Are you tired of plastic markers breaking? I had often used sturdy plastic knives to mark plants, but they didn't last long in our cold climate. I suddenly thought of all the used flatware at my local thrift store. Stopped by there and came home with a whole bag of sturdy stainless knives which work well to label my small hostas. Use a marking pen designed for the garden and they should last awhile before they need redoing.
A great use for shirts that you no longer need: Recycle them into garden ties. Cut the sleeves off. Then start at the bottom and cut the hem off. Then cut a strip about 3/4 - 1 inch wide (depending on how thick the T-shirt is) all the way around, angling it a bit wider as you near your starting point. Continue to cut spiral strips until you can cut no longer. Stretch the strips and roll into a ball the way you'd roll a ball of yarn.