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General Design -Residential Design Analysis & Planning Research in partnership with the Council of Educators it) Landscape Architecture and Landscape Journal

Communicatio Student Colla tion

Student Community Service


September 18-22, 2009 at the ASLA Annual Meeting and EXPO in Chicago

An air spade is used to excavate a 'Bloodgood' Japanese maple (Acer palmatum 'Bloodgood'), above, from its original site. The maple is lifted out of its location after being excavated by the air spade, below. Note the breadth and density of the root mass.

it would not survive the excavation and move, and it was sent to the chipper.

In contrast, the second birch was air spaded during the workshop in the heat of midday. With an eight-foot-diameter root mass, the tree was lifted by a Bobcat, relocated, and then replanted, without evidence of wilting. Two weeks later, the transplanted birch remained settled in its new location without sign of stress.

The crowning achievement of the workshop, however, was the relocation of an 18-foot 'Bloodgood'Japanese maple (Acerpalmatum 'Bloodgood'), which had grown too large for its current location.

Again, the crew hydrated the tree prior to the excavation and move. The day before the demonstration workshop, Furgal

and Foti's crews air spaded the tree's roots, sprayed them with water, and covered them with wet burlap. On the day of the workshop, a crew transported the maple by truck to Nonset Farm and placed it shortly after noon in its new location in Foti's nursery. They backfilled and welled the planting, then flooded it. Despite the hot, sunny weather and exposed location, not a single leaf on the tree wilted.

Standard Methods

Currently, arborists use two standard methods for moving large trees. Arguably, the more popular is the balled and burlapped (B&B) method, which uses a backhoe and then a fork to dig the tree's root ball, which is then tightly wrapped in burlap and drum laced for transport and planting. Some arborists double burlap the ball to help ensure its stability during transport, as roots encased in soil are susceptible to breakage when pressure is put on the root ball during lifting and moving. The size of the root ball is determined by the size of the tree and the equipment available to move it.

Alternatively, a tree may be moved by a mechanical tree spade, which is a hydraulic machine with a set of curved blades that spread to grab at a wide area of soil around a tree's trunk. As the blades descend—slicing through soil and roots—the aperture formed by their lower points closes, forming a cone-shaped root ball under the tree. The tree and its root ball are then lifted from the hole with the hydraulic arm and moved, still held by spade "bucket," to its new location. It is planted in a hole dug earlier by the same spade; the spade operator simply lowers the spade and root ball into the waiting hole, then releases and retracts the spade blades so the tree can be leveled and the root ball backfilled and watered in.

Both methods rely on the formula diameter at breast height (DBII), which allows 10 inches of root-mass diameter for every inch of trunk caliper. This ratio is considered the accepted standard for deter-mining what the minimum diameter of a root ball should be.

B&B vs. Tree Spade

When transplanting trees, an arborist's goal is to preserve the greatest number of roots within the accepted standard. The more roots that can be saved, the shorter


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