I should have been more specific on the soil quality -

When I dig up a sample and squeeze it, it clumps up very tightly and does not break up easily, even though there is little clay content. That tells me the bark content has mostly broken down but there is not enough bacterial action to give the soil structure. I also see few worms in these areas.

In my lawn which is old soil, when I dig up a soil sample, I see the soil has "structure" meaning it is clumped up into balls with lots of air spaces even though it has a high clay content and has moderate traffic. The first time I saw this it was sort of an epiphany of what healthy soil should look like even w/o lots of organic content. It's my understanding that the bacteria secretes sticky substances that cause this clumping effect. Of course the high root density may have something to do with it.

Is my thinking at least somewhat correct?

When you scraped off the native soil, you made a huge change in the local environment for plant roots. In your situation, I would buy a load of topsoil and use this as mulch in a specific, marked area of the garden, for 2 or 3 years, and see how things go. It sounds like you are trying to grow perennials in pure compost. There might be a few species that can thrive in this environment, but I suspect that most of them need the mineral content of soil as well as the fiber you are providing.

Alex, I just finished reading the book, "Teaming with Microbes". I think that book would answer your questions and others that you haven't yet thought of.

The authors of that book assert that wood-chip mulch is preferable for perennials because the wood-chip mulch fosters fungal soil. The fungi work in the root zone to assist the plant's growth. Fungi also help soil structure in a manner similar to the one you describe with bacteria.

The book describes techniques for making compost tea to help establish various types of microbial activity in the soil.

I think the jury is still out on why wood chips are hard on annuals, but without needing to know why, you already know the what, and that should be good enough; don't use un-composted wood chips in annual garden beds.

I am lucky to have a nursery nearby that provides bags of humic shale ore. My soil is alkaline clay and the humic acid amendment conditions my soil very nicely. I use heavy amounts of it when I establish garden beds.

This year, for the first time, I was digging through my first garden bed and found hordes of young worms. The soil has a marbled black/brown look and is organized in the peds, the 'balls with lots of air spaces' effect. Originally, my clay soil was a tan color, very hard when dry.

It sounds like you need more native soil, so you could buy big bags of horticultural sand.

Although I'm no expert, I think the mineral content issue is debatable for 2 reasons -

1. I have seen studies that showed that plants can pull minerals from bark as necessary for good performance. I may have the paper if you are interested.

2. Potted plants, which include many perennials, do well in potting soil which never has any mineral content. The disclaimer here is that most people probably repot every 5 years or so since the potting soil decomposes to 50% of initial volume.

3. Nurseries often use pure composted bark to grow plants because it's cheap. They buy it raw and let it sit in huge piles for a year or more.

Nevertheless, I agree in the sense that if I had to do it all over I would include topsoil in my initial beds mostly to reduce settling (raised beds settled about 4" in 4 years) but I did not find it at the bulk material suppliers so I went with "planters mix" from the bulk supplier. I could never get a straight answer on what was in this but I suspect one of the components is builders sandy loam.

Anyhow, my plants are doing fine except for clematis, which I just realized have chlorosis. I only use "natural" fertilizers which of course are only natural in the sense that the nitrogen source is not synthetic (usually bone meal or similar).

Also, try as you might, I don't think you can ever avoid getting less than 10% native soil in a situation like this unless you put a barrier down. I mixed the amendments throughly as I added them which picked up the native soil.

Thanks for the book recommedation,

I looked for books on soil science once and only found ones based on lore or highly scientific textbooks for farming.

I did the jar test - still waiting for it to fully settle but the composition(texture) looks good, like loam.

However, I'm really interested in the "structure" which is defined here -

http://www2.ville.montreal.qc.ca/jardin/en/info_verte/fertilisation/structure.htm

I don't think my soil has much texture, especially below 6" or so. But this may take years with constant addition of organic material.