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ASLA 2014 Annual Meeting and EXPO
Prairie Green Roofs: High Plains, Great Plains, and Beyond
Presenters Dr. Richard K. Sutton, FASLA, UN-Lincoln Peter MacDonagh, FASLA, Kestrel Design
Andy Creath, Green Roofs of Colorado
ASLA 2014 Annual Meeting and EXPO
Prairie & Green Roof: Similarities & Differences
Great Plains vegetation is largely defined by water available after losses due to evapo-transpiration
Green Roof vegetation is largely defined by water available after losses due to evapo-transpiration
ASLA 2014 Annual Meeting and EXPO
Learning Objectives 1. Learning Objective #1 Examine key aspects of prairie plant
establishment and relate it to green roofs.
2. Learning Objective #2 Understand the links between media and plant establishment, growth, and diversity.
3. Learning Objective #3 Distinguish the advantages and disadvantages of diverse prairie plantings and sedum mono-generic cultures.
4. Learning Objective #4 Describe the key elements of green roof maintenance.
ASLA 2014 Annual Meeting and EXPO
Prairie & Green Roof: Similarities & Differences
• Prairie Biomes – Tall-grass (East) – Mixed-grass – Short-grass (West)
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ASLA 2014 Annual Meeting and EXPO
Prairie & Green Roof: Similarities & Differences
These also stress green roof plantings: 1. Negative Water Balance 2. High Winds 3. High Insolation 4. High Summer Temperatures 5. Low Winter Temperatures 6. Diurnal & Seasonal Temperature Fluxes 7. Long & Short-term Drought Oscillations
ASLA 2014 Annual Meeting and EXPO
Prairie & Green Roof: Similarities & Differences
The main difference between prairie and green roof environments lies in the depth and composition of the rhizosphere.
No deep moisture is available in shallow green roof substrates.
Water holding clay fraction eliminated
Green roofs in drought need to be irrigated, just not heavily so.
ASLA 2014 Annual Meeting and EXPO
Sedum vs. Diverse Native Prairie Plantings
Sedum Green Roof (Image Kestrel Design Group)
Prairie Green Roof (Image Kestrel Design Group)
ASLA 2014 Annual Meeting and EXPO
• Glades with shallow soil • Sand prairies • Shortgrass prairies
Kimball Co., NE Thomas Co., NE Lancaster Co., Ne Shortgrass Prairie Sandhills Blowout Sandstone Prairie
Regional Templates
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ASLA 2014 Annual Meeting and EXPO
Regional Influences on Species Selection
Bluff Bedrock Prairie Southern Minnesota
ASLA 2014 Annual Meeting and EXPO
Every state or region has its own set of potenDal templates
ASLA 2014 Annual Meeting and EXPO
Examples of prairie green roof
Municipal Building Commission, Minneapolis, Minnesota (Images © Kestrel Design Group)
ASLA 2014 Annual Meeting and EXPO
M C L
P E E C M C L
M C L
Schizachyrium scoparium little bluestem
Frequency Abundance 100 19
East Central Minnesota Bedrock Bluff Prairies
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ASLA 2014 Annual Meeting and EXPO
Green Roof Experiments, Trials and Observations in Nebraska
• Substrate depth and quality • Mychorrhizae, biomass, and fertility • Planting propagule choice and
establishment time • Seeding, recruitment, and cover • Native grass seeding to reduce costs
ASLA 2014 Annual Meeting and EXPO
Materials and Methods
• Pioneers Park Nature Center: – Native grasses & forbs planted in twelve, 1.83 m by
1.83 m (6’ X 6’) plots in an 3.1cm X 3.1cm (8” by 8”) grid of 64, 72 cells dibble boarded into the substrate
ASLA 2014 Annual Meeting and EXPO
Results
Least Squares Means for Treatment Comparisons (Significant at P<0.05)
Effect trtmt trtmt Std. Est. Error DF t-Value P>tControl v Inoc 1 2 -0.1167 0.086 8 -1.36 0.2111Control v Gel 1 3 -0.3444 0.086 8 -4.01 0.0039Control v Inoc*Gel 1 4 -0.5556 0.086 8 -6.48 0.0002Inoc v Gel 2 3 -0.2278 0.086 8 -2.65 0.0291Inoc v Inoc*Gel 2 4 -0.4389 0.086 8 -5.12 0.0009Gel v Inoc*Gel 3 4 -0.2111 0.086 8 -2.46 0.0393
ASLA 2014 Annual Meeting and EXPO
• Obvious visual differences in robustness and color between control and interaction Control
Inoc*Gel Interaction
Discussion
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ASLA 2014 Annual Meeting and EXPO
Seeding, Recruitment, and Cover
• Arbor Day Foundation Ultra-Extensive G. R.: – 37.2 m2 (400 ft2) with 5 cm (2 inches) of Carlisle
lightweight extensive over a moisture retention pad
20’ X 20’ Plot Area in sea of Sedum spp.
ASLA 2014 Annual Meeting and EXPO
Results
ASLA 2014 Annual Meeting and EXPO
Propagule Choice, Size & Timing
• Sandhills Publishing G. R. • 185.8 m2 (2000 ft2) with Semi-intensive 15.8 cm (6-in) of
custom substrate blend; hand irrigated as needed
Native Plant Trial Garden
Native Grass Seeding Plots Trial Garden
ASLA 2014 Annual Meeting and EXPO
Objectives
• Seeding density study for 5 native grasses
• Study time to
cover: Four months from seed!!
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ASLA 2014 Annual Meeting and EXPO
Results
ASLA 2014 Annual Meeting and EXPO
Native seeding to Reduce Costs
• Larson Building-Parkhouse Apartments G. R. • 557 m2 (6000 ft2) variable depth 10-15.8 cm (4-6-in) of
Midwest Trading Extensive substrate; irrigated as needed
ASLA 2014 Annual Meeting and EXPO
Objectives
• Seeding but not by hand
• Compare cost and coverage of seeding to Sedum
ASLA 2014 Annual Meeting and EXPO
Maintenance to the Design Intent • Necessity • Installation: Delivery to planting • Establishment: Coverage time • After Establishment
– Weeding, clean-up, and drainage – Annual fertility testing and application – Irrigation
• Documentation
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ASLA 2014 Annual Meeting and EXPO
Maintenance to the Design Intent • Necessity • Designing for Maintenance • Installation: Delivery to
planting • Establishment: Coverage
time • Post-Establishment • Documentation
ASLA 2014 Annual Meeting and EXPO
Necessity • There is no such thing as a maintenance-
free roof • Ensures that the design intent is fulfilled
and plants are healthy • Saves long-term costs in repairs and re-
roofings
ASLA 2014 Annual Meeting and EXPO
Necessity • To comply with manufacturer warranties • To maintain aesthetic appeal of roof
• To help comply with voluntary standards, local regulations/incentives, building codes, and insurance requirements
ASLA 2014 Annual Meeting and EXPO
Challenges
• No maintenance plan • Lack of budget • Belief that a green roof is maintenance-free • Designed without regard to maintenance • Improperly trained maintenance staff
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ASLA 2014 Annual Meeting and EXPO
Designing for Maintenance • Safety • Roof Access • Water
Access • Plant
Selection
ASLA 2014 Annual Meeting and EXPO
Designing for Maintenance
• Maintenance requirements at each stage
• All parties involved consider impact on maintenance
• Identify owner expectations early and design to it
• The type and design intent play a major role in maintenance requirements and cost
ASLA 2014 Annual Meeting and EXPO
Installation: Delivery to planting • Ensure plant
health at arrival
• Verify water access if necessary
• Stockpile in shady area until planting
ASLA 2014 Annual Meeting and EXPO
Establishment • Visit at higher
frequencies • Ensure healthy plant
development • Verify proper drain
function • Check and adjust
irrigation • Weed, prune, and
remove debris • Check for disease
and pests
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ASLA 2014 Annual Meeting and EXPO
Post-Establishment • Visit less frequently
• Ensure healthy plants • Test for annual fertility and
apply amendments if necessary
• Verify proper drain function • Check and adjust irrigation • Weed, prune, and remove
debris • Check for disease and pests
ASLA 2014 Annual Meeting and EXPO
Documentation Site visitation documentation should include the following information:
• Date and time of visit • Maintenance performed • Overall health of green roof • Time spent on roof • Testing that was performed • Amendments used/applied • Weather conditions (current and recent) • Photographic documentation
ASLA 2014 Annual Meeting and EXPO
Summary
• Native prairie plantings can make it on extensive green roofs (Peter)
• Flammability issue (Richard) • Reduced costs (Richard) • Establishment and plant selection is
critical (Andy) • Minimal yet informed maintenance (Andy)