A general rule is you don't put rotting stuff near tree roots because they don't like them. I typically drop the trees unti the smallest hole I can make and then top the soil around it with the stuff to make it grow, like mulch fertilizer, etc, if I have it on hand. It's especially important if I'm encroaching on lawn so I don't mow it. I rarely use cardboard because I like ir as starter fuel, but it, like comfrey leaves can help squash adjacent competition.
Regarding the comfrey... I thought I was really smart when I used comfrey shredded as a mulch on top of most of my squash seeds. Not so much. None of those germinated. All the seeds planted were from the same packet. All seeds were planted in chufa infested ground (alleopathic). Removing the leaves and planting new seed solved that. Scrawny plants, but that is because of the chufa!
Anyhow, maybe don't mulch with comfrey until the seeds are sprouted?
That makes sense. I busted the sod today. I'm thinking of digging deep, stuffing the trench with all of the material I get from pruning and cleaning up. Maybe go over that with a good coat of the soil and doing maybe 2" of wood-chips over the top. For seeds and tiny seedlings, I find wood chips to be a pain in the rear. originally going to do air-layer beds but I've run out of time.
Thanks for the suggestion I won't put any gree stuff on top or too shallow below. I can imagine comfrey suppressing seed growth as it creates kind of a blanket. My big thing right now is planting out well so I have less of an issue with grass encroachment.
IF this was me doing this, with the materials you listed, I would:
1. set up a compost heap using wood chips, green manure and organic chicken fertilizer to build a layered compost heap. (torn up cardboard can also be used in compost heaps)
2. when you plant trees the rule is to make the hole the same depth as the roots or root ball and three times the diameter of said roots or root ball.
This gives the roots a way to expand out and gain good foot hold faster, watering in with a root stimulant (vitamin B-12 water or even some willow water) also gives the trees a jump start. don't forget to prune larger trees back by 1/3 of the branches to promote root growth over leaf growth.
3. When spring comes around your new compost will be ready to be used as a mulch layer, just remember to keep it from touching the tree trunks by at least 3 inches for small trees and 6 inches for larger trees.
4. plant the trees at the recommended spacing so you don't stress them again by transplanting (15 feet spacing, trunk to trunk works well for most trees but not pecans, they need 30 feet spacing because they will grow up to 75 feet tall).
This would be the easiest way for me to go. I wish I had access to more healthy dirt so I could create more of a mounded-effect. The bed is actually an extension of a bed that is almost circular and the rest of the bed is hugel style.. (basically a big keyhole garden.)
What kinds of trees are you going to be planting? How big of an area?
I find that dug-up sod creates lots of weeds. So I try to minimize doing that as much as possible. I also have found that grass holds moisture in the soil; originally I thought "grass is bad near my fruits/vegetables!" but I've since changed my mind, and now include growing grass in my water strategy. Grass is part of Fukuoka's "natural irrigation" strategy. I think it might help keep your nursery hydrated, trimming where appropriate.
I am not sure what to do with the comfrey and green compost. I would start a compost pile, I guess; I would not want to kill off the grass by smothering it, or feed weeds that got released from the digging. Maybe you can use it in another part of your land? Add it to existing compost, or do a "Ruth Stout" style composting? (deep 2-ft bed of material, bury the compost in it).
The bed is a starter bed for seeds and tiny seedlings. I have a five-gallon bucket full of pears from an heirloom tree that is probably close to 100 years old, I will plant all of these seeds. I'm getting shagbark and Black walnut seeds from the forest. The seedlings are Hungarian black locust.
The bed is a place to tend the trees until they put a little growth on and then I will spread them out. The bed is about 4 ft long and 20 ft wide. I already hand dug the sod out. I agree about the weeds but I need to get these planted before winter.