The New 4 D’s

The 4 D’s of tree pruning have been accepted practice for years. They have been modified and corrupted over time, and are now essentially ignored by many arborists.

The earliest version recommended removing only the Dead, Diseased, or Damaged branches from a tree when pruning. But branches which grow across or through the crown, or which rub, should also be removed.

Some arborists began expanding their list of allowable pruning cuts until the guidelines became meaningless. We recently found the following on an arborist’s web site:

“First we take care of the 4 D’s, then we’ll go into the crown and clean it up.”

That’s a clear sign the tree will be excessively pruned, and you should be looking for a new arborist.

4 d’S FROM tREE pEOPLE of los angeles, CA

This video from the original Tree People focuses on fruit trees, which tolerate frequent pruning. Mature amenity, or shade trees, require little or no pruning.¹

Our standard version of the 4 D’s for amenity trees follows after the video.

The 4 D’S from tree people of Walla Walla

Previous versions of the 4 D’s have not considered the age of the tree; the New 4 D’s recognizes the different pruning required at different stages of a tree’s growth. Also, the pruning guidelines on this page apply to deciduous amenity trees only. Conifers require little or no pruning throughout their lives.

Deciduous trees experience three stages of growth: juvenile, mature, and ancient. The Juvenile period covers approximately the first thirty years of a tree’s life. It is during this period that trees should attain their final form through careful, restrained, structural pruning. The cuts that a tree steward makes on a juvenile tree will determine the shape and character of a tree for the remainder of its life.

Mature trees do not require annual or routine maintenance (ie, pruning). A mature tree must not be thinned, limbed up, or “cleaned up”; the shaping was accomplished during the juvenile period.

Mature trees will require attention only in extraordinary circumstances. Most species, if left alone during their maturity, will live for hundreds of years, and some species have natural lifespans in the thousands of years. Mature trees require pruning ONLY in the following circumstances, if they have branches that are:

Improper care or the hardships of urban existence are responsible for the early decline during the Mature stage of a tree’s life.

This section originally published February, 2021

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