Sand - Above or Below Landscape Fabric?

cannonball 4/25/2016, 8:45 am

In building my first Square Foot Garden, I am using 10" high cedar. Having read the entire SFG book, it says that only 6" of Mel's Mix is needed, and if the box is taller (like my 10"), then to put sand as the first bottom layer...so that the top of the soil is about 1-2" below the top of the box. I plan on putting down Landscape Fabric (as per "This Old House" garden guy) to prevent/minimize weeds.

With this setup, should the sand go ABOVE or BELOW the Landscape Fabric?

**sanderson** 4/25/2016, 11:39 am

Cannonball, Most of my beds are 10 1/2" finished height and have 7" of Mel's Mix with 2" of chopped straw mulch to slow surface evaporation. Three rows of 2" x 4" = 10 1/2" finished height. No need to use a sand filler for just a 10" bed. Now, if the beds are in a slight depression with standing water, an inch or two of sand with the weed fabric on top of the sand would be good. Otherwise, in the heat of the summer, the extra depth to allow mulch is a good thing. In Fresno, it gets to 100+ for several days in a row.

What say others?

Zmoore 4/25/2016, 1:11 pm

IMO, only 6" is "needed" and/or that's the minimum. As Sanderson says you may not even need the filler.

However, MM is expensive, so I'm not opposed to using "filler". My suggestion would be to put the sand on top of the filter fabric. My thought is that any plants roots that extend down below the 6" of MM could extend into the sand and maybe get some more water, maybe even some nutrients that leech out of the MM. Little extra growing room for carrots and such.

IMO it depends on the filler material. If I were using a rocky soil and/or one that has a bit of clay material in it, fabric goes on top of that IMO. Sand is a little "neutral" IMO, I don't think it would hurt the plants if roots got in it and over time with pulling weeds or plants out or digging into the mix to plant, if some of the sand is pulled up into the MM I don't think it would hurt it.

My two cents.

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Sand - Above or Below Landscape Fabric?

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