Transwiki:Digging trees and shrubs for transplanting

When transplanting trees or shrubs from one location to another, digging the plant in preparation for moving it is typically the most challenging part of the job.

Anyone who grows trees and shrubs is likely at times to wish to move them. Transplanting involves digging the tree or shrub, moving it to its new location, and then replanting it. The most difficult of these steps, and the one which requires the most know-how, is digging. This article discusses digging up trees and shrubs to about 10 cm (4”) in trunk diameter.

For small plants – up to a trunk diameter of 2.5 cm (1”) or so – digging can be done with an ordinary garden spade. It is important to do it right, but the work is not difficult and the odds of success are very good. For trees or shrubs with a trunk diameter over 2.5 cm (1”) in diameter, and up to as much as about 10 cm (4”) in diameter, there are good options available which make it possible for even the home gardener to transplant successfully. Note, however, that size and weight of the required root ball, and the work involved in transplanting, increases rapidly as the trunk diameter increases. Moving trees with trunks over about 10 cm (4”) in diameter is likely to require heavy equipment and specialized expertise. The cost of transplanting increases rapidly as the size of the tree increases, although there is almost no limit to the size of trees which can be transplanted successfully if one is willing to pay the price.

Steps in digging
Digging a tree or shrub in preparation for transplanting involves several steps. Various digging techniques can be employed, but no matter what approach is used, these steps must be attended to. The information covered here includes just the bare essentials. There are many factors which should be taken into account if one is to realize the best possible results. These considerations include the species of plant being moved and its condition, the soil conditions, climate, season of the year, and accessibility of the site.

This stabilizes the root ball to help ensure that it stays intact during the transplanting process and is usually done B&B style (ball and burlap) or in a "WB" wire basket.
 * 1) Selecting the tree or shrub to transplant, and determining the size of the root ball to be dug.  An approximate rule of thumb is to use a root ball 20 times the diameter of the trunk (as measured just above the basal flare) for trunks up to 1.3 cm (½”) in diameter, 18 times the diameter of the trunk for 1.3-2.5cm (½-1”) diameter trunks, 16 times the trunk diameter for trunks 2.5-3.8 cm (1-1½”) in diameter, 14 times the trunk diameter for trunks 3.8-6.4cm (1½-2½”) in diameter, and 12 times the trunk diameter for trunks 6.4 to 10 cm (2½” to 4”) in diameter.  For most trees and shrubs, the root ball depth should be about 20 cm (8”) for a 30 cm (12”) diameter root ball, ranging up to about 45 cm (18”) for a 120 cm (48”) diameter root ball.
 * 2) Cutting the root ball free from the surrounding soil so that it can be moved.  This can be done in various ways.  For small root balls (up to about 30–35 cm (12-14”) in diameter), an ordinary spade may be used to carefully slice the root ball free from the surrounding soil.  The best spade for this purpose should be sturdily constructed, with a long, narrow blade cut square across at the tip.  Such spades are sold commercially as “nursery spades”.  Also available are the less sturdy  “drain spades” - these have long, narrow blades which are usually rounded at the tip.  Whatever type of spade is used, it is helpful to keep the cutting edge quite sharp.  Keeping the blade clean and smooth helps also.  Coating the blade with silicone lubricant or a similar product can help.Use the spade to dig a circle around the tree at a slight 15 deg. slanting inward angle. After you complete the circle, cut away some of the soil outside the circle and angle the spade into the bottom center of the rootball to cut any tap root at the bottom of the ball. If it's small ball tie a string (twine or a small strap around the top outside edge of the ball to keep the soil of the ball compact and tight. Use the spade to lever the tree out of the hole. If it's a larger ball over 16" you will need a tractor boom, a forklift or a lifting tripod in order to lift the tree out of the hole using either straps pulled under the ball or forks underneath the ball. A 32" ball will weigh 300-500 lbs. depending on density of soil and moisture content. Years ago before the 1950s all trees were dug by hand. Years ago in order to move larger trees, the nursery men barerooted the tree while it was dormant to lessen the weight they had to move. Starting in the 1950s with Vermeer in the US and Optimal in Europe, modern hydraulic truck and loader mounted spades began to be used on a larger scale. Currently modern nurseries use machine tree spades to dig more than 90% of the trees grown today as they dig a uniform ball in lesss than a minute and automatically lift it out of the ground and place it into a burlap "sock" or "pocket" that holds the dirt inside of a metal wire basket that is tied and twisted into a tight package ready for shipping.
 * 1) Lifting the root ball out of the ground so that it may be transported to its new location may take either a strong back, a ball buggy or dolly or a machine like a loader or a forklift.

Depending on the digging method used, steps 3 and 4 may be reversed.

A fast handdigger can dig 20-20 16" root balls an hour or better. A machine spade can do 30-45 an hour. The bigger the ball the more time it takes to handle the tree properly.

There are several related new tree moving/growing techniques worth mentioning:

Dr. Bonnie Appleton Phd has been experimenting at Virginia Tech's Hampton Roads Virginia Research Station with a method that  water washes the soil from the roots thus barerooting trees at any time of the year in order to examine and prune the roots for defects, (a major problem caused by the improper planting of young trees) then she washes the soil back around the roots with water to create a mud backfill whick locks the tree into the ground and eliminates air pockets in the soil. This also supplies the tree with a large influx of moisture to quickly grow new feeder roots.

Ren Heard of Lake Tree Farms in Virginia and Kentucky, uses a similar pressure washing technique combined with growing the recently dug tree in custom made baskets made of wood snow or sand fencing with more closely spaced pickets (organic pots) that air root prune the tree, eliminating circling roots (a major problem of pot growing) and allowing the tree to be replanted at anytime of the year with no transplant shock. This method is called Organic potting.

Digging table
Approximate root ball diameter to be dug Approximate root ball depth

Considerations
When transplanting any plant, preserving a significant fraction of the root system is necessary to maximize the chances of successfully re-establishing the plant in its new location. The practice of root pruning in preparation for transplanting can help concentrate the root system into a more confined area, thereby increasing the fraction of the root system that can be preserved.

In the case of trees and shrubs, the weight of a large root ball, and secondarily the weight of the tree itself, contribute significantly to the effort required to dig and move the plant.

Digging equipment
Trees and shrubs of all sizes may be dug up using simple shovels.

Conventional earth moving equipment such as backhoes and front loaders are also used.

Some nurseries use tree spades, which are specialized powered equipment dedicated to digging up trees and shrubs.

A specialized tool for cutting roots may also be used, possibly in conjunction with a leverage-based manual system for lifting the root ball.

In the case of extremely large trees, these have at times been moved by equipment designed for moving missiles.