Cut it, then CODIT: The inner working of pruning
Pruning is an essential part of woody plants in our landscapes. Trees and shrubs are pruned for a number of reasons: improvements in structure, removal of damaged branches, providing clearance, or simply for aesthetics. Pruning should be thought of as both an art and a science. Where art is the technique and skill used to make a proper pruning cut, the science informs how a cut is made and the consequences of pruning.
It is important to remember that pruning is wounding. Every time a tree is pruned, a tree is wounded regardless of the reason for pruning. When a tree is wounded it responds. Everyone who has every cut themselves should have a basic understanding of wound response. If you were to cut your finger, your body reacts to limit the impact of the cut. The series of responses your body goes through end in healing of the wound. Trees also respond to cut to limit the impact of a wound. However, unlike people, trees do not heal, they growth over a wound. Wounds in trees remain for the life time of the tree, even when new wood has grown over the wound.
When any part of a tree is wounded that part of the tree is dead and susceptible to decay. Decay in trees is natural process usually facilitated by fungi which breakdown the cell components of wood. Without decay the world would be over populated by dead trees (and other things). This is obviously an issue for trees in along streets, in yards and parks, which are pruned (wounded) as part of normal maintenance.
Compartmentalization Of Decay In Trees (CODIT) is terminology coined by Dr. Alex Shigo for describing the internal process trees (most woody plants) go through when a wound occurs. Compartmentalization refers to the process a tree undergoes in order to wall off a wounded area to resist the spread of decay (or disease) through the tree. Proper pruning assists the natural processes of CODIT providing maximum protection to trees.
Dr. Shigo describes four “walls” created from the biological processes of trees which service to resist the spread of decay. Wall 1 helps the trees to resist spread of decay along the grain of the wood. Proper pruning recommend not cutting through the branch collar as this area acts as a protection zone from where the grain of the branch and the grain of trunk merge. By keeping cuts outside the branch collar wall 1resists the movement of decay along the grain of the branch into the merging grain of the trunk. Wall 2 resists the spread of decay into the center of the branch; the wood that was created in previous years. Wall 3 resists the spread of decay laterally from one side of the branch to the other. Wall 4 is a barrier zone (and chemically the strongest) resists the spread of decay to newly forming wood.
Through proper pruning techniques the spread of decay into the trunk or other main branches can be reduced. The reduced spread of decay should provide a for a longer lived, healthier, and safer landscape tree.
More information on CODIT and pruning
It is important to remember that pruning is wounding. Every time a tree is pruned, a tree is wounded regardless of the reason for pruning. When a tree is wounded it responds. Everyone who has every cut themselves should have a basic understanding of wound response. If you were to cut your finger, your body reacts to limit the impact of the cut. The series of responses your body goes through end in healing of the wound. Trees also respond to cut to limit the impact of a wound. However, unlike people, trees do not heal, they growth over a wound. Wounds in trees remain for the life time of the tree, even when new wood has grown over the wound.
When any part of a tree is wounded that part of the tree is dead and susceptible to decay. Decay in trees is natural process usually facilitated by fungi which breakdown the cell components of wood. Without decay the world would be over populated by dead trees (and other things). This is obviously an issue for trees in along streets, in yards and parks, which are pruned (wounded) as part of normal maintenance.
Compartmentalization Of Decay In Trees (CODIT) is terminology coined by Dr. Alex Shigo for describing the internal process trees (most woody plants) go through when a wound occurs. Compartmentalization refers to the process a tree undergoes in order to wall off a wounded area to resist the spread of decay (or disease) through the tree. Proper pruning assists the natural processes of CODIT providing maximum protection to trees.
Dr. Shigo describes four “walls” created from the biological processes of trees which service to resist the spread of decay. Wall 1 helps the trees to resist spread of decay along the grain of the wood. Proper pruning recommend not cutting through the branch collar as this area acts as a protection zone from where the grain of the branch and the grain of trunk merge. By keeping cuts outside the branch collar wall 1resists the movement of decay along the grain of the branch into the merging grain of the trunk. Wall 2 resists the spread of decay into the center of the branch; the wood that was created in previous years. Wall 3 resists the spread of decay laterally from one side of the branch to the other. Wall 4 is a barrier zone (and chemically the strongest) resists the spread of decay to newly forming wood.
Through proper pruning techniques the spread of decay into the trunk or other main branches can be reduced. The reduced spread of decay should provide a for a longer lived, healthier, and safer landscape tree.
More information on CODIT and pruning
- http://www.nrs.fs.fed.us/pubs/misc/ne_aib405.pdf
- http://www.na.fs.fed.us/spfo/pubs/howtos/ht_prune/htprune.pdf
