You can inject over and over in the same place as long as the tree bark is firm around the WedgeChek during the growing season. Multiple or annual treatments can be made without injuring the tree. Why? The xylem is not damaged. There is no compartmentalization or sealing off of the area. When you use drilled plugs (The Wedgle does not use any drilling), it forces material/chemicals under high pressure through the defense walls in a tree causing additional damage and energy waste. Drilling wounds cause permanent damage. And our direct injection system does not damage the tree.