Plants and Septic drain fields
We recently moved from Virginia where the VCE has a handout regarding growing on drain fields. I was not able to find a similar document on the Delaware CE site. Where could we find guidance/recommendations for growing/not growing (specifically veggies that fruit above ground) on top of a leach field? Thanks! Larry
I have looked at the Virginia recommendations (http://pubs.ext.vt.edu/426/426-617/426-617_pdf.pdf) and also at some fact sheets from other states' Cooperative Extension Services: University of Nevada (http://www.unce.unr.edu/publications/files/ho/2007/fs0732.pdf) and Clemson (http://www.clemson.edu/extension/hgic/plants/other/landscaping/hgic1726.html). The Virginia factsheet is the only one that gives guidance on what vegetables to grow or not grow. The others state that growing vegetables on a drain field is not recommended. The Virginia fact sheet mentions that the bacteria and viruses that you do not want in your vegetables can move more easily in sand than clay, so you should certainly take your soil texture into consideration. All of the factsheets give numerous reasons why it is not a good idea to grow vegetables on your drain field (you may damage your septic system with tillage, possible contamination of your produce, supplemental irrigation can interfere with the function of the septic system).
In addition to the above reasons, there is some evidence that bacteria which cause human disease can be taken up by plants and grow and reproduce inside the plant without any apparent effect on the plant. (Such bacteria are termed "endophytic".) Washing will not remove these bacteria from produce.
The three factsheets linked above all contain some recommendations of ornamental plants that can be planted on a drain field. The Clemson factsheet has the most specific recommendations on this front and most of the suggested species will grow well in Delaware.
I hope this is helpful. If you would like more guidance, I suggest that you contact your County Extension Office and talk with one of the Master Gardeners.