Taking Place In The Trees

Dave Leonard from Lexington, KY, manned the root forensics station at the September 10 MAA air-tool workshop at Elm Bank.  He used an Air Knife to excavate the root ball of a 4″ caliper red maple that was showing signs of decline.

Turf provided the only competition for this tree, but it was showing dieback and early fall color at the MAA workshop. Dave Leonard excavated at its base to take a look at its rooting habit for possible problems.

With soil blown away from the original root ball, it was clear that the tree’s planting had initiated some problems — parts of the wire basket appeared at the edges of the root ball, and cut root ends had sent out an explosion of fibrous roots that turned back toward the trunk.

Root ends cut during the tree's digging in the nursery sent out masses of fibrous roots, quite a few of which turned back toward the trunk. The interface between root ball soil and surrounding soil can inhibit root growth into the surrounding soil; removing burlap, removing the wire basket, and breaking up the root ball soil, particularly at the ball's perimeter, can help promote the spread of new roots. Note the soil line some inches up the trunk flare; removing soil above the trunk flare will also benefit the tree and lessen its stress.

Dave cut away the roots that he could not redirect outward, and trimmed off the roots that had begun to circle the trunk flare’s base, which would otherwise eventually girdle the trunk and major anchor roots.  Some of these roots were the beginnings of a secondary root system put out by the tree in response to its stress.

Removing the worst of the inward-growing and circling roots improves the tree's chances for survival.

After excavating the root ball, Dave intended to continue to blow soil out away from the root ball, creating a shallow crater  out at least to the tree’s dripline.  Removing turf from that zone would eliminate plant competition for soil moisture; the addition of 2-4″ of mulch (kept away from the trunk) would help the soil retain moisture and an even temperature, add organics to it over time, and lessen the chance of soil compaction that inhibits soil/air gas exchange.

Dave said that he would also consider lifting the tree a few inches, to bring its trunk flare into a better relationship with surrounding grade.  This tree had been in the ground for a couple of years; Dave suggested that tree lifting might be worth doing within two to four years of planting, but could be detrimental to the tree after that.  (The window of opportunity for lifting a tree would be a lot wider if an air tool were used, rather than a Bobcat or excavator, as the tree could be bare-rooted and set back in place with relatively little stress from the process.)

Demonstrating arborist at this station:

Dave Leonard, Dave Leonard Consulting Arborist, Inc., Lexington, KY