Page 1 of 84
C-27 LANDSCAPING CONTRACTOR LICENSE
EXAM*** QUESTIONS AND VERIFIED ANSWERS
| 2026/2027 UPDATE
1. A landscape contractor is preparing a bid for a commercial
project that requires extensive grading. According to OSHA
standards, what is the minimum distance that excavated soil
(spoil) must be kept from the edge of a trench?
A. 1 foot
B. 2 feet
C. 4 feet
D. 6 feet
❖ Rationale: OSHA regulations require that spoils and other
materials be kept at least 2 feet from the edge of an
excavation to prevent them from falling back into the
trench or causing a cave-in due to added weight on the
edge.
2. Which of the following is the most accurate method for
determining the uniformity of water distribution in an
irrigation zone?
A. Visual observation of spray patterns
B. Measuring the system's static pressure
,Page 2 of 84
C. Conducting a catch-can test
D. Calculating the flow rate in gallons per minute
❖ Rationale: A catch-can test involves placing identical
containers throughout the irrigation zone and measuring
the water collected after a set run time. This provides
quantifiable data on distribution uniformity (DU), which is
the industry standard for assessing system efficiency and
identifying coverage issues .
3. A client requests a landscape design that minimizes water
use. Which principle of xeriscaping is MOST critical for long-
term success?
A. Using only native plants
B. Grouping plants with similar water needs (hydrozoning)
C. Installing a high-efficiency sprinkler system
D. Applying a thick layer of gravel mulch
❖ Rationale: Hydrozoning, or grouping plants by their water
requirements, is a core principle of xeriscaping. This allows
for efficient irrigation by delivering the precise amount of
water each zone needs, preventing overwatering of
drought-tolerant plants and underwatering of thirsty ones .
4. A soil test reveals a pH of 8.5 for a site where azaleas and
rhododendrons are to be planted. To successfully establish
these plants, the contractor should FIRST:
A. Add lime to the soil
,Page 3 of 84
B. Apply elemental sulfur to lower the pH
C. Increase the frequency of irrigation
D. Select a different plant species
❖ Rationale: Azaleas and rhododendrons require acidic soil
(pH 4.5-6.0). A pH of 8.5 is highly alkaline. Elemental sulfur
is a common soil amendment used to lower pH. Lime is
used to raise pH, and increasing irrigation will not
effectively change soil pH .
5. What is the primary purpose of a backflow prevention
device in an irrigation system?
A. To increase water pressure
B. To filter sediment from the water
C. To prevent contaminated water from entering the potable
water supply
D. To regulate the flow of water to each zone
❖ Rationale: Backflow preventers are critical safety devices
that protect the public drinking water supply. They prevent
the reverse flow of water from the irrigation system—
which may contain fertilizers, pesticides, or soil-borne
bacteria—from being siphoned back into the main water
line .
6. When installing a dry-stacked stone retaining wall, what is
the primary structural principle that prevents it from failing?
A. Using mortar to bind the stones together
, Page 4 of 84
B. Installing a concrete footing below the frost line
C. The interlocking geometry and weight of the stones, with
proper batter
D. Backfilling the wall with clay soil to create a watertight seal
❖ Rationale: A dry-stacked wall relies on gravity and friction.
The wall must be built with a slight "batter" (leaning back
into the slope) and using stones that interlock well. Proper
drainage behind the wall is also critical to prevent
hydrostatic pressure build-up, but the structure itself is
held together by its weight and friction, not mortar.
7. A homeowner reports that their lawn has brown patches
and the sod can be easily rolled back like a carpet. Upon
inspection, the contractor finds white, C-shaped grubs feeding
on the roots. What is the most likely pest and the best
management strategy?
A. Japanese beetle larvae; apply a targeted insecticide in late
summer or early fall when grubs are young
B. Earthworms; reduce irrigation to dry out the soil
C. Sod webworms; apply a fungicide to the affected areas
D. Chinch bugs; dethatch the lawn to remove their habitat
❖ Rationale: The description of C-shaped grubs feeding on
roots and sod rolling back is classic for white grubs (e.g.,
Japanese beetle larvae). The most effective management is
to apply a preventative or curative insecticide when the
C-27 LANDSCAPING CONTRACTOR LICENSE
EXAM*** QUESTIONS AND VERIFIED ANSWERS
| 2026/2027 UPDATE
1. A landscape contractor is preparing a bid for a commercial
project that requires extensive grading. According to OSHA
standards, what is the minimum distance that excavated soil
(spoil) must be kept from the edge of a trench?
A. 1 foot
B. 2 feet
C. 4 feet
D. 6 feet
❖ Rationale: OSHA regulations require that spoils and other
materials be kept at least 2 feet from the edge of an
excavation to prevent them from falling back into the
trench or causing a cave-in due to added weight on the
edge.
2. Which of the following is the most accurate method for
determining the uniformity of water distribution in an
irrigation zone?
A. Visual observation of spray patterns
B. Measuring the system's static pressure
,Page 2 of 84
C. Conducting a catch-can test
D. Calculating the flow rate in gallons per minute
❖ Rationale: A catch-can test involves placing identical
containers throughout the irrigation zone and measuring
the water collected after a set run time. This provides
quantifiable data on distribution uniformity (DU), which is
the industry standard for assessing system efficiency and
identifying coverage issues .
3. A client requests a landscape design that minimizes water
use. Which principle of xeriscaping is MOST critical for long-
term success?
A. Using only native plants
B. Grouping plants with similar water needs (hydrozoning)
C. Installing a high-efficiency sprinkler system
D. Applying a thick layer of gravel mulch
❖ Rationale: Hydrozoning, or grouping plants by their water
requirements, is a core principle of xeriscaping. This allows
for efficient irrigation by delivering the precise amount of
water each zone needs, preventing overwatering of
drought-tolerant plants and underwatering of thirsty ones .
4. A soil test reveals a pH of 8.5 for a site where azaleas and
rhododendrons are to be planted. To successfully establish
these plants, the contractor should FIRST:
A. Add lime to the soil
,Page 3 of 84
B. Apply elemental sulfur to lower the pH
C. Increase the frequency of irrigation
D. Select a different plant species
❖ Rationale: Azaleas and rhododendrons require acidic soil
(pH 4.5-6.0). A pH of 8.5 is highly alkaline. Elemental sulfur
is a common soil amendment used to lower pH. Lime is
used to raise pH, and increasing irrigation will not
effectively change soil pH .
5. What is the primary purpose of a backflow prevention
device in an irrigation system?
A. To increase water pressure
B. To filter sediment from the water
C. To prevent contaminated water from entering the potable
water supply
D. To regulate the flow of water to each zone
❖ Rationale: Backflow preventers are critical safety devices
that protect the public drinking water supply. They prevent
the reverse flow of water from the irrigation system—
which may contain fertilizers, pesticides, or soil-borne
bacteria—from being siphoned back into the main water
line .
6. When installing a dry-stacked stone retaining wall, what is
the primary structural principle that prevents it from failing?
A. Using mortar to bind the stones together
, Page 4 of 84
B. Installing a concrete footing below the frost line
C. The interlocking geometry and weight of the stones, with
proper batter
D. Backfilling the wall with clay soil to create a watertight seal
❖ Rationale: A dry-stacked wall relies on gravity and friction.
The wall must be built with a slight "batter" (leaning back
into the slope) and using stones that interlock well. Proper
drainage behind the wall is also critical to prevent
hydrostatic pressure build-up, but the structure itself is
held together by its weight and friction, not mortar.
7. A homeowner reports that their lawn has brown patches
and the sod can be easily rolled back like a carpet. Upon
inspection, the contractor finds white, C-shaped grubs feeding
on the roots. What is the most likely pest and the best
management strategy?
A. Japanese beetle larvae; apply a targeted insecticide in late
summer or early fall when grubs are young
B. Earthworms; reduce irrigation to dry out the soil
C. Sod webworms; apply a fungicide to the affected areas
D. Chinch bugs; dethatch the lawn to remove their habitat
❖ Rationale: The description of C-shaped grubs feeding on
roots and sod rolling back is classic for white grubs (e.g.,
Japanese beetle larvae). The most effective management is
to apply a preventative or curative insecticide when the
