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Pruning

General

  • Removing plant parts
  • Must have a purpose
  • Essential in most planted trees, especially in early stages

Overview

  • Plant response to pruning

    • hormonal controls
    • predicting response

  • structural pruning of young trees

Why prune? Just a few examples

  • Improve structure, increase strength
  • Reduce or eliminate hazards
  • promote flowering

Plant hormones control plant response

  • Auxins (produced in SAM)
  • cytokinins (produced in roots)
  • Abscisic acid (regulates stomatal closure)
  • Ethelyene (Stress Hormone, ripening)
  • Giberellins (Plant development)

Pruning mainly focuses on cytokinins and ethelyne

Why prune mature trees?

  • Risks reduction
  • Clearance
  • Visibility
  • Utility line conflicts
  • Specialty applications (pollarding, pleaching, espalier)

Managing Pruning of mature trees

  • Many cities contract out pruning work
  • Specifications
  • Standards
  • Contracts

Three Pruning Methods/Cuts

  • Heading cuts involve trimming a branch back to a bud. This removes the shoot apical meristem and subsequently the auxin hormone signals that suppress lateral growth. So basically, heading stimulates lateral growth by removing its barriers. Heading cuts are most effective on one-two year old branches to either remove a competing leader or create hedges. Pollarding is a type of heading where branches are cut back annually to the same spot on the tree, re-invigorating lateral growth every year.
  • Thinning cuts are the most frequently used cuts in tree pruning. It involves trimming a branch to another/parent limb, giving that latter branch the terminal role. It is important that the to-be-terminal branch must be 1/3 of the diameter of the to-be-removed branch. It is also crucial to not damage the root collar when making thinning cuts.
  • Bending is technically not a cut. However, it is still a crucial part of redirecting plant/branch growth. It involves tying or stabilizing a flexible branch or shoot horizontally or vertically, altering the auxin gradient of the branch and forcing the branch to produce more ethylene, which not only reduces vegetative growth but also fuels flower & fruit production. Bending is a topic of interest for urban foresters when it comes to creating food forests. # How to Prune Right: The 3-Cut Method Belive it or not, there is a right and wrong way to prune a branch. The right way is called the 3-Cut Method, and the basic idea is shown below: [3-cut.png]

Summary

  • If you can't clearly explain to someone else why a tree should be pruned or why a particular plant part should be removed, you should not be pruning
  • You need to know your species and your objective before any pruning decisions can be made
  • Prune is a balancing act, there is an art to getting it right
  • Good pruning can extend the useful service life of individual trees in your urban forest
  • Pruning standards and clear specications are essential for achieving quality work
  • There are many specialty types of pruning that are practiced by niche horticultural business and professionals