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We are planting our first raised bed this year for organic vegetables/herbs. I purchased a cedar kit from Natural Yards that is 4x4 and 16.5" high. I got the taller height because don't want to amend the soil underneath due to likely contaminated soil from old railroad ties. I've read a few articles about using newspaper or cardboard on the very bottom, but the lady at Natural Yards indicated that I should use a bottom layer of gravel in my bed, then add my soil. Does anyone have any advice here about what to use as a barrier that will still allow proper drainage and what type of gravel I should use? Thanks in advance!

Tags: bed, drainage, garden, organic, raised, vegetable, vegetables

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Is the barrier for soil contamination, weeds or gophers/moles? I would get a soils test done by an ag lab to make sure it's contaminated. They are usually reasonably priced and can save you the headache of not knowing what exactly is in your soil. The gravel won't really stop anything because what eventually happens is that the soil will work it's way into the voids in the gravel, making it useless. Newspaper and cardboard will breakdown over time.

What we always did under our raised beds was put down hardware cloth to keep gophers and moles out, and then weed fabric (we had bermuda grass really bad), but for you if weeds aren't a huge issue, I'd go with nonwoven filter fabric (not weedcloth) instead. That will keep the soils from coming into contact with each other, but also allow for drainage.
You could put four to six inches of 3/4" stone (sometimes referred to as dense grade) and them a few inches of stone dust. Tamp the stone dust so it's tight and then put your loam on top of that. Once your all planted, a little salt marsh hay will keep the weeds down and the moisture in.
Thanks Rachel & Mark. I'm going to look into the soil test. The barrier is just so the "good soil" does't get contaminated by the soil underneath that I think may be contaminated by seepage from old railroad ties. To your point, Rachel, I should get a test to see if it really is contaminated. I don't think we have much of a weed problem in the area I'm going to be working, but I would also like to keep them out.

Mark - you've laid it out pretty nicely for me! Thanks. I've never heard of salt marsh hay, but looked it up and it sounds perfect! I'm hoping I can get some where I am in St. Louis.
Stacey -

You should take a look at "Lasagna Gardening" by Patricia Lanza. In her book she describes how to garden with no digging, no tilling and no weeding. She lays down layers of newsprint, etc... right on top of the soil as a barrier.

We tried this with our potato beds and in our concrete wall planters that surround our pool and it works beautifully!

Deb (debfroggie)
a lot depends on the type of material your dirt is made up of. Here in Pensacola the dirt is pretty sandy and drains well. Consequently we don't worry much about drainage. I dug down about 10 inches and that made my raised beds nearly 16 inches deep (6" framing plus the 10 inches I dug). There aren't many garden plants that go my deeper than that level so I assumed I was immune from any contamination deeper than the 16 inches. So if you don't have to worry about drainage why bother with any type barrier on the bottom? I used a mixture of self made compost suplimented with a little cow manure to fill the beds and the garden grows like crazy. I do need to water a little because the ground in the beds is so loose it allows the moisture to evaporate out quicker than a typical garden does. Mulching helps that issue after the plants are large enough to mulch.
I have a copy of the Lazagna Gardening that I will send to anyone who will pay the shipping.

Deb said:
Stacey -

You should take a look at "Lasagna Gardening" by Patricia Lanza. In her book she describes how to garden with no digging, no tilling and no weeding. She lays down layers of newsprint, etc... right on top of the soil as a barrier.

We tried this with our potato beds and in our concrete wall planters that surround our pool and it works beautifully!

Deb (debfroggie)
Is there any advice for finding non-woven filter fabric at a garden center? How do I discern between it and other rolls of black fabric-like stuff?

Rachel said:
Is the barrier for soil contamination, weeds or gophers/moles? I would get a soils test done by an ag lab to make sure it's contaminated. They are usually reasonably priced and can save you the headache of not knowing what exactly is in your soil. The gravel won't really stop anything because what eventually happens is that the soil will work it's way into the voids in the gravel, making it useless. Newspaper and cardboard will breakdown over time.

What we always did under our raised beds was put down hardware cloth to keep gophers and moles out, and then weed fabric (we had bermuda grass really bad), but for you if weeds aren't a huge issue, I'd go with nonwoven filter fabric (not weedcloth) instead. That will keep the soils from coming into contact with each other, but also allow for drainage.

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