Here's the best idea I can think of.

Take a border( like straw bales, cinder blocks, old palats, siding, etc)

and make a circular( or whatever shape RAISED BED AROUND THE TREE. )
Keep in mind this might be a temporary border, so old wood or bales will work best)

Next, fill the space under the tree inside your border with tons of shredded leaves, grass clippings, anything and everything that can be composted ( AND MIX ALL INGREDIENTS)

Next, sow some clover or other green cover crop. and thrown in a can of red wrigglers for good measure.

by next year you have a beautiful soil area to plant, and the worms will have found the bed and decomposed the nutes down to the trees roots.

There's otherways to do this, as in having topsoil or bags hauled in. But it's best to do a thick lasagne bed( around at least 1 to two feet high) and get the soil for free.

Hi Homer,

You're situation sounds similar to what I had a few years ago. Here's what I did on beds I wanted to plant in right away. Since I hadn't started composting my own materials yet, I bought bagged compost and worked it into the area where I wanted to plant. It was tough at first because my dirt was compacted like bricks due to the clay soil. I just dug, chopped and weasled until it was plantable.

Then I covered the area with shredded wood mulch. The next year, I had a little of my own compost to use so I raked back the wood mulch (there was still quite a layer) then added some compost around each plant (not right up to the stem) and then pushed back the wood mulch.

This year I wanted to take some plants out and put some different ones in and I was pleased that the ground was a lot easier to work and that there were about 10 times more worms in the beds in just 2 years.

Anyway, this is how I did it. Probably not the most efficient but it worked for me.

Val

Your soil in Oregon will most likely be clay and near the coast will also most likely tend to be acidic. Start your soil improvement program by contacting the Oregon State University USDA Cooperative Extension Service about a good, reliable soil test for base nutrient load and soil pH levels.
After this has been done dig in with these simple soil tests to see what you currently have and for a guide to what you need to do to improve that soil;
1) Structure. From that soil sample put enough of the rest to make a 4 inch level in a clear 1 quart jar, with a tight fitting lid. Fill that jar with water and replace the lid, tightly. Shake the jar vigorously and then let it stand for 24 hours. Your soil will settle out according to soil particle size and weight. A good loam will have about 1-3/4 inch (about 45%) of sand on the bottom. about 1 inch (about 25%) of silt next, about 1 inch (25%) of clay above that, and about 1/4 inch (about 5%) of organic matter on the top.

2) Drainage. Dig a hole 1 foot square and 1 foot deep and fill that with water. After that water drains away refill the hole with more water and time how long it takes that to drain away. Anything less than 2 hours and your soil drains too quickly and needs more organic matter to slow that drainage down. Anything over 6 hours and the soil drains too slowly and needs lots of organic matter to speed it up.

3) Tilth. Take a handful of your slightly damp soil and squeeze it tightly. When the pressure is released the soil should hold together in that clump, but when poked with a finger that clump should fall apart.

4) Smell. What does your soil smell like? A pleasant, rich earthy odor? Putrid, offensive, repugnant odor? The more organic matter in your soil the more active the soil bacteria will be and the nicer you soil will smell.

5) Life. How many earthworms per shovel full were there? 5 or more indicates a pretty healthy soil. Fewer than 5, according to the Natural Resources Conservation Service, indicates a soil that is not healthy.

Here is a link that might be useful: OSUCES

Be careful digging around or piling too much on the roots of those doug firs because those roots need to breathe. Also, be sure not to put any mulch right up against the trunks. Try to keep it a few inches away. Compost will always help the soil, but to snuff out the existing weeds means it could be too thick for the roots. It can be thick enough to stop seeds from germinating though. At any rate, as kimmsr says, it all starts with a soil test because its hard to look at soil to see if it lacks nutrients.

tj