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Guidelines for Growing, Installing and Maintaining Healthy Trees

Prepared by the Illinois Tree Specification Review Committee

Nursery Propagation, Growing, Harvesting & Handling:

Impact of Liner Production Practices on the Finished “Package”
(click thumbnails for full image)

Introduction
Structural Roots
Fibrous Roots
"J" Roots
Two Sided/Flat Roots
Circling/Girdling Roots
Torn/Broken Roots
Trunk/Central Leader
Branching
General

1. INTRODUCTION
In order to grow quality trees, it is important to start with quality liners. Grading is the process used to determine the quality of the liners. Sometimes grading occurs in the field. Most often grading occurs after the liners are harvested. Bare root shade tree liners should be graded for size (caliper and/or height) as well as overall quality of the roots, trunks and tops. More details follow.

2. ROOTS
Structural Roots Liners should have several lateral roots spaced evenly around the trunk to provide support so the trees don't blow over in the wind.



A lack of lateral roots can cause problems with newly planted liners as well as larger trees.



Fibrous Roots Liners should have as many small roots as possible. These roots are key to the uptake of sufficient water and nutrients. Fibrous roots can be achieved by root-pruning, under-cutting or transplanting at any stage of production. Often, root-pruning is done on bare root liners by pruning the ends off of the roots prior to planting.

 

“J” Roots “J” roots are most often the result of how the liners were planted in the field. They can be caused by a mechanical planter or wet field conditions when all or most of the roots, including the structural roots, are dragged to one side. The resulting root structure is shaped like a “J”. “J” roots may not provide enough support or stability.

 

Two-Sided / Flat Roots Two-sided root systems are most often the result of liners that were planted too close together, or liners that were left on the same spacing for too long before being transplanted. The tops of these liners also tend to be two-sided or flat.

 

Circling / Girdling Roots Circling roots are roots that grow in a circle around the trunk or around other roots. They are often the result of liners that were at one time grown in a plug or container. Circling roots may eventually kill the tree.

 

Torn / Broken Roots Torn or broken roots are often caused by the digging machine used to harvest the liners.

 

Prior to planting, these roots need to be pruned back to the point at which they were torn or broken. The larger the damaged root, the greater the potential for future problems. The liner may not be left with enough structural roots or the tear may extend up the trunk causing damage to the root crown or root flair.

3. TRUNK / CENTRAL LEADER
The trunk should be as straight as possible. The base of the trunk should not have a large pruning cut from re-growing the top. A large cut may not close quickly or properly and may provide an entry point for insects and disease.

 

The cut made when re-growing the top should not be excessively far from the major structural roots. The “shank” that results from this procedure is then minimized, producing a straighter, better looking trunk. Additionally, having a shorter shank at a consistent height above the structural roots will help to ensure that the liners are consistently planted at the correct depth, not too low or too high.

 

The central leader should be alive. If topped, there should be no canker, insects or disease under the tape often used to train the new leader.

 

The trunk should have no visible cankers and no major damage from poor pruning cuts or poor handling practices.

4. BRANCHING
The branches should be evenly spaced around the trunk without excessive gaps between the whorls. This helps to ensure that the tree will have good branching on all sides. It also allows for flexibility in pruning to the desired clear trunk height. Sometimes the branching tends to be two-sided or flat if the liners were grown too close together.

 

 

Ideally, there should be no branches around the central leader with tight crotch angles. If there are, they should be pruned out to avoid multiple leaders.

 

Some liner producers differentiate between “branched” and “light branched” liners. Light branched liners are typically defined as having fewer and/or shorter branches, most often on on one side only.

 

They are positioned as a more economical alternative.

5. GENERAL
When the liners are shipped, they are usually tied together in bundles. The bundles should be tied in such a way as to not make cut marks on the trunks or roots, or cause the trunks to be bowed. The roots should be kept moist. They should not be allowed to dry out during grading or shipping, or prior to planting. The roots, trunks and tops should be free of molds, insects and diseases. The buds should be tight and not breaking.

 Typical Two Year Liner