"We're getting our own homestead, depending on whether they agree to make some repairs. The house has a septic field with lateral lines. I'm wondering if it's safe to plant a garden over the lateral field? Or would it be unsafe to eat the food that's grown there? From the perspective of not having to water the garden much, it makes sense, but I want to make sure it's safe, too."As I told Liberty, I'm not a septic system expert. However, I immediately had some concerns about growing food in a drain field, and a little research proved I was right to feel cautious.
Why You Shouldn't Garden Over Your Drain Field
* I think the field would be too damp to grow healthy fruit trees or bushes. Too much moisture leads fruit trees to have disease issues.
* I also wonder if the soil over the drain field would be too high in nitrogen to grow happy plants. High nitrogen levels lead to plants with lots of leaves, but not much fruit. And if the nitrogen is high enough, it will kill the plants.
* I'm also concerned that vegetables could potentially have bacteria in them that would lead to illness. According to the Virginia Cooperative Extension (VCE), this risk varies depending upon the type of soil in the drain field. Clay soils are better at filtering bacteria and can "[eliminate] bacteria within a few inches of the drain trenches." Sandy soils filter bacteria less effectively and "may allow bacterial movement for several feet." VCE goes on to say that "A properly operating system will not contaminate the soil with disease-causing organisms, but it is very difficult to determine if a field is operating just as it should."
Why You Should Plant Over Your Drain Field
That said, planting over the drain field is considered a good idea. Turns out, the right plants can help your drain field by removing excess moisture and reducing soil erosion. But which plants are best? Dense grass is the most common drain field plant, and according to VCE, if you don't have at least that, you should plant it ASAP. If you want flowers, and the drain field is the only available space for them, plant shallow rooted plants that don't need tons of water. Plants with deep roots or intense water needs can clog the draining or grow into drain field pipes. Never deeply till a drain field and do not use raised beds, as they may prevent moisture from evaporating in the soil.
If you have limited space and really want to grow fruit in your drain field, VCE says to choose safer options. For example, shallow rooted vines (like cucumbers) work, if you keep the fruit on a trellis. They also mention tomatoes as a possibility, but I do not recommend them personally; tomatoes can have very deep roots, which could damage your drain field.
Title image courtesy of Tim Evanson.