Certified Arborist Test Tree Pruning Principles 1

Question 1

According to ISA Best Management Practices, what is the maximum percentage of live crown generally recommended to remove during a single pruning session?

Accepted Answer

25%

Answer

Removing more than 25% of a tree's live crown in one session can stress the tree by reducing its photosynthetic capacity below the level needed to sustain roots and defend against pests and pathogens. Repeated conservative pruning over multiple seasons is safer than aggressive one-time removal.

Question 2

What is 'lion's-tailing' and why is it considered poor arboricultural practice?

Accepted Answer

Removing interior lateral branches so foliage is concentrated only at branch ends

Answer

Lion's-tailing strips interior foliage and shifts weight to the ends of long lever-arm branches, increasing the risk of failure. It also removes the interior sprouts that shade the branch wood and help distribute wind load throughout the canopy, and frequently triggers heavy epicormic sprouting.

Question 3

A reduction cut is valid only when the retained lateral branch meets what minimum size requirement relative to the removed portion?

Accepted Answer

At least one-third the diameter of the removed branch

Answer

A lateral that is at least one-third the diameter of the branch being removed is large enough to take over the apical role, maintain adequate sap flow, and produce a suitably sized wound that can close efficiently. A smaller lateral cannot assume dominance and the result functionally resembles a stub.

Question 4

What does current research indicate about the use of wound dressings (pruning paint or sealants) on fresh pruning cuts?

Accepted Answer

They generally provide no measurable benefit to wound closure and may inhibit compartmentalization

Answer

Decades of research, including work by Dr. Alex Shigo, demonstrated that trees compartmentalize wounds through internal chemical and anatomical barriers — wound dressings do not enhance this process. Some sealants can actually trap moisture and pathogens beneath the surface, potentially making decay worse.

Question 5

What distinguishes a 'heading cut' from a 'thinning cut'?

Accepted Answer

A thinning cut removes a branch at its point of attachment; a heading cut removes a branch at a point other than its attachment, leaving a stub or cutting to a very small lateral

Answer

Thinning cuts remove branches entirely at their origin, maintaining the natural branching architecture and producing little regrowth. Heading cuts sever branches at arbitrary points between nodes or to undersized laterals, destroying apical dominance and triggering clusters of vigorous, weakly attached epicormic shoots at the wound site.

Certified Arborist Test Practice Test

Certified Arborist Test Practice Test

Certified Arborist Test Tree Pruning Principles 1