CLA CLA Plant Materials & Horticulture 2 — Questions and Answers
Question 1: What is the primary purpose of specifying native plants in a US landscape design?
- Lower purchase cost at nursery
- Reduce irrigation need and support local wildlife (Correct answer)
- Ensure faster growth than non-natives
- Comply with HOA color requirements
Correct answer: Reduce irrigation need and support local wildlife
Native plants are adapted to local climate and soil, requiring less supplemental water and providing habitat for native insects and wildlife.
Question 2: A landscape architect specifies Phragmites australis for a wetland restoration. Why might this be a problem?
- It is toxic to wildlife
- It is an invasive species that outcompetes native wetland plants (Correct answer)
- It requires saltwater to survive
- It cannot tolerate saturated soils
Correct answer: It is an invasive species that outcompetes native wetland plants
Common reed (Phragmites australis) is an aggressive invasive in US wetlands that forms dense monocultures and reduces biodiversity.
Question 3: Which fertilizer designation indicates the percentage of nitrogen, phosphorus (Pâ‚‚Oâ‚…), and potassium (Kâ‚‚O) respectively?
- N-K-P
- P-N-K
- N-P-K (Correct answer)
- K-P-N
Correct answer: N-P-K
The standard fertilizer grade reads N-P-K (nitrogen–phosphorus–potassium), always in that order on the bag label.
Question 4: What is the recommended planting depth for most trees to avoid crown rot?
- Root flare 2–4 inches below grade
- Root flare at or slightly above grade (Correct answer)
- Root flare 6 inches below grade
- Root flare buried under 4 inches of mulch
Correct answer: Root flare at or slightly above grade
Trees should be planted so the root flare is at or just above finished grade to prevent stem and root rot from excess soil moisture.
Question 5: Which of the following grass species is a cool-season turf commonly seeded in the upper Midwest and Northeast US?
- St. Augustinegrass
- Zoysiagrass
- Kentucky bluegrass (Correct answer)
- Bahiagrass
Correct answer: Kentucky bluegrass
Kentucky bluegrass (Poa pratensis) is a cool-season turfgrass that thrives in the northern US with cold winters and mild summers.
Question 6: What does 'dioecious' mean when used to describe a plant species?
- Having both male and female flowers on the same plant
- Having male and female flowers on separate plants (Correct answer)
- Producing flowers twice per year
- Requiring two pollinators to set fruit
Correct answer: Having male and female flowers on separate plants
Dioecious species like hollies have male and female reproductive structures on separate individual plants, requiring both sexes for fruiting.
CLA CLA Plant Materials & Horticulture 2
What is the primary purpose of specifying native plants in a US landscape design?