Question: When I turn over the vegetable garden in the spring I remove all rocks and stones, but by next spring more have returned. I swear they propagate during the winter! If not, why is my rock pile getting bigger each year? Where do they come from?
Answer: Rocks and stones are constant problems in northern gardens from Maine to Montana. While they may seem to grow and reproduce, it is the frost heaves of winter that push them upward through the soil.
Late-fall rains and melting winter snows seep down through the topsoil into the subsoil and around cracked stones, rocks and boulders. When this water freezes and expands it creates a pressure greater than two thousand pounds per square inch. Under such pressure the fractured and fissured rock materials crack apart, forming new stones and rocks. Repeated freezing and thawing of the soil sorts out these various-sized pieces and moves the larger materials upward.