I recently planted two pecan trees in my backyard (Carya illinoinensis ‘Caddo’ and ‘Kanza’). Both trees came in plastic containers, unlike how I ordinarily get my trees (usually I buy them B&B or “balled and burlapped”). My one previous experience with a container tree, a magnolia that I ironically paid to have professionally planted, died within two years. When I went to dig it out, the entire rootball came up. Basically, the tree had been completely root bound, and the encircling roots never spread into the surrounding area. After that costly experience, I have planted my trees myself.
So how to properly plant a container tree? Apparently, traditionally, one makes some vertical cuts with a utility knife in an attempt to prevent encircling roots. But most interestingly, recent research done at the University of Minnesota suggests a more dramatic solution. You “box” the tree. You cut off the sides of the root ball to form a box shape. On the one hand, it seems insane.. On the other hand, it makes perfect sense: if you cut all the encircling roots, the new roots will spread out. (See their instructional video here.)
So after taking a deep breath, I turned on my reciprocating saw and chopped off the sides of the root balls of my two new pecan trees. We’ll see what happens!