Through a little horse trading I came across a flat or 2 of (trident and Jmaple) maple seedlings.  I don't have room to plant ~100 seedlings in the ground, so I'm working on developing interesting stock, in pots, that could in the future go into the ground if/when I get access to a larger patch of ground.

One of my more recent experiments involves up-potting the seedlings from their 36-cell/tray homes into a 4" pot.  I prune the roots, but only as much as is needed to accommodate the other part of the experiment.  After the seedlings are root-pruned/teased I put them into the 4" pot and spread the remaining roots out.  Then slip a 5/16x1 1/2" washer over the seedling (taking care not to destroy (m)any buds) and situate it firmly around the lower trunk ABOVE any roots.  I prefer to pot the washer deeply enough that any roots forming above the washer aren't in danger of drying out.

The idea being the roots that are there now (which were pruned/teased) will sustain the seedling and cause it to grow as would be expected.  At some point the seedling's growth will swell over the washer and ideally cause roots to form.  Those roots are then guided laterally from the washer in place.

Nice project, I think you'll see some nice results in the near future. 

Dave

It works, variation on the original- done with cuttings through drilled tiles. I think Matt O does it this way as well, I have done a bunch, they always sell faster than I do them.....

John