I have marked on the trays, marked on the cups (crossed out and re-written too), written on paper and taped it to the side, and have used popsicle sticks.
Popsicle sticks are abundant in my house. Why not recycle them as plant tags? Am I the only one who’s noticed their size has gotten smaller and smaller these past few years? They’re narrower and a good bit shorter. Once damp, they also tend to quickly turn black, which is counter-productive if you want to read what you’ve written on the tiny part that will actually be above ground.
Why didn’t I think of this sooner?
I have the answer! It’s cheap, easy to do, clean, and you probably have this in your house right now. Mini blinds! Yes, those cheap kind that are made out of vinyl and are usually too long for your window. If you have slats just sitting on your window sill, your blinds are too long. They are serving no purpose, and are making the blind heavy to pull. Did you know that you can cut them to the correct length? It’s super easy, and there are numerous videos on You-Tube about it. (Here is a link to one with a good description.)
These useless slats make the perfect plant markers! Most are white or off-white, which is another plus. Cut several from each slat easily with scissors. I trimmed mine to a point. Make them as tall or as short as you want. Need to label something with a long name like Magenta Rhododendron? No problem. Cut a tag to fit the name. They are easy to write on with pen, pencil, sharpie, crayon, etc. and are uniformly wide, so all your trays will look nice and neat when you give seedlings to your friends. Here are a few photos.
Trim mini-blinds to correct length for your window. 
Cut up the left over slats like this. 
Free tags.