I am not sure -- sometimes you hear about people being told to cut the main
root a little short to help control the height of the tree -- but I am not
an arborist and just don't know. Pecan trees have tremendously long
roots -- a little longer down than the height showing above ground. I have
transplanted a lot of saplings -- most I do not get all of the root. Most
whether I get the root or not, do not take, but some do. I am pretty sure
that whatever root you do leave will just die off.

You might try transplanting that one and seeing if it takes before you dig
up the smaller one so you have the smaller one to try again with if the
larger one doesn't make it.

As to planning inside the easement, personally I would plant it just inside
your fence because occasionally they do go through and "clean" out
easements.

--
Marta
(if you email me directly you need to remove the X )