What is a good bed liner

[mrluxenhogen]

Hi everyone,

I am building container boxes on top of asphalt and was wondering what material/product would be good to use as a liner. I want to have a barrier at the bottom of the box so the soil isn’t sitting directly on the asphalt. I am also concerned about using the most organic method possible. Are there alternatives to the plastic sheets that I have seen a lot of people use? Thanks for the help!

[DoubleDogFarm]

How permanent, semi permanent is this planter? If it will be move within a year or so, I would use a few layers of cardboard. Not sure, but asphalt may wick up through anyway? Just make sure you have plenty of drainage.

Eric

[mrluxenhogen]

Thanks for the response Eric. I've been reading various sources and a lot of people recommend cardboard as well. They are going to be permanent beds so if I used cardboard I would imagine I would have to replace it annually, right? Also, I had the same thought as you.. would the asphalt still wick up anyway?? I appreciate your thoughts.

Jared

[DoubleDogFarm]

I'm thinking you may want an air gap under your planter. A flat 2x4 will get it up 1 1/2" above the asphalt. The bottom could be semi solid made of slats. Depends on the wood used, they will need replacing in few years. If your are worried about soil leaching out the bottom, maybe coir matting. Coir is expensive and may eventually plug up. Another choice maybe burlap bags.

Eric

[mrluxenhogen]

I was actually considering burlap sacks as well. Have you used them before? Do they allow proper water drainage, etc.?

[DoubleDogFarm]

Only as compost tea bags.

I'm thinking any porous material will eventually plug up.


Eric

[CharlieBear]

Contamination, contamination, contamination. Your only real option is thick mil plastic as a liner, sorry. Paper, cardboard, etc will develop cracks in it quickly and let the patroleum products leach in. You might put pin holes in the plastic to help drainage, or better still, make the box contained. If it is permanant treat 2/4's with linseed oil and let dry. Then nail them on the bottom of the box side by side. The excess moisture will drain out and you will not have to use heavy grade plastic. That is what this environmental engineer would do.

[mrluxenhogen]

Thanks for your input Charlie. Have you used linseed oil in this way before? I've heard that it can encourage mildew growth and am worried that could lead to other problems. I definitely want to preserve the wood as long as possible if I go ahead and make the box contained.

[mrluxenhogen]

What if I just got some loose gravel and poured a 2 to 3 inch thick layer in the bottom of the planter to separate the soil from the asphalt?

[DoubleDogFarm]

Take a look at this...
https://www.puyallup.wsu.edu/~linda%20chalker-scott/horticultural%20myths_files/Myths/Container%20drainage.pdf


Eric

[mrluxenhogen]

Thanks for the article Eric. Thats great information.