Structural Support Systems

Many valuable trees have structural defects that warrant support. Such support systems are designed to prevent points of potential failure from failing and causing irreparable harm to a tree or its surroundings.

Canopy installations aim to support weak branhes or unions. They can be installed with dynamic or static cable, depending on the case. Bracing can be used to support preexisting cracks, and props can be used to support limbs with a heavy load (most frequently fruit trees). Ground anchors can also be installed to support a tree at the roots.

Dynamic Cabling

Dynamic cabling is installed in the upper 2/3 of a canopy to support a suspicious branch attachment. Usually this is presented as included bark or an open fracture.

Dynamic cabling is made out of polyester braided rope. They have a small amount of stretch, and the cable is installed with a small amount of slack. This allows the tree to move under normal conditions, but prevent it from moving past a breaking point during wind or snow storms.

The cable is installed in 2 different sizes depending on the tree. For larger limbs (10" and larger), a 3/4" diameter rope with a breaking strength of 10,200 lbs is used. For smaller trees, 1/2" rope with a breaking strength of 5,200 lbs is used. Both cable sizes are installed with a protective sheath where the cable wraps around the trunk.

Polyester does break down in UV over time. Dynamic cabling systems are only expected to last 10 years. They should be inspected every 2 to 3 years.

Advantages of dynamic cabling:

  1. Some movement allows the tree to develop reaction wood naturally.
  2. Non-invasive installation
Dynamic cabling installed in the canopy of a giant smoketree. The largest and lowest union had included bark (a structural weak point). This cable will help this tree from losing half of its canopy in a major storm.

Dynamic cabling installed in the canopy of a giant smoketree. The largest and lowest union had included bark (a structural weak point). This cable will help this tree from losing half of its canopy in a major storm.

Static Cabling

Static cables utilize galvanized steel cable. This type of cabling is rigid and is installed with no slack. This restricts relative movement between two codominant stems. Such systems are necessary for trees with preexisting fractures and potential failure points low on the trunk.

Large trees take 3/8" steel cable with a breaking strength of 15,400 lbs. Smaller trees take 3/16" cable with a breaking strength of 3,990 lbs.

Unlike dynamic cabling systems, static sytems are permanent installations that require drilling a hole through the wood at the 2 points of contact. Static cables should be inspected every 3 to 5 years.

A preexisting fracture caused by stresses applied to included bark. Static cabling and bracing could be used in conjunction to support this limb.

A preexisting fracture caused by stresses applied to included bark. Static cabling and bracing could be used in conjunction to support this limb.

Bracing

When preexisting fractures exist it is often useful to install a threaded rod. The threaded rod helps pull the two sides of the fracture back together and it provides permanent support. Usually, the rod is instaslled just above the fracture.

Props

Props are used to support tree limbs that are overburdened, in our are this is usually most appropriate for fruit trees. A post is installed in the ground and the limb that needs support rests on top of the post.

 
 

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