CO-Horts

CO-Horts

Friday, July 14, 2017

Stem Girdling Roots

There have been a couple previous blog posts on dysfunctional tree root systems but we have had a number of really good examples of trees with stem girdling roots come through our office this spring so I thought I would share some pictures of the issue.

A normal root system will grow outward from the trunk of a tree in a radial pattern that resembles the spokes of a wheel (though it will not be as uniform).  There is also normally a pronounced outward flaring of a tree’s trunk where it meets its root system. 

 Due to some nursery stock production techniques and planting practices some landscape trees develop roots which do not grow radially out from their trunks but instead grow across or around them.  

A root of this container grown oak deflected upward when it contacted the container, grew to the surface and then across the surface of the container .  When it reached the other side of the container it then began to circle. If left uncorrected such roots can become girdling roots.

The same tree also was planted deep in the container, ~4 inches of soil was removed from the top of its root ball before I found its first structural root.  




Such roots have the potential to become ingrown into the trunk as they both grow.  This interferes with the tree's vascular system which becomes compressed where it presses up against the offending root.  In cases where the root is circling and wrapped around the trunk the tree may be girdled.

Major stem girdling root on a littleleaf linden
 
Stem girdling root on the same linden  cut in preparation for removal. 


The root has been removed, note the compressed tissues of the trunk.




Deeply ingrown stem girdling root on a horsechestnut.  We were unable to remove this root but be were able to cut it at either end to stop it from growing further.

Exposed stem girdling root on an autumn blaze maple
Trees which develop stem girdling roots may have reduced vigor, slower growth, be more prone to lean and fail and are more susceptible to a variety of stresses.   Severe cases can lead to decline and death.
Swamp white oak with dieback, little growth and chlorosis 
A root collar excavation revealed the tree was planted deeply and had several stem girdling roots.
The root flare should be mostly above grade and visible.

Close up of  partially ingrown stem girdling root on the above swamp white oak

Austrian pine with leaf scorch and very slow growth. We found several major girdling roots. 

Stem girdling roots on the above pine

Ingrown stem girdling root on the other side of the trunk of the  above pine





Cottonwood which failed above a stem girdling root.
Close up of Cottonwood which failed above a girdling root.

So what can you do to prevent these issues and encourage a normal root system? 

1)When planting a tree, make sure the root flare is exposed by removing any soil or potting media covering it.
2)Plant the tree with its root flare slightly above grade.  The first structural root should be in the top couple inches of the tree’s root ball or at its surface.
3)If the tree has circling roots remove them at planting.  Shaving or boxing the root ball is a good way to do this.

"Boxing" a trees rot ball at planting to remove circling roots.

4)Dig a large planting hole which has a saucer shape.
5)Inspect the tree’s root flare regularly and remove any potential girdling roots before they become ingrown.

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