CLARB Planting Design and Ecology 2 — Questions and Answers
Question 1: A designer specifies Quercus palustris (pin oak) for a parking lot island. What soil pH concern should be noted?
- Pin oak is susceptible to iron chlorosis in high pH (alkaline) soils common near concrete (Correct answer)
- Pin oak requires highly acidic soils below pH 4.0
- Pin oak thrives in saline soils typical of coastal areas
- Pin oak requires soil pH above 8.0 for optimal growth
Correct answer: Pin oak is susceptible to iron chlorosis in high pH (alkaline) soils common near concrete
Pin oak develops interveinal chlorosis when planted in alkaline soils (pH above 7.0) because iron becomes unavailable, making it a poor choice near concrete curbs.
Question 2: What is allelopathy in the context of planting design?
- The chemical inhibition of growth in neighboring plants by compounds released from certain species (Correct answer)
- The symbiotic relationship between plants and mycorrhizal fungi
- The attraction of pollinators through floral scent compounds
- The process of seed dispersal by wind
Correct answer: The chemical inhibition of growth in neighboring plants by compounds released from certain species
Allelopathy occurs when a plant releases biochemicals that inhibit germination or growth of other plants nearby, such as black walnut (Juglans nigra) producing juglone.
Question 3: Which planting design principle ensures that plants provide multi-season interest across spring, summer, fall, and winter?
- Sequential or year-round interest through selection of plants with overlapping seasonal features (Correct answer)
- Monoculture planting for simplicity
- Using only evergreen species
- Planting only spring-blooming species
Correct answer: Sequential or year-round interest through selection of plants with overlapping seasonal features
Selecting plants with varied bloom times, fall color, fruit, bark texture, and winter structure ensures the landscape remains visually engaging throughout the year.
Question 4: What minimum clear trunk height is typically specified for street trees to provide clearance for pedestrians?
- 8 feet minimum clearance over pedestrian paths (Correct answer)
- 3 feet minimum clearance
- 12 feet minimum clearance
- 18 inches minimum clearance
Correct answer: 8 feet minimum clearance over pedestrian paths
Street trees are typically pruned or trained to maintain at least 8 feet of clear trunk height over sidewalks to ensure safe pedestrian passage.
Question 5: A planting plan calls for 'native species only.' Which of the following best describes a native plant in the US context?
- A species that occurred naturally in a region prior to European colonization (Correct answer)
- Any plant grown in a US nursery
- A plant that has naturalized and grows wild without cultivation
- Any non-invasive ornamental species
Correct answer: A species that occurred naturally in a region prior to European colonization
Native plants are those that evolved and existed in a specific region before European settlement, forming ecological relationships with local wildlife and soil organisms.
Question 6: When specifying trees near underground utilities, what is the most important consideration to avoid long-term conflicts?
- Select species with non-aggressive root systems and appropriate mature canopy size for the available space (Correct answer)
- Plant trees as close as possible to concentrate root growth
- Use only deciduous trees near utilities
- Avoid all tree planting within 50 feet of any utility
Correct answer: Select species with non-aggressive root systems and appropriate mature canopy size for the available space
Choosing trees with non-invasive roots and a mature size proportionate to the planting area prevents infrastructure damage and costly removals over time.
CLARB Planting Design and Ecology 2
A designer specifies Quercus palustris (pin oak) for a parking lot island.
What soil pH concern should be noted?