Garden over drainage field

NDgal(4)March 17, 2013

I have a large garden, but it never seems to be big enough to plant everything:). I'm thinking about creating a second garden area over the drain field of our septic system. Is this a good or bad idea? I was thinking about planting herbs and maybe a few other things in this space. The space would get full sun in the day and maybe shade later in the late afternoon/evening hours. It depends how close I plant it to the tree rows. Any herbs or veggies I should avoid in this location? The grass grows like crazy in this area.


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nc_crn should never plant over a septic field because all of the soil there serves a purpose. The soil/field is part of the septic system...the filtering and water it holds (and how quickly it dissipates it) is important to the effectiveness of the system.

Keeping the field from evaporating/drying out and/or adding more moisture to it by putting a garden on it can cause a septic system to operate improperly...from backup to stuff coming up to the surface, etc.

That said, some people use their septic system with low frequency or their field area is so large that they can garden over it.

Either way, most people advice not growing root veggies and washing any leafy/non-fruiting stuff grown there (like lettuce/chard/etc) if you're going to grow anything.

    Bookmark   March 17, 2013 at 11:01PM
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tishtoshnm Zone 6/NM

There are a lot of differing opinions as to the safety of vegetables growing over the leach field. To me though, the biggest question came down to what happens if growing the wrong things there damages the leach field? Generally, leach field problems can be described as kaching, kaching, kaching. I know that I absolutely would not have the possibly tens of thousands of dollars to repair it if something went wrong so I just assume that it is safer to find another way. Good luck to you.

    Bookmark   March 17, 2013 at 11:26PM
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We harvest the grass clippings off of our septic field for mulch, and sometimes grow pumpkins/winter squash along the edge of the drainage area and let them run. No cultivating or digging there, though. Non-disturbance is our policy.

    Bookmark   March 18, 2013 at 5:57AM
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A lot can depend on how deep it was dug. I had a new system put in last year and my plumber said it wasnt a problem to grow things over it. Stay away from things that develop major root systems, like trees and some shrubs, certainly. I have a couple of raised beds and a couple of trellis arches for cukes or beans, that over lap the drainage field area.

Ask the people who put it in for you.

    Bookmark   March 18, 2013 at 7:04AM
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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

I can only reiterate what others have already said. Generally it is considered a bad idea because of the damage it can do to the system's ability to function correctly. If system problems develop as a result of the garden then not only do you lose the garden and risk ground water contamination and run-off issues but the problems can be quite expensive and time consuming to repair.

A raised bed in that area can prevent some of the issues but not all. And deep rooting plants and root vegetables should be avoided at all costs.

Bottom line - let the septic system do its thing and put the garden elsewhere.


    Bookmark   March 18, 2013 at 10:11AM
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gardenlen(s/e qld aust)

g'day val,

i reckon it is a good use of resources, after all why let the grass have all the fun, we have been told by council what we should grow, canna lillies, lomandra various strong grasses, so we are going to plant corn our melons next season and looking at planting spuds as we don't dig to plant them, but tomato's for sure as well.


Here is a link that might be useful: lens instant potato patch

    Bookmark   March 18, 2013 at 3:05PM
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"after all why let the grass have all the fun"

Grass roots to a depth of 2-3 inches and works like a wick for pulling moisture out of the ground (part of how a septic field works). The grass also keeps your field from eroding.

It's not "having fun"'s helping the system do it's job. The fact that grass over a lot of fields looks rather lush when it's only pulling nutrients from 2-3" of soil via upward movement of water/nutrients says a lot about a field and the job it does wicking moisture from the septic output into the field.

Putting a few low-water/low-shade/low-intensive plants on the field (or preferably on the border of the field) probably won't hurt much, but if your septic field can't handle what stresses you're adding to it...especially if it blocks water transpiration while you're adding more water to the field to grow could get ugly.

It all depends on so many things...your field size, how much you use it, the type of soil in the field, how well it transpires water on it's own, what and how much you plan to plant on it, and a hand full of other things.

It's important to remember that the field is part of the system. It's "just dirt and grass", but it serves as much of a function as the tank.

This post was edited by nc-crn on Mon, Mar 18, 13 at 16:00

    Bookmark   March 18, 2013 at 3:56PM
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wertach zone 7-B SC


I don't see a problem with it.

I work for the local sewer system. I am certified in biological waste-water treatment, so I know a little bit.

The drain field will most likely be very deep, except close to the septic tank.

Some annual veggies/herbs do develop deep root systems. But they are annual, so they would not clog your system. They will rot away. The "bugs" in a properly operating septic tank will insure that possess.

Perennial herbs and veggies have a very slight chance of causing problems. Trees can be a big problem.

As far as toxins are concerned, the chances of getting toxins and other bad things from a drain field are lower than having an animal crapping in your garden. We all know that happens on a regular basis.

The soil is a good filter. That is why most, but not all well water is safe, the soil filters it. The well water that isn't safe is normally polluted with toxins from other sources than sewer.

We use sand to filter our waste-water at our sewer plants. It is almost drinkable after that process. I haven't tried it intentionally, but have had it splash in my mouth! LOL

    Bookmark   March 18, 2013 at 4:44PM
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Thank you all for the information. It has given me a lot to think about. I would never think of planting a tree or shrub in this area due to the deep roots and potential problems.

    Bookmark   March 18, 2013 at 7:34PM
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