ISA Certified Arborist Exam Practice
Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. Which of the following is a primary factor in determining a tree’s site
suitability?
A. Leaf color
B. Soil texture
C. Soil drainage
D. Trunk diameter
Rationale: Soil drainage affects root oxygen availability and water
retention, making it a critical factor for tree health.
2. Which nutrient is most commonly deficient in urban trees?
A. Phosphorus
B. Nitrogen
C. Potassium
, D. Calcium
Rationale: Nitrogen deficiency is common in urban environments due
to limited organic matter and high nutrient demand.
3. What is the term for a tree that has a single main trunk?
A. Multi-stemmed
B. Monopodial
C. Coppiced
D. Dichotomous
Rationale: Monopodial growth refers to a single, dominant main
trunk with lateral branches.
4. Which pruning method encourages strong branch structure in young
trees?
A. Topping
B. Pollarding
C. Structural pruning
D. Thinning cuts
Rationale: Structural pruning helps develop a strong central leader
and well-spaced branches to prevent future defects.
5. Which of the following is a common symptom of Phytophthora root
rot?
A. Leaf curling
B. Gall formation
C. Declining crown with root discoloration
, D. Powdery leaf coating
Rationale: Phytophthora root rot typically causes root necrosis and
progressive canopy dieback.
6. What is the minimum distance recommended between newly planted
trees and underground utilities?
A. 1 foot
B. 5 feet
C. 10 feet
D. 20 feet
Rationale: A minimum of 5 feet helps prevent root interference with
underground utilities.
7. Which type of mycorrhizal association is most common in forest trees?
A. Endomycorrhizae
B. Ectomycorrhizae
C. Arbuscular
D. Orchid
Rationale: Ectomycorrhizae are common in temperate forest trees,
forming a sheath around roots to enhance nutrient uptake.
8. The primary function of phloem is:
A. Water transport
B. Transport of carbohydrates
C. Structural support
D. Gas exchange
, Rationale: Phloem translocates sugars and other organic compounds
from leaves to roots and storage tissues.
9. Which method is recommended to prevent tree girdling during
planting?
A. Mulch in contact with the trunk
B. Plant deeply to stabilize
C. Remove circling roots
D. Stake tightly for the first year
Rationale: Circling roots can strangle the trunk as the tree grows;
removing them prevents girdling.
10. What is the most common cause of mechanical injury to trees in
urban areas?
A. Ice storms
B. Fungal infection
C. Mowing and string trimming
D. Soil compaction
Rationale: Lawn maintenance equipment frequently damages bark,
creating entry points for pests and pathogens.
11. Which of the following species is most susceptible to Dutch elm
disease?
A. Red maple
B. White oak
C. American elm
Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. Which of the following is a primary factor in determining a tree’s site
suitability?
A. Leaf color
B. Soil texture
C. Soil drainage
D. Trunk diameter
Rationale: Soil drainage affects root oxygen availability and water
retention, making it a critical factor for tree health.
2. Which nutrient is most commonly deficient in urban trees?
A. Phosphorus
B. Nitrogen
C. Potassium
, D. Calcium
Rationale: Nitrogen deficiency is common in urban environments due
to limited organic matter and high nutrient demand.
3. What is the term for a tree that has a single main trunk?
A. Multi-stemmed
B. Monopodial
C. Coppiced
D. Dichotomous
Rationale: Monopodial growth refers to a single, dominant main
trunk with lateral branches.
4. Which pruning method encourages strong branch structure in young
trees?
A. Topping
B. Pollarding
C. Structural pruning
D. Thinning cuts
Rationale: Structural pruning helps develop a strong central leader
and well-spaced branches to prevent future defects.
5. Which of the following is a common symptom of Phytophthora root
rot?
A. Leaf curling
B. Gall formation
C. Declining crown with root discoloration
, D. Powdery leaf coating
Rationale: Phytophthora root rot typically causes root necrosis and
progressive canopy dieback.
6. What is the minimum distance recommended between newly planted
trees and underground utilities?
A. 1 foot
B. 5 feet
C. 10 feet
D. 20 feet
Rationale: A minimum of 5 feet helps prevent root interference with
underground utilities.
7. Which type of mycorrhizal association is most common in forest trees?
A. Endomycorrhizae
B. Ectomycorrhizae
C. Arbuscular
D. Orchid
Rationale: Ectomycorrhizae are common in temperate forest trees,
forming a sheath around roots to enhance nutrient uptake.
8. The primary function of phloem is:
A. Water transport
B. Transport of carbohydrates
C. Structural support
D. Gas exchange
, Rationale: Phloem translocates sugars and other organic compounds
from leaves to roots and storage tissues.
9. Which method is recommended to prevent tree girdling during
planting?
A. Mulch in contact with the trunk
B. Plant deeply to stabilize
C. Remove circling roots
D. Stake tightly for the first year
Rationale: Circling roots can strangle the trunk as the tree grows;
removing them prevents girdling.
10. What is the most common cause of mechanical injury to trees in
urban areas?
A. Ice storms
B. Fungal infection
C. Mowing and string trimming
D. Soil compaction
Rationale: Lawn maintenance equipment frequently damages bark,
creating entry points for pests and pathogens.
11. Which of the following species is most susceptible to Dutch elm
disease?
A. Red maple
B. White oak
C. American elm
