analyze soil temps and drainage
fill all holes with water
measure how quickly holes drain
Low-lying spots and those subject to flooding make poor garden sites. To determine how well a potential site will drain water, it is wise to perform a percolation test. Using a spade, dig several 12"-deep holes around the site of the proposed garden (Image 1). Using a garden hose, fill all holes with water (Image 2). Allow the water to drain out completely. Refill the holes with water, this time measuring with a watch how quickly they drain (Image 3).