My deep beds are 12 inches deep and everything is growing very well. I also have some deep beds that are only 6 inches deep and have corn and pumpkin and these are all growing very well too. I think Mel said that 6 inches of top-quality topsoil would be plenty for everything except for if you wanted to grow really long carrots. I don't remember him saying anything about 6 inches of hay, that is a lot of mulch. Ruth Stout's method calls for a thick layer of mulch, maybe that's where you heard about that. Although I only mulched 2 inches this year, I think that 6 inches of topsoil and 6 inches of mulch would be great as this would greatly reduce your weeding and watering.

When you get your book, remember also to refer to Mel's website for additional information.

Here is a link that might be useful: Square Foot Gardening

I think I recall a mention somewhere of six inches of hay on the bottom with six inches of soil over that. I have no idea how well it works.

Probably the "best depth" has a lot to do with cost. My guess is that six inches is good, but deeper will be (somewhat) better. How much better is up for debate, as is whether it is worth the extra cost. What I might do is build 'em 12 inches deep, but fill them with six or eight inches or Mel's mix (see his website) or equivalent, and see how it goes. That way if you have lots of extra compost someday (like I did), you can easily fit it into the beds. (I'm assuming that six extra inches of soil will cost quite a bit more than the "six extra inches" of lumber.) Of course, you'd have to make your supports sturdy enough, too. Hmmm.

One thing to wonder about, is how does the moisture retention of a six-inch bed compare to that of a 10 or 12-inch bed? I would *guess* one might have to water a shallower bed more, and the moisture level would vary more. Anyone have opinions on this?

My beds are made with 2x8 lumber, so they're 7 and 1/4 inches high, one laid over cardboard and "clayey" soil. It did well even the first year. I've often wondered how much the roots go into the clay, but don't really know.

I think putting them up on tables sounds really cool!

--Riff.

If your deep beds were going to be on the ground, I'd day definately, the deeper the bed. It makes planting, weeding, and picking all that much more enjoyable. I don't know about other people, but one of the reasons I put in deep beds is that I hate bending over to garden. Plus with high deep beds, the slugs have a harder time getting to your vegetables.

Another thing to consider is that you could make your beds 6" high, then, if next year if you really want them higher, you can make them higher by adding additional lumber on top and just fixing the new lumber to the old. This is how I made my deep beds. I made 2 squares out of cedar fence boards and stacked one on top of the other and fixed them together.

Monika, that's a sensible suggestion, about building a second layer of boards if needed! Much better than my idea!

--Riff.