ya samw question I just asked on fri or sat...well I have er about 50-60% chance of getting them out and growing..but I go around to local places myself and get the volunteer JM's that would be turned into mulch if I just left them, and I can't let them do that to such a beautiful tree..anyways, i usually stick a spade down half or more of the length of the spade 2+in from the stem and then push down at an angle to loosen the dirt and pull the plant out...this is stressful to the plant thats why my survival rate is low, but i leave the ground as it was...
now since these are in your yard I would take a spade and dig them out like a normal transplant..so 3-4in from the stem make a circle with your spade by inserting it all the way in the ground or at least 6+inches in the soil..then on one or two sides dig so you can stick your spade underneith the 6" rootball and lift..if you feel it staying stuck because of the plants roots dig deeper or cut it as far down as you can, you don't want to yank it out of the ground as this is stressful to the plant..with this method you will have a close to 90% or better rate of survival..the roots of a first year volunteer are usually only 4-5" in diameter and only 4" or so deep..so with a 12" diameter rootball you shoukd be fine and have no issues..good luck to you!