A leach field is the area where your septic tank drains its contaminants. It may sound unsanitary at first blush, but planting over a leach field is beneficial for your septic tank as well as the plants planted above it. The plants keep the septic system functioning well by removing water from the field and preventing erosion. And the plants benefit from the steady supply of water at their roots. Plus, plants planted over a leach field can cover up an otherwise ugly and smelly eyesore.
Choose the right plants. Look for those plants that have shallow roots. The pipes running under your leach field may be as close as 6 inches below the surface. Ideal plants include drought-resistant turf grass and native wild flower varieties that do not need a lot of water. Do not plant or eat any edible plants over the leach field.
Put on gardening gloves and clothes that you will only use for gardening on the leach field. Cover yourself from head to toe to avoid coming into contact with any harmful organisms in the soil.
Till the soil to a depth of 3 inches using a garden rake or hoe. Roots tend to grow along the path of least resistance and only loosening the top few inches will encourage plant roots to grow out rather than down.
Plant the seeds according to the directions for the species, or remove nursery-grown plants from their containers, dig holes for them that are the approximate size of the container and then plant them.
Water the area with a sprinkler for one hour. After that, do not water the plants again unless there is a drought.