I've been growing trees from seed for awhile now. I thought I would share one method.
I want to preface this by saying, this isn't the only method of doing it, and it isn't the only way I do it. It's just A way.
I started some seeds between two pieces of damp paper towel in a plastic bin. I wait for them to sprout, and then plant in peat pots. After they have been up and out of the soil for a day or two, I move them outside in almost full shade under another plant. As soon as they start to get their true leaves, I move them out so they start to get a few hours of early morning sun. I usually leave the tree in the peat pot until the first roots start coming out the bottom. After that, I move them into 1 gal root pouches. I'm going to let them air prune in the pouches for a year or two before planting out, unless they are very fast growers. Some trees I planted this spring are already air pruning pretty well. They may go into the ground this fall to over-winter.
I have some trees that I planted directly into pouches. I generally don't do that anymore for a couple reasons. I have had times when I planted a tree, didn't wait long enough, and planted another seed. That, of course, ended with two trees in one pot. It's also more space effective to plant in peat pots until I know which trees are going to survive.
Jay, the pouches and info can be found here: Root Pouch According to the site, they are made from recycled water bottles and natural fibers, whatever they mean by that. They make a big deal of keeping the plastic water bottles out of landfills, which seems a little disingenuous to me. You can plant directly in them, and then the plastic part, however large or small that might be, is in your land, or you can wait until your tree fills the pot with roots and remove it before planting the tree, in which case you are still going to throw it away. If someone comes up with a material that is all natural, I'll switch to that. Until then, these pouches do a great job of air pruning and making healthy trees.
According to the site, they are made from recycled water bottles and natural fibers, whatever they mean by that.
My concern exactly. This spring in an effort to get my squash off to a good start, I made several of the pots in the picture below out of "organic coffee sacks" from a local Fair Trade company. The sacks are treated with some sort of oil, but I'm not sure what else. I tried using coir pots, but they didn't seem to let the roots through as quickly as I'd like. This is my first year, so I can't give you a report on the plants (which I know got off to a bad start due to weather weirding... sigh...) or how quickly the pots decompose or allow the roots through. Also, although what I made is firm enough for the ~4" diameter and 4 1/2" height, I don't know if they'd upscale to the ones pictured on the homepage of the link you provided which is why I wondered how large the one was that you showed. I did see pictures of the Root Pouches inside a plastic pot which might be a solution.
I know that in a perfect world, seeding the trees straight into the ground has much to say for it, but I've got very limited sunshine, so I need to adapt my approach to what I have to work with!
They make those pots up to really large sizes. Mine is only one gallon. The largest I believe are 90" across and 24" deep. Mine are only 6" or so across and a little deeper than that.
I grow lots of trees from seed in the ground as well, but I have much more control over everything this way. I have random trees popping up all over the place from squirrels or something moving them, places I just stuck a couple extra seeds in, what have you. I have a couple osage orange trees popping up in a place I know I didn't plant them. I don't have any others anywhere nearby, so they didn't come from others I planted. I don't have any mature ones dropping seeds. I've never seen an osage orange growing here. I just accept it as a pleasant surprise, but for the numbers of trees I am starting, I need more control than I get from planting in the ground.