Sharpies will fade within one year. I think you are better off using a pencil if you want the label to last. The plastic labels will age and break off in about a year as well. To protect yourself from losing the name of the plant, write the name on the label on the part of the label that will be in the ground, as well as the part above ground. The ground will block UV from the sun and prevent the deterioration and fading of the plastic and information on it. When the above ground portion fades away and the plastic breaks off, you will still have the underground portion to use to id the plant and create a new label.
