Abstract: Described herein is a magnetic dendrometer having a frame, a spring-tension mechanism, and a magnet for moving together with the spring-tension mechanism. A magnetic sensor is attached to the frame. The magnetic sensor senses the linear motion of the magnet. This linear motion translates to trackable fluctuations in magnetic field. The magnetic fluctuations are converted to electrical signals by the magnetic sensor. A spring is attached to a free-floating wishbone-style component. The free-floating wishbone-style component is coupled to a slider which has an adjustable, single-contact point with a target (e.g., a vine, a branch, etc.). The frame is a stationary frame that carries the magnetic sensor. The frame connected via the spring to the wishbone/slider combination cooperates with each other for providing linear motion to extend or contract the spring in length directions. The length variations of the dendrometer spring are converted to linear motion of the magnet and then into electronic signals.