Planting on a drain field

I've always been told to not let anything woody, or especially with strong roots, grow on my drain field.  Why is that?  

My septic likely won't be pumped for decades (I have it inspected every 3 years).  All the turds and pee get broken down and flow into the drain field where bacteria eat it and it sinks into the sand.  Seems like if we planted things along the drain field piping with roots that got down to the good stuff, we could use that nutrient to make food.

The roots can grow into the pipes. Clog them, crack them

If you want to grow stuff on the drain field, consider growing grasses which you can harvest for compost or mulch.

I'm pretty sure my drain field consists of what look like 18" plastic culvert cut in half.  They are like a quonset hut underground.  So I don't think they have holes in them since the entire bottom is open.  

Tyler, it's a lawn now and the grass over the leach field chambers (I looked up the correct name) isn't any greener than the grass around it.  So either the grass roots aren't long enough to reach or my idea won't work anyway.  I think the chambers are less than 3' deep...

I would think that anyone that says don't plant trees is saying for root clogging reasons.  You have to determine if that applies in your case.

If the reason is icky gicky stuff from the pipes feeding the trees,  i personally have no issues with that.

We have a volunteer elderberry in our leaching field. Soon it won't be there. The berries are larger than where it is drier, but this bush has bland, boring tasteless berries. As all our elderberries began their lives as wildlings, I can only assume this plant gets too much moisture. So, if you choose to try it out, I'd nix elders off your list of potential plants.

Mike Jay wrote: it's a lawn now and the grass over the leach field chambers (I looked up the correct name) isn't any greener than the grass around it.  So either the grass roots aren't long enough to reach or my idea won't work anyway.  I think the chambers are less than 3' deep...

Lawn roots are typically very shallow.  I was thinking some kind of tall prairie grass suitable for your region.  Prairie grasses have deep roots.

My dad bought an old home, with a similar setup. Someone had either planted or simply allowed volunteer trees, in the drain field. When he bought it, there were 3 half-grown trees, and within 3yrs, he began having plumbing issues - bad ones. After having it pumped 2years in a row, he decided it was time to find out what was going on. When they started, they found that the roots of the still smallish trees had already destroyed most of the field, within 15feet of each. I'd personally pay heed to the words of those folks advising you against the trees.

Thanks Carla, that's great info.  Do you know if his drain field was perforated pipe or if it was the semicircular chambers I showed above?  I don't know if it would make a difference but I suspect it might.

I would probably do smaller berry bushes or herbs if I planted anything at all.

I'd think that roots wouldn't have a problem turning 180˚and cruising up and through the pipes from the bottom. Or just constricting around them. Or pressing them sideways and breaking the pipe through shear. But then again, I usually make it a personal rule not to tempt fate when the consequences end up with me knee deep in shit.

I wouldn't entertain the thought of planting anything bigger than groundcovers.   Everyone I know on septic received strict instructions not to, and my personal experience with tree roots destroying terra cotta drain pipes in the city was a nightmare and thousands of dollars to repair.  Never trust a root - it will do what it wants to do!

Hey Mike,
I honestly don't remember, but if you look at any cement sidewalk, driveway, or street, even seemingly small plants - dandelion comes to mind - roots don't need holes, even on small plants, and can break through almost anything. Trees are typically more stubborn, and are definitely bigger. Bushes are smaller, but something to think about as a (very) general guideline, is that the top 'aerial' portion of a plant is most often sized and shaped very similarly to the root system. So, the bigger/thicker the plant, the bigger/ thicker the roots; the taller the plant, the deeper the roots will go; the more spread out the part you see, the more spread out is the part you can't see. Most grasses will be an exception. There are other exceptions, but it's wisest to think of roots as the wild boars of the underground - they get into everything, and will destroy anything in their path.

That said... If you really want berries, go with strawberries. Their root systems are shallow, and more horizontal, and there are plenty varieties you can choose from. Other options, beyond berries, and depending on where you live, plants with a rhizome root system might be a good option.

Ok, I guess I'll abandon this idea.  But I'll keep it in mind the next time I meet a septic plumber.  I can totally see how roots would destroy the leach fields that use perforated pvc pipes.  

Thanks for all the feedback folks!

Hubby just suggested annuals - veggies or flowers - it's a thought, and they're much less damaging. Bulbs might be another option - think irises, tulips, and crocus.

It actually amazing how many roots a tree can grow inside a pipe on a dry spell.  Its kind of crazy, but they can completely plug the line.

Would trees be ok on a leach field if they were coppiced regularly?

I'm guessing not.  Assuming a tree for coppicing is rather fast growing, I'd assume its roots are also rather strong and would be more likely to do damage.

I am a water/wastewater engineer and have designed and repairs many typical septic systems.  It looks from the picture that you have a pumped system (probably a sand mound system) where the overflow from the septic tank is pumped to the green pipes.  The green pipes have holes at 12 o'clock from which the pumped liquid shoots up and hits the black half circle then leaking into the sand where is receives treatment.  It is VERY important not to plant anything over the field that could possible send roots down into the system, the roots will find their way into the pipes and plug the system and are costly to remove.  Also, be sure to clean the screen on the septic tank, where it overflows to the pump chamber, at least twice a year and pay attention to what chemicals you are using in your house.  

One more thing, I would suggest pumping your septic tank every 3 to 5 years whether you think it needs it or not as solids will settle out and not completely break down.  When you do have it pumped be sure to have all the solids pumped out (the liquid doesn't really matter) and don't let the pumper truck operator convince you to leave some solids to keep the tank "working" there is enough bacteria in very flush to keep the tank operating as designed.

Thanks Peter!  I was hoping an official expert would pass by.  Sorry if the prior posters are also experts...

That photo was off the interwebs, not of my system.  My system doesn't have a pump, it's a septic tank with a leach field downhill a few inches from it.  I believe the leach field is made up of plastic chambers that look like smooth plastic culvert cut in half and buried with the open end down.  So I don't think there are any perforated pipes or any squirting happening.

I had the system inspected by a certified inspector.  He checked the sludge layer thickness and the scum on top along with a bunch of other checks.  He was happy with how we were doing.  He suggested that as long as he or someone certified like him checks it every 3 years, we may never need to have it pumped.

What about shallow-rooted herbaceous plants?

I am glad to hear that you get your system inspected, always a good plan.  It is hard to assess your situation without knowing the details, however, it is most likely that your drain field consists of a series of parallel pipes with two rows of holes (at 5 and 7 on a clock face) which spreads the liquid from your septic tank over the whole area of the field.  Which means that you don't want to plant anything over the field that may send roots down into the area around the pipes.  It is also important not to drive over your field or septic tank or erect any structures which might interfere with basic maintenance.

Mike,

you should be able to get a diagram with depth of the field lines from your county sanitation department. I'm in a pretty rural area, and I was able to get it. Mine turned out to be 6' down, so I drive over them all the time, the pressure at that depth is modest. Not the distribution tank, though.

I am thinking about building my greenhouse over it, since I don't need a crazy footer, and can disassemble it if I need to dig up the lines. It keeps traffic off it too. I had a couple trees near there when I moved in and I killed every tree within 40 feet. That can be a very expensive fix. The only thing allowed to grow on there is shrubs and smaller, and I coppace the shrubs every other year (they are legumes).

When I had a septic put in at a cabin I built 8 years ago they used the half culvert things.  This house's septic is about 12 years old so I assumed they did the same.  I won't plant or do anything based just on that assumption.  I do have a map that came with the permit when they installed the system.  I could dig that out.  

For now I'll just keep growing grass on it and start some herb/flower beds around the inspection ports.  They're a pain to mow around anyway.  I'll harvest the grass periodically for mulch.  I won't put trees or bushes on the drain field.

Thanks team!