Thanks Bryan.

My location is zone 6a. I don't know the grass of
the house, or whether pesticides have been applied.
I'll call the current owners and ask them.

I want to do the whole back yard, which is a lot
(I guess that was a pun). But I'll start with one bed,
then another, then another, etc. I guess I could try
doing one with the double digging technique, and see
just how horrible the experience is.

When you threw in the four inches of compost, in which
season did you do that?

And, what is "hard panning"?

I wish I had studied horticulture when I went to
college. Somebody convinced me to do math instead,
and now I'll be paying the price. Still, I can't
wait go get dirty.

bryan lafleur wrote:

Where are you located, and what kind of grass do you have?

From my understanding, double digging helps avoid hard pan layer,
which helps root formation in some plants, and helps with soil
percolation. I agree this is the optimal way to do it, but it would
have to be a very small area to be worthwhile in my opinion.

On the ones I have done, I first killed the grass (especially if it
was bermuda) then tilled the existing soil, added 4" compost and
tilled again, then built the bed and added prepared soil mix that I
get in bulk to the proper depth. Dont know the scientific benefit of
this, but my thought was to have a soil transition instead of
definitive layers, which I thought would help prevent hard panning.

Good luck,
Bryan