ISA Tree Pruning Practices Questions and Answers 1 — Questions and Answers
Question 1: An arborist is tasked with reducing the length of a major limb on a mature maple tree to provide clearance for a nearby structure. To maintain structural integrity and promote proper wound closure, which type of pruning cut is most appropriate for this task?
- A heading cut
- A flush cut
- A reduction cut (drop-crotching) (Correct answer)
- A removal cut (collar cut)
Correct answer: A reduction cut (drop-crotching)
A reduction cut, also known as drop-crotching, is the correct technique for reducing the length of a large branch. This cut shortens a limb back to a lateral branch that is large enough (at least one-third the diameter of the removed portion) to assume the terminal role, which helps maintain a natural form and promotes compartmentalization. Heading cuts on large branches are a form of topping that leads to decay and weakly attached sprouts. A flush cut removes the branch collar, damaging trunk tissue and inhibiting wound closure. A removal cut is used to take off an entire branch at its point of origin, not to shorten it.
Question 2: A client hires an arborist to prune a dense, overgrown crabapple tree. The client's main objective is to allow more light and air to penetrate the canopy. According to ANSI A300 standards, which pruning type should the arborist specify in the work order?
- Crown raising
- Crown cleaning
- Crown restoration
- Crown thinning (Correct answer)
Correct answer: Crown thinning
Crown thinning is the selective removal of branches to reduce the density of the canopy. This practice increases light penetration and air movement, which addresses the client's objectives. Crown cleaning removes dead, diseased, or broken branches. Crown raising removes lower branches to provide clearance. Crown restoration is used to improve the structure of a tree that has been damaged or poorly pruned previously.
Question 3: While training a young oak tree, an arborist identifies two codominant stems of roughly equal size that are forming a weak, V-shaped union with included bark. To develop a strong central leader and reduce the risk of future failure, the most appropriate long-term strategy is:
- Install a cable between the two stems for support.
- Remove both stems to allow a new leader to develop.
- Subordinate one of the stems by reducing its length. (Correct answer)
- Head back both stems equally to encourage lower branching.
Correct answer: Subordinate one of the stems by reducing its length.
Subordination is the best practice for correcting codominant stems in a young tree. By reducing the length of one of the competing stems (using a reduction cut), its growth is slowed, allowing the other stem to establish itself as the dominant central leader. This improves the tree's structure and reduces the likelihood of the weak union failing later in the tree's life. Cabling is typically reserved for mature trees where removal or subordination is not feasible. Removing or heading both stems would be detrimental to the tree's structure.
Question 4: Which of the following is a common, negative consequence of "lion's tailing," a pruning practice where an excessive number of interior and lateral branches are removed from limbs?
- Increased light interception by the inner canopy
- Reduced wind resistance and sail effect
- Increased risk of sunscald on branches and branch failure (Correct answer)
- Improved taper and structural stability of the limbs
Correct answer: Increased risk of sunscald on branches and branch failure
Lion's tailing is an improper pruning practice that displaces foliage to the ends of the branches. This redistribution of weight increases the likelihood of branch failure, especially during wind or ice events. It also exposes the tops of branches to direct sunlight, which can cause sunscald. This practice reduces, rather than improves, structural stability and can trigger stress responses like epicormic sprouting.
Question 5: When removing a large, heavy limb from a tree, the three-cut method is recommended primarily to:
- Ensure the final cut is perfectly flush with the trunk.
- Prevent the weight of the branch from tearing the bark down the trunk. (Correct answer)
- Speed up the overall pruning process.
- Sterilize the wound as the final cut is made.
Correct answer: Prevent the weight of the branch from tearing the bark down the trunk.
The three-cut method is a safety and tree health technique used for removing large branches. The first two cuts (an undercut followed by a top cut farther out on the limb) remove the bulk of the branch's weight. This prevents the branch from falling and ripping a long strip of bark from the trunk as the final cut is made. The third and final cut is then made just outside the branch collar to remove the remaining stub, allowing for proper wound closure.
Question 6: According to ANSI A300 pruning standards, what is the general recommendation for the maximum amount of live foliage that should be removed from a mature tree in a single year?
- 10 percent
- 50 percent
- As much as needed to achieve the objective
- 25 percent (Correct answer)
Correct answer: 25 percent
The ANSI A300 standards, which guide best practices in arboriculture, specify that no more than 25 percent of a tree's foliage should be removed in a single year. Removing more than this can put the tree under severe stress, reduce its ability to photosynthesize, and make it more susceptible to pests and diseases. For mature trees, the percentage is often even less.
