Plant propagation

A weekly blog present by a Kephas landscaping & Property maintenance services, a Calgary based year round landscaping, tree services, snow removal company:

Except when handling bare-root trees, the tree should never be lifted by the stem. Because small, fibrous, absorbing roots are easily broken, the root ball must be handled carefully. Place the tree in the planting hole gently and check to see that the trunk flare will be deeper than the soil grade. 

In certain climates or conditions (such as asphalt or sidewall reflecting light and heat), thin-barked species, such as maple (Acer spp.) and beech (Fagus spp.), are susceptible to sunscald. If practical, the tree should be oriented in the hole so that it faces the same direction as it did when it was dug.

It is highly recommended to backfill around the tree with the same soil that was removed from the planting hole. Research has shown that soil amendments do not assist in tree establishment and growth unless the soil at the site significantly restricts root growth. 

Abrupt changes of texture within the soil profile can have a profound effect on moisture flow due to the possible creation of an interface between the site soil and the fill around the root ball. If the planting site's original soil is not conducive for root growth, extensive soil improvement procedures should be adopted to provide a gradual transition and make soil texture around the root ball as uniform as practical. 

When finalizing your planting, work the soil around the ball and water to minimize air pockets. Large pockets of air can allow the roots to dry out. Firm the soil around the bottom of the root ball so that the tree is vertical and adequately supported. The remainder of the backfill should only be tamped slightly as the hole is filled. 

A regular and effective irrigation schedule is crucial for new root development and establishment. Water thoroughly and slowly after backfilling. Especially in sloped sites, the remaining soil is sometimes mounded into a dike or berm beyond the outer edge of the root ball to collect water over the root zone. The photo on the top shows an "irrigation bag." These zippered bags work as a water reservoir with holes on the bottom that allow the water to slowly dispense into the root ball of transplanted trees. 

Transplanting a tree involves the additional procedures of digging and preparation for moving. Adding to that, some species are easier to transplant than others. Because digging a tree for transplanting can remove as much as 90 percent of the absorbing roots, species that have a lower transplant tolerance should be moved only when conditions are optimal.  

If extra care is taken, some trees can even be moved during the growing season. When trees are dug from a nursery field, they may be stored in a protected holding area to be hardened off.

New root generation may begin if stored long enough. Also, some leaves may drop due to reduced water availability, which can reduce transpiration.

In general, the best time to transplant most tree species, in temperate climates, is in the early spring or fall. Many deciduous plants can be moved just after leaf drop, when the moisture level in the soil is relatively high and the soil is still warm. Transplanting at this time gives the roots a chance to grow and begin to establish before the ground freezes. 

Some plants are more easily transplanted in the spring before budbreak. Transplanting dormant trees reduces demand on soil moisture because transpiration is minimal. Evergreen trees are also more easily transplanted while dormant. 

Very large trees sometimes are moved in the winter when the ground is frozen. Heavy equipment used around the tree will do minimal damage to the surrounding area. If the outer 4 to 6 in (10 to 15 cm) of the root ball are frozen, it will be easier to move without damage.

Frozen root balls require less wrapping, are more cohesive, and are easier to handle. Sometimes, the tree can be pre-dug and thoroughly mulched before the ground freezes. The hole at the new location should also be prepared before freezing.

The techniques used in digging vary little with species, size, and soil type. The procedures described here are for digging and transplanting large trees. The techniques are similar for smaller trees, which are easier to transport.

With advance planning, it is possible to greatly improve the chances of survival and increase the rate of establishment. This may be accomplished by root pruning the tree in question. Root pruning is the process of pre-digging a root ball to increase the density of root development within the final ball. 

The digging process severs existing roots and stimulates fibrous root growth. Root pruning may be repeated multiple times before the tree is actually moved.

Before moving the tree, it may be necessary to tie as many of the branches as possible to prevent them from breaking during transport. When securing the branches, care must be taken to avoid damage to the bark. Potential tissue compression or limb breakage may result from tying the limbs so tightly that a sharp bend is created. 

When digging a tree for transplanting, the size of the root ball is traditionally based on tree caliper. Tree caliper should be measured 6 in (15 cm) above the ground line, for trees less than 4 in (10 cm) in diameter. Trees more than 4 in (10 cm) in diameter are measured 12 in (30 cm) above the ground line.

For trees 8 in (20 cm) or more in diameter, a rule of thumb for the width of the root ball is 10 to 12 in (25 to 30 cm) in diameter per inch (2.54 cm) of trunk caliper. Thus, an 8-in (20-cm) tree should have a root ball that is 80 to 96 in (2 to 2.4 m) in diameter. 

The depth of the root ball may vary with the root growth of the tree. Root growth is deeper in certain species than others. Also, drier soils tend to cause deeper rooting. In general, a root ball depth of 30 to 36 in (76 to 91 cm) is sufficient. Depth can be less for smaller trees or for trees that are not deeply rooted.

The first cuts around the perimeter of the root ball should be made with a sharp spade or shovel. A clean cut is necessary to avoid tearing or breaking the roots. If the ball is being dug with machinery such as a backhoe or trencher, the initial ball should be dug several inches larger than the final ball size.

The shaping and final cuts should then be done by hand. As larger roots are located, they can be cut with loppers or a saw. Some recommendations call for sterilizing tools with alcohol or bleach before cutting to minimize the risk of transferring disease. While digging the trench, avoid standing on the root ball; the edge of the ball could break down and damage the roots.

Once the ball has been dug to the desired depth, it can be shaped. The ball should taper on the sides, slanting inward toward the base. 

A root ball with a 9-ft (2.8 m) diameter at the top might measure 6 to 7 ft (1.8 to 2.1 m) across at the base. The ball should stand on a pedestal of soil for shaping and burlapping before it is undercut. 

Place burlap on the sides and across the top of the ball. Pin the burlap together using nails, taking tucks to pull the burlap snug. The burlap should cover the full circumference of the root ball, with a bottom skirt of burlap hanging over the pedestal. Pin this skirt of burlap to the ball after the tree is taken out of the hole.

For additional support, large soil balls should be drum-laced with rope. The rope generally used is 1/2 in (1.27 cm) manila or double strands of four-ply sisal. Two loops are tied at the top and bottom of the root ball. These loops are connected through a series of weaves and tightened to stabilize the root ball.

Care must be taken not to let the rope cut into the trunk of the tree. Very large trees are sometimes boxed on site before moving. 

The tree can be undercut once the root ball has been laced and secured. Large trees must be removed from the hole with a crane or other mechanical device. Chains or large slings are placed around the ball and attached to the crane hook. It is important that trees are not lifted by the trunk because doing so can cause trunk injury and serious damage to the root ball. Cables may be attached to the trunk for additional support and balance. Once the tree is out of the hole, the burlap should be fastened to the bottom of the ball. 

When transporting a tree to the planting site, measures should be taken to protect it. The trunk should be well padded to protect from injury. The crown of the tree may be loosely wrapped with burlap to minimize drying and/or wind damage. Antitranspirants may be applied but should not be considered a substitute for adequate watering. Keep in mind that special permits may be necessary to transport large trees on public roads.

A tree spade is a mechanical device used to transplant trees. It encircles a tree and forces several large blades diagonally into the ground, forming a root ball. The blades can make clean cuts through the roots unless the roots get caught between blades. Mangled roots can be severed cleanly after the tree is removed from the hole. The tree is lifted hydraulically from the hole and can be transported vertically or tilted. 

Tree spades are available in various sizes. No attempt should be made to transplant trees larger than the size limitations of the spade. Although larger trees can be removed from the ground, transplant survival is not likely because the size of the ball must be proportional to the tree size.

Centering the tree spade around the tree will provide a more uniform root ball containing the largest possible amount of root system. In sloped sites, the frame should be supported on the downhill side.

If a tree spade is used to dig the hole, it should be dug no more than six hours before planting, or it should be kept covered and moist. Also, an attempt should be made to place the tree in the new location with the same orientation it had in the original site. 

Tree spades are often used to dig planting holes. However, holes dug in moist clay soils with tree spades tend to be glazed on the sides, which can inhibit root growth into the surrounding soil.

It is best to eliminate the potential for trouble by using a hand tool, or other cultivation tool, to break up glazed surfaces before planting. This method loosens the soil around the ball and helps eliminate any gaps that could allow roots to dry out.

If tree spades are used for transplanting, care must be taken to obtain a vertical root ball. Planting on a slope can be a problem because the ground level will be different from the tree’s original site.

A point that cannot be overemphasized is the importance of matching a tree and its requirements to the planting site conditions. The best-known planting procedures will not save a tree that is poorly suited for its site. The tree must be able to tolerate site conditions such as wet or dry soils, space limitations, or shade. Selecting a species that meets the site requirements is one of the most important factors in influencing the success of the tree.

It is important to select a tree that is healthy and vigorous. When selecting trees, examine the entire tree, especially the root ball. 

Survival and new growth are dependent on water absorption capacity and stored carbohydrates. The amount and condition of the roots in the root ball greatly affect transplant success.

Bare-root trees are usually small and easy to transplant. Because there is no soil surrounding the root system, they are lightweight, which reduces shipping costs and facilitates handling at the job site.  

The root system of a containerized tree is surrounded by soil or a substrate that is held within a container. Not all containerized trees are container grown; often, bare-root trees are established in the nursery and then sold in containers. Many trees are balled and burlapped in the nursery. In this process, trees are dug, with a portion of the root ball remaining intact, and wrapped with burlap. 

The most vigorous root growth occurs near the surface. Root growth from the lower portions of the ball is often reduced due to inadequate soil drainage and aeration. This should be taken into consideration when digging the planting hole.

Ideally, the planting hole should be two to three times the width of the root ball at the soil surface, sloping down to about the width of the root ball at the base.

The most common planting mistake is planting too deeply. The planting hole should never be deeper than the distance from the trunk flare to the bottom of the root ball. Planting too deeply can occur unintentionally because containerized and balled-and-burlapped trees often arrive from the nursery with soil too high over the primary structural roots.

Most of the time, it is best to backfill around the tree with the same soil that was removed from the planting hole. Usually, soil amendments are neither necessary nor recommended. After placing the tree in the planting hole, work the soil around the ball, then water to minimize air pockets. Large pockets of air can allow the roots to dry out. Firm the soil around the bottom of the root ball so that the tree is vertical and adequately supported. The remainder of the backfill need only be tamped slightly as the hole is filled. 

A regular and effective irrigation schedule is crucial for new root development and establishment. Water thoroughly and slowly after backfilling. Especially in sloped sites, the remaining soil is sometimes mounded into a dike or berm beyond the outer edge of the root ball to collect water over the root zone.

This has a been a weekly blog present by a Kephas landscaping & Property maintenance services, a Calgary based year round landscaping, tree services, snow removal company.

(information and images cited from ISA study guide)