From clay to hugelkultur mound... ?

So my wife and I just bought what we thought would be the perfect 1/3 acre lot. She fell in love with the new house, I fell in love with the huge, unfinished backyard with it's southern exposure and potential for a nice row of espaliered apple trees along the back fence. But alas, after moving in, I spent 5 hours yesterday digging in hard packed clay. I think I only moved around about 2 cubic yards in 5 hours. The lawn will be easy - about 1/4 of the backyard will be lawn; that's the part I leveled yesterday. I'm going to bring in 4 inches of sandy loam + compost mix for the lawn, which will run me about $500. The rest of the yard is going to be dedicated to bushes and fruit trees pruned to a max of 4 feet tall. We're going to build hugel mounds on either side of the lawn and I'm wondering if I can use this clay soil to do it, since it's free and there's a pile of it in the adjacent lot, or if I should try and get a couple dump truck loads of "screened topsoil."

The screened topsoil will run me another few hundred dollars, but I've gotten it before and it's a heck of a lot better than the clay I've got next to me. The other option I was thinking would be to use the clay I've got here and amend it with green mulch from a tree service + nitrogen as I build up the mound, let it cool off until next spring, and then plan on planting in it. I'm not sure if that's something I could pull off in that short amount of time, or if it would even give me very good soil? But money is tight with all of the improvements we want to try and get done, so I thought I'd ask and see what all of you thought?

Here's my two cents worth. I recently posted this on another thread about hugelkultur and soil.

I built my buried wood beds (basically an underground hugelkulture) with no soil in it at all. Layers of organic material in the form of year-old grass/leaves/weeds/woodchips were put between the logs and sticks and big chunks that went into the piles, as well as some sand, as that's all we have here. All of this was topped with the same mix - so it's topped with about 2 to 3 feet of basically just a mulch/compost. This is what I planted into. The only soil in these beds is what went in with the transplants.

So, when you build your beds, you can just use organic matter - green mulch from tree services will work great. And you can mix some clay in there as well - it has nutrients, and great water retention, that you'll want in there. Put this stuff on and in between your logs, sticks and whatnot, to fill the spaces and get some diversity in there. And then cover it with organic matter as well. If the organic matter you put on top is really fresh, I don't know how easy it will be to plant into the first year, but by next year it should be lovely. But even this year you might be able to get a cover crop in there. It all depends on what you're using and how old it is, I think.

And in a couple of years, I bet the clay beneath the hugelkulturs will be looking fantastic, full of worms, and more like soil all the time. Should feed the hugelkultur really well.

My beds were finished being built at the end of May, and I started planting on June 3. Here is a photo of my garden from yesterday. As you can see, it's working great.

Let me know if you think this will work for you!

Cheers
Tracy