I picked up a plastic blind at the thrift store for less than a dollar (I don't buy soda and rarely water bottles). I cut the blinds in the lengths I wanted, cutting one end into a "V" for easier insertion into the soil. Sharpies always fade. Use a thicker lead pencil, or oil based paint pens for something more permanent. I still have a lot of the blind left. I also removed the cord and salvaged most of that and cut the blinds into even lengths which are stored in a box in the garage.
