Water the lavender plant well a few hours before you plan to dig it out. This loosens the soil around the plant and gives it an energy boost to survive the move.
Trim away any remaining flower stalks from the lavender plant using clippers. You can trim away as much as two-thirds of the plant without causing damage to the lavender.
Break the ground around the plant as big as the widest part of the plant. Use the shovel to cut down vertically around the plant, angling towards the center of the plant at the end of the downward thrust.
Work back around the circle, using the shovel to loosen the soil around the lavender roots. This creates a large dirt ball that houses the roots in existing soil. Pry up the root ball with the shovel gently, moving around the plant as needed, until it breaks free of the surrounding soil.
Lift the lavender plant up by the root ball, never by the plant itself. Move the lavender bush immediately to the new location, which should be a hole twice as big and twice as deep as the root ball. Place some liquid fertilizer or compost in the bottom of the new hole before setting the lavender bush gently inside.
Push in the dirt around the lavender bush root ball until the space around it is filled. Tamp down the soil gently but firmly with the shovel. Create a small mound of dirt around the base of the lavender bush to funnel water directly to the roots. Water the bush thoroughly once the transplant is complete.