Tree Defects

A tree defect is any feature, condition, or deformity of a tree that indicates weak structure or instability that could contribute to tree failure. Some common types of tree defects to look out for include:

Codominant Stems

Two or more stems that grow upward from a single point of origin and compete with one another.

  • Common with decurrent growth habits
  • Occurs in excurrent trees only after the leader is killed and multiple leaders compete for dominance

Included Bark

Bark is incorporated in the joint between two limbs, creating a weak attachment.

  • Occurs in branch unions with a high attachment angle (i.e. v-shaped unions)
  • Common in many columnar/fastigiate growing deciduous trees

Dead, Diseased, or Broken Branches

  • Woundwood cannot grow over stubs or dead branches to seal off decay
  • Symptoms/signs of disease: e.g. oozing through the bark, sunken areas in the bark, and bark with abnormal patterns or colours, stunted new growth, discolouration of the foliage


  • Longitudinal cracks result from interior decay, bark rips/tears, or torsion from wind load
  • Transverse cracks result from buckled wood, often caused by unnatural loading on branches, such as lion's tailing
  • Seams: bark edges meet at a crack or wound
  • Ribs: bulges, indicating interior cracks

Cavity and Hollows

Sunken or open areas wherein a tree has suffered injury followed by decay. Further indications include: fungal fruiting structures, insect or animal nests.


A lean of more than 40% from vertical presents a risk of tree failure.


Change in diameter over the length of trunks, branches and roots.

Epicormic Branches

Water sprouts in canopy or suckers from root system. Often grow in response to major damage or excessive pruning.


  • Girdling roots compress the trunk, leading to poor trunk taper, and restrict vascular flow
  • Kinked roots provide poor structural support; the kink is a site of potential root failure
  • Circling roots occurs when roots encounter obstructions/limitations such as a small tree well or being grown too long in a nursery pot; these cannot provide adequate structural support and are limited in accessing nutrients and water
  • Healthy soil texture and depth, drainage, water availability, makes for healthy roots

Content source: Wikipedia

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