C-27 Landscaping exam questions, with answers
10 practice questions for the CSLB Landscaping trade exam, each with the answer, a plain explanation and the source it rests on.
These are not real exam questions. CSLB does not release its test questions or answer keys, and nobody else has them. We write our own questions from the C-27 outline and the codes, standards and references CSLB lists for the exam. Each answer names its source so you can check it.
The C-27 exam has 6 sections. The questions below are grouped by section, with the share of the exam each one carries. Read the question, pick an answer, then open “Show the answer”. The other questions of the free test, scored section by section, are in the free 25-question C-27 test.
Planning and Estimating · 18% of the exam
Project planning; hardscape, drainage and irrigation design; project estimating.
1. You are dividing a planting plan into valve zones for a MWELO performance-option irrigation design. One bed has shade trees growing among shrubs and groundcover. Where feasible, how does MWELO say the trees should be handled?
- Put the trees on the shrub station so the whole bed gets one run time
- Leave the trees off the system, because trees are not part of a hydrozone
- Put the trees on stations separate from the other plants
- Water the trees only with the spray heads that serve the nearest turf
Show the answer
Answer: C. MWELO §493.2.2(d)(4): where feasible, trees are placed on separate stations from hydrozones that include shrubs, groundcovers and turfgrass, so the trees can be irrigated appropriately; the mature size and extent of the root zone are considered in the design. On a shared station the trees and the smaller plants get the same run time, so one of them is watered wrongly.
2. A lawn is shaped like a trapezoid. Its two parallel edges are 30 ft and 42 ft long, and they are 20 ft apart, measured square (perpendicular) between them. What is the area of the lawn?
- 600 sq ft
- 720 sq ft
- 840 sq ft
- 1,440 sq ft
Show the answer
Answer: B. Split the shape into a 30 ft × 20 ft rectangle (600 sq ft) plus the leftover triangles, which together have a 12-ft base and a 20-ft height: 12 × 20 × 0.5 = 120 sq ft. Total 720 sq ft, the same as the average of the two parallel edges (36 ft) times 20 ft. Using only the short edge gives 600, only the long edge 840, and adding the edges without averaging gives 1,440.
Construction Preparation · 12% of the exam
Site planning; erosion control; trenching and grading.
3. The soil test for a new lawn area shows a strongly acidic soil, pH 5.2, and the lab recommends raising the pH before planting. According to Iowa State University Extension, which amendment raises the pH of an acidic soil?
- Elemental sulfur, worked into the soil before planting
- Aluminum sulfate, worked into the soil before planting
- Canadian sphagnum peat moss, worked into the soil
- Lime, worked into the soil before planting
Show the answer
Answer: D. Iowa State Extension: the pH of acidic soil is raised by adding lime, and lime and sulfur must be mixed into the top 6 to 8 inches because they are not water-soluble. Sulfur does the opposite, and aluminum sulfate and Canadian sphagnum peat moss are also materials that Iowa State describes for lowering pH, so all three would push this soil further the wrong way.
Source: Iowa State Extension, How to Change Your Soil's pH (lime raises pH; incorporate before planting)
Hardscape Installation · 21% of the exam
Flatwork; masonry; posts, fences and retaining walls; water features.
4. Your finisher has just floated a new concrete walkway at a client's front entry. According to NRMCA's finishing guidance, how is exterior flatwork such as a sidewalk, patio or driveway textured so that it is not slippery?
- By letting the bleed water dry on it with no more work
- By pulling a coarse or fine push broom across it
- By steel-troweling it to a hard, glassy surface
- By sprinkling dry cement on it and troweling that in
Show the answer
Answer: B. NRMCA CIP 14: exterior flatwork is textured after floating with a coarse or fine push broom to give a non-slip surface. A hard steel-troweled finish is slick when wet, and the same sheet says never to sprinkle water or cement on the surface to help finishing, because that causes dusting or scaling.
5. You are planning the power supply for the pump of a new backyard pond. What does Aquascape's pump guidance recommend?
- A dedicated outdoor-rated GFCI outlet close to the pump
- A splice into the low-voltage cable of the landscape lights
- A long outdoor extension cord from the nearest indoor outlet
- A two-prong adapter so the plug fits an old ungrounded outlet
Show the answer
Answer: A. Aquascape recommends a dedicated outdoor-rated GFCI outlet within close proximity to the pump. A ground-fault circuit interrupter cuts the power when current leaks to ground, which is the shock hazard around water; an extension cord adds voltage drop and exposed connections, a two-prong adapter removes the ground, and a 12-volt lighting cable cannot run a 120-volt pump.
Drainage, Irrigation, Lighting, and Plant Installation · 21% of the exam
Drainage systems and bioswales; irrigation valves and controllers; lighting controllers and transformers; plant, tree and mulch installation.
6. You are shaping a grassed swale that will carry runoff along the edge of a lawn. According to EPA's grassed swale fact sheet, how are the sides of a swale usually built?
- Relatively flat, flatter than 3:1
- Steep, about 1:1, to speed the water up
- Undercut, so the top edge overhangs
- Vertical, like a trench, to save space
Show the answer
Answer: A. EPA: swales often have a trapezoidal or parabolic cross-section with relatively flat side slopes, flatter than 3:1 (a slope ratio read as horizontal run to vertical rise, so at least 3 ft across for each 1 ft of drop). Flat sides put more of the flow in contact with the vegetated surface, which slows the water and helps filtering and infiltration; steep, vertical or undercut banks do the opposite.
Source: EPA, Grassed Swales fact sheet, Design Considerations (cross-sectional geometry)
7. A MWELO performance-option plan shows shrub beds covered with the required layer of mulch. What kind of irrigation does the ordinance require in mulched planting areas?
- Fixed spray heads laid out with head-to-head coverage
- Hand watering only, with no permanent irrigation system
- Low-pressure, low-volume irrigation such as drip
- Rotor heads on risers tall enough to throw over the mulch
Show the answer
Answer: C. MWELO §493.2.2(d)(5): in mulched planting areas, low-pressure and low-volume irrigation systems are required, to maximize water infiltration into the root zone. Spray thrown over the bed has to soak through the mulch first; drip applies the water slowly at the soil.
Maintenance and Repair · 11% of the exam
Pruning and tree removal; troubleshooting irrigation systems; repairing hardscapes.
8. While pruning a young shade tree you find two branches joined at a narrow, V-shaped angle, with a wedge of bark rolled inward between them. According to the USDA Forest Service pruning guide, what is this condition, and why does it matter?
- A branch collar; it has to stay on the tree at every cut
- Included bark; it keeps the branches from attaching strongly
- Woundwood; it shows that an old cut is closing normally
- A branch bark ridge; it shows that the union is strong
Show the answer
Answer: B. USDA Forest Service: branches with narrow, V-shaped angles of attachment often form included bark, a wedge of inward-rolled bark between them. Included bark prevents strong attachment and often leads to a crack below the union, so such branches are removed while the tree is young; branches with strong U-shaped attachments are kept.
Source: USDA Forest Service NA-FR-01-95 "How to Prune Trees", Crown Thinning (included bark)
Safety · 17% of the exam
Employee and job site safety; tree work safety.
9. In July you hire a laborer and put him on a planting crew that works in a high heat area. Under Cal/OSHA's outdoor heat illness rule (§3395), for how long must a supervisor or designee closely observe this newly assigned employee?
- For his first 14 days of employment
- For his first 3 days of employment
- For his first 7 days of employment
- For his first shift only
Show the answer
Answer: A. §3395(g)(2): an employee newly assigned to a high heat area must be closely observed by a supervisor or designee for the first 14 days of employment. The body needs time to adjust to working in heat (acclimatization), and new workers are the ones most often hurt by heat illness.
10. An excavator is lifting bundles of drain pipe and swinging them over a trench where two members of your crew are working. What does Cal/OSHA's excavation rule (§1541) say about this?
- Employees may stay under the load if it weighs less than 500 pounds
- Employees may stay under the load as long as they are wearing hard hats
- Employees may stay under the load as long as a spotter is watching it
- No employee may be under a load handled by that equipment
Show the answer
Answer: D. §1541(e): no employee shall be permitted underneath loads handled by lifting or digging equipment, and employees must stand away from vehicles being loaded or unloaded. A hard hat or a spotter does not stop a falling bundle of pipe or a dropped bucket load, and the rule has no weight exception.
Source: 8 CCR §1541(e), Cal. Code of Regulations, Title 8, §1541 Excavations, General Requirements
Where to go from here
How the license works, from experience to fees: how to get a C-27 license. Everything about the course: the C-27 exam page.
Questions from our free C-27 test, written from CSLB License Examination Study Guide, Landscaping (C-27), form 13E-27 (03-2026), for examinations scheduled on or after July 1, 2026. CSLB notes that the percentages are approximate. Reviewed 14 October 2026. Study guidance only; we are not affiliated with CSLB or PSI.