Rachael Brooke
Phillips-Rooks District Extension Agent
Agriculture and Natural Resources
While it is still technically winter, the days are gradually getting longer and home gardeners are likely counting the days until spring. In this article, Dr. DeAnn Presley, Soil Management Specialist for K-State Research and Extension, answers the question, can you place a garden on top of a septic system.
Septic systems, also referred to as onsite wastewater systems, treat and cycle wastewater back into the environment. There are many different kinds of systems, but except for lagoons, all depend on dispersing partially treated wastewater called effluent into the home’s lawn through a network of pipes called the drainfield or absorption field. Soil organisms, such as bacteria and fungi, play a critical role in decomposing the chemicals, compounds, and other organisms present in the wastewater. For this process to proceed efficiently the soil profile needs to be aerobic, meaning that the soil isn’t permanently saturated. That’s why systems have the large footprint that they do so that water can be spread out across the dispersal field so that there is not any one spot overloaded with water.
Because of all this water, plants are very beneficial for removing some of this water from the lateral field through transpiration (water moves from the roots and exits through the leaves). However, the very best plants for covering wastewater system components, such as the septic tank and the absorption field, are lawn grasses and other ornamental plants with a shallow root system.
There are a few reasons for this. It’s best to keep the area around the septic tank free of major landscaping or objects because the tank needs to be accessible for occasional pumping. Plants with large roots, such as trees or shrubs, might cause damage and/or plug either the septic tank or lateral lines with roots. From a human health perspective, vegetable gardening isn’t recommended. According to the EPA, “It is not recommended to plant trees, shrubs, or vegetable gardens on the drainfield. Tree and shrub roots can ensnarl and damage drainfield pipes. Vegetables can potentially be exposed to sewage effluent and be unsafe to consume. Native grasses and ground covers are the most appropriate planting over your drainfield.”
Because there’s always a risk that a septic system might malfunction, it’s best to avoid consuming vegetables that could have been in contact with effluent.
For more information, please contact the local K-State Research and Extension Office.
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