even if i bought wood.. to make it last.. i would have them potted in plastic and insure there were a lot of drain holes in the wood ... so it stayed as dry as possible .. so determination of the planter size.. would be a function of the pot size ... if that makes sense ... so.. at a min.. i would be thinking about a MINIMUM of a 25 gallon black pot ... see link.. no clue if that is a good price.. i got most of mine from recycle bins .... but i dont use them decoratively ... and that one is already 25 inches wide at the top .... any even in nurseries.. plants of the size you want.. BLOW OVER.. wind and stability are going to be your BIG PROBLEM ... especially if you buy them big ... and i should also point out.. that conifers have very specific potting media issues.. and what you fill the pot with will also be very important.. and its not going to be your standard bag of potting media .... i am sure you can do it.. but i doubt you are going to find the info you need here.. with the specificity you wish .... i simply dont think us tree peeps are going to have a lot of specific info for you ... other than to list the variables .... good luck ken ps: winter storage will also be an issue .... Here is a link that might be useful: link -- you shop price.. i am just showing the pot

do you have a digital camera... take pix of what you like... and peeps here can ID specific plants... tree.. bark and leaf with bud , if possible .... what grows in the hood.. is usally a good indication of what will succeed with little or no effort on your part ... maples.. I HATE THEM ... because i garden under trees [hosta] and i like grass under trees ... you will have neither with norway/silver maples... and no garden under the rest of the maple family ... dont get me wrong.. they are beautiful trees for golf courses and neighbors lawns ... no tree needs wind protection if grown properly ... short of a hurricane, of course ... buy on the smaller side of size.. and let them grow into the native conditions ... a recent transplant.. should need staking for no more that a year or two.. and then be free range.. sounds like soil is not an issue ... roots need air as much as the tree needs water.. and therefore clay is an issue only for water retention .... try to locate a local arboretum ... such as longwood gardens.. which i think is in DE ... and visit a tree park with labels .. i seem to think they have some massive gorgeous copper beech there ... simply awesome.. and being a nut tree.. tend to be deep rooted .. compared to maples ... i am not aware of any trees that kill animals.. most of the animals are smart enough to avoid that issue.. and those that arent.. well .. darwin rules... so.. i have eliminated a couple of your worries.. variables... so now go find the trees that make your toes curl ... there is a birch .. with red leaves.. and white trunks.. said to be borer resistant ... pretty cool for a reddish color ... link below ... if zone appropriate .... good luck ken Here is a link that might be useful: click over to the images page ...

as for a tree recommendation, if you want shade in the summertime, i would personally plant a GA native, the Tulip Poplar. in addition to having the ability to grow quite rapidly, it has huge leaves that will provide abundant shade. it gets a bad rap as a 'garbage tree' from some people because of the leaves, but i personally find them to be no worse than any of my maples. the flowers in spring are great. for the 'ornamental', if you want a slow grower that is really showy in spring but will eventually get bigger and more showy over the years, i really like the Susan Magnolia. certainly, the first time you see one in spring that's blooming, you'll fall in love. you can hit Google Images and look up pictures of both... if neither work for you, it would be good to know the approximate end height you are looking for in a tree, slow/moderate/high growth rate, decidious or evergreen, flowering or non. btw - it's hard to tell from a distance, but the six green plants look like ligustrum (variegated privet) which seems to be the "lazy contractor's favorite". yours look like they could use some trimming back based on the first picture - you can literally cut them down to a cubic foot square, and they will grow back to their current state in less than 12 months (even if you take the leaves off). they're veritable weeds IMHO. :)

I think it would do far better in the ground. The roots would stay cooler and the surface feeder roots could spread. Yes, the roots are in the ground already. Redbuds are known for having a very long taproot and not transplanting well so one would think that if you are ever going to move it the sooner the better. If you do decide to do this do it during dormancy and dig deeply. Even better (and far easier on the tree) might be to remove the sides of the box and simply add a bit of soil to build a small transitional berm from ground level to the level where the tree is planted. You won't want to change the actual planting depth of the tree at all- just a bit of soil to make it look like it fits in. This is what I would do. It would not disturb the taproot and would still allow other roots to spread out.