Q: I have built some raised garden beds that will need to be back filled before I can put garden soil in. The max depth of the bed is 20 inches. The minimum depth is about 10 inches. How deep do I need to back fill and how deep does the garden soil need to be?

A: First of all, plant roots only grow in the top 10 inches of soil so you can fill the bottom of your bed with cinderblocks or bricks or anything that you have lying around just to take up space. Fill up to ten inches below the top edge of each bed.

I guess fill dirt would be fine in the bottom but I wouldn’t want dirt that is mostly very heavy clay because it seems like that would interfere with drainage

As far as where to get your subsoil as well as your topsoil, there are several landscape material yards around the Atlanta area that will mix soil for you and deliver it.

They can mix up a nice sandy loan and add worm castings or chicken manure to make a rich soil to fill your garden beds.

You could also get the Soil3 folks to deliver their custom compost.