Phoenix oysters should work. Spruce or fir should work, especially if they weren't cut too long ago. I tried it, and I recall it not working as well as I had hoped. Some xmas trees are sprayed with chemicals to stop them from decomposing, which is a problem for a couple of reasons. Cutting off the branches is a lot of work, but the branches can help to diversify your yard botanically. Chicken of the woods should theoretically work, but I have seen them almost exclusively on larger logs, so I don't know. Maybe others can chime in.
What I meant was that I grow mostly fruit trees and leafy vegetables. Conifer trees aren't closely related to them, so the microbiology in the conifers can add to the biological diversity of the yard, thereby decreasing the likelihood of huge disease or pest patterns, and improving the soil structure.
So, John, did you mean using the branches chipped up as mulch or composted?
I had never heard about them getting sprayed but then, I live up north and decomposing quickly is not a concern.
I think if would be relatively easy to take loppers and take off the upper branches. You might need a saw on a lower branch or two. Using them as mushroom bolts sounds like a great idea to me. What diameter log would be minimum?
On the tree farm where we went to get our tree, some trees had been shortened right in the field and there were sections of log just laying around.
Furthering Permaculture next to Lake Ontario.
I cut off all of the branches and just used the log. Usually, logs that are 3 to 8 inches in diameter are recommended, so usually a bigger tree is better. They tend to be bigger at the base than at the top of course, so one would have to take an average. I cut off and distributed the branches around the yard. The log seems to have been inoculated but I can't verify that it is with the Phoenix oysters I drilled it with. I wouldn't use Cedar (Thuja-Juniper), redwood or pine. Aromatic oils fight fungus. I would and did use fir more than douglas fir, and I think spruce should be fine too. Most mushrooms won't grow well on conifer so check the species you're trying to grow.