Green Roofs and Permaculture

Growing food on rooftops is popular in many urban areas.  New York may be leading the way, especially with projects like the Eagle Street Rooftop Farm.

We are working on a Jacksonville, Florida green roof with a significant rooftop permaculture component this spring.

Vegetables are already seeded and many sprouting.  The Dinosaur Kale is about sixteen inches tall and the rocket arugula is growing well also.

We chose the roof area with the most morning sun and afternoon shade for the garden area as roof temperatures climb rapidly during the afternoon.  Though many vegetables, such as the Brassicaceae are considered C4 photosynthesis processing plants and drought tolerant, morning sun and afternoon shade is best.

Here back in the green roof plant nursery we have recently adopted farm fowl on our urban one acre lot.  With several chickens, ducks, geese and a turkey we've had to build enclosures to keep the neighborhood cats, raccoons and hawks from eating our birds.

This weekend we successfully constructed the $50.00 turkey enclosure.  At 200 SF the price per square foot calculates to be approximately twenty five cents per SF - not bad!

Green Roof Turkey House

The turkey castle is roofed with lemongrass, spinach, borage, onions, parsley, cucumbers, cantaloupe and cow peas.

The enclosure is made with simple farm posts, bent electrical conduit and wildlife - bird netting.

The soil media for the green roof is a very lightweight mix of perlite, vermiculite, sand and compost (compost about 50%).  We'll keep the roof fertilized with turkey pellets.

Green Roofs and Permaculture

And as our turkey appears to be a good flyer - I suspect he will be roosting often with the veggies.

Integrating vegetables, fruit and other items such as honey not only provides food for people but also habitat for wildlife.  Increasing the plants insects need increases biodiversity.  Pollinators are an important component of urban core gardening.

Rooftop permaculture - the new frontier for green roofs!

Green Roof & Rooftop permaculture - Economic Opportunity for the Urban Core

One of the components of the new Breaking Ground Contracting green roof will be a working permaculture garden.

Today we will be planting 10,000 yellow onions and garlic cloves for the project.  The cloves and onion sets are already sprouting so within a week the plants should be nice and green for end of month installation.

Garlic cloves for the BGC Green Roof Permaculture Garden & Green Roof

I was peeling apart heads of garlic until midnight last night.  Good time for green roof planting now due to the new moon.

Learning about Native Plants for Living Walls & Green Roofs

Native plants play an important role in supporting worldwide biodiversity heritage.

For a great blog post on just how important native plants are for supporting biodiversity, read the post here at Wildlife Garden.

One of the many ways to learn about native plants is to 'look up'.  This week I spent several hours walking in the moat of the old Spanish Fort in St. Augustine.  In my opinion the National Park Service has it backwards - they charge for going inside the fort but allow you to walk for free in the moat and around the grounds.  The moat is where you can see many, many native and other plants species growing in the coquina walls!

Castillo de San Marco, St. Augustine

As you can see in the above photo, most plants grow underneath the downspouts on the walls.  Though the downspouts provide water primarily when it rains, they also collect dew and fog from surrounding areas and funnel the water to the plants.

Interestingly, learning about green roof and living walls plants from the fort offers insight into those plants that not only do well under the hot Florida sun and with no additional irrigation, but also the plants shed light on soil media composition.

Coquina shell and the limestome mortar have a quite high pH level.  High pH is usually one of the toughest issues to work with on green roofs and living walls.

Samolus valerandi

Pteris vittata & 2 Cuban anoles

Wildlife seeks out plants, especially those providing resource benefit such as food or nectar or shelter.  Native plants are best suited at providing the most optimum level of ecological benefit to those wildlife endemic to an area.

In otherwords, planting native plants on green roofs and living walls encourages and supports native populations of insects, birds, reptiles, amphibians and other wildlife.

Many popular landscape plants used on green roofs may not offer the same level of resource benefit.

Learning about your local native plants broadens design capabilities for both green roofs and living walls.

Limestone & Coquina Walls are Harsh Ecosystems

Green Roof, Southern France from Natural Materials & Native Plant Species

Very excited to share a series of photographs of a green roof in Southern France constructed primarily using natural materials rather than massive amounts of plastic trays and parts.

The basic design was fashioned from the LivingRoofs.org design guide - a great resource for anyone interested in constructing a green roof.  The LivingRoofs.org is, in my opinion, one of the very best resources for green roof design.  Rather than focusing on commercial advertising the LivingRoofs.org site focuses on making available important design data and examples of green roofs from around the world.

The photos here depict in chronological order the basic system approach.

Thorough research into native plants was conducted, inventorying local native plant species according to bloom time, life cycle, biodiversity value, maintenance requirements, water issues and drought tolerant qualities and more.

Interestingly, native reed, Arundo species was used for drainage along with broken and crushed tile, stone, sand and compost.

The reed used is a endemic plant, one used locally for roofs.  Reed roofs have been historically popular in the Mediterranean area and can last as long if not longer than asphalt shingles.  For an interesting review of reeds used for roofing material check out the many websites offering reed roofing products.

This project is particularly significant in the evolution of world-wide green roof technology as it is a strong statement concerning sustainability and biodiversity.

In many aspects our green roof industry has become stale and stagnant.  Most if not all systems today are plastics based, have extremely high carbon footprints with use of petro-kiln expanded inorganics for soil media, use monocultures of one or two plant Genus - most of which are exotic plants not even native to the area.

All this is great for the bank.  But not so good for site ecology.

Today, in my opinion many green roof systems are 'greenwashed' with true sustainability value.

Some say green roofs constructed around monocultures of exotic plants that require regular irrigation and fertilization may be better than asphalt roofs.  However, in my opinion, the forced use of exotic landscape plants on a roof filled with plastic trays is no different than GMO practices - forcing an unnatural product into our environments.

So this green roof in Southern France may have now set the standard for all future truly sustainable green roofs.

Native plants with ethnobotanical and biodiversity value cover the native soil and drainage materials.  The woven geo-synthetic fabric is the only material not found locally in nature - and this could possibly be replaced with hemp fabric or cotton burlap.

When I look at this roof I see the beauty of native and natural materials.  I do not see in black plastics and overused plants.

I can tell you the industry will immediately point to long term life cycling comparisons.  They will argue expanded shale lasts forever whereas green roofs using natural materials will decompose over time.  Big corporate green roof industry will argue that the mats of one or two plant Genus are extremely low maintenance and much better suited for the general population than wildflower populations that may evolve and change with the seasons.

But this roof, designed with ingenuity and a heart for long-term biodiversity and sustainability is greater in significance, in my mind, than the largest turf or sedum roof built in the last decade.

The methods, materials and plant design here now becomes a standard of sustainability for green roofs.

Certainly improvements and adjustments will be developed and implemented.  Yet the statement of a true 'green' roof leaves a lasting impression in my mind.

Enjoy the photos.  For more information contact the designer and builder on twitter - http://twitter.com/toitsverts

Geosynthetic liner

Arundo Reed

Drainage layer - Reed

Crushed tile & reed

Native Plants for Biodiversity & Ethnobotany

Using Native Plants for Green Roof Species

Green Roof Native Plants

Benefits of Green Roofs - Fighting Cancer and Other Diseases

Green roofs and living walls can help clean the air and allow us to breath easier.


Many geographic locations acros the globe have air contaminated with Volatile Organice Compounds also known as VOCs.


Volatile Organic Compounds (VOCs) are chemicals created by industrial pollution and automobile engines among other processes.  VOCs are the primary cause of Urban Smog.  


They are also responsible for the formation of cancers, respiratory problems and other serious health issues.

According to the US EPA, the Health Effects of VOCs include:

Eye, nose, and throat irritation; headaches, loss of coordination, nausea; damage to liver, kidney, and central nervous system. Some organics can cause cancer in animals; some are suspected or known to cause cancer in humans. Key signs or symptoms associated with exposure to VOCs include conjunctival irritation, nose and throat discomfort, headache, allergic skin reaction, dyspnea, declines in serum cholinesterase levels, nausea, emesis, epistaxis, fatigue, dizziness.

The ability of organic chemicals to cause health effects varies greatly from those that are highly toxic, to those with no known health effect. As with other pollutants, the extent and nature of the health effect will depend on many factors including level of exposure and length of time exposed. Eye and respiratory tract irritation, headaches, dizziness, visual disorders, and memory impairment are among the immediate symptoms that some people have experienced soon after exposure to some organics. At present, not much is known about what health effects occur from the levels of organics usually found in homes. Many organic compounds are known to cause cancer in animals; some are suspected of causing, or are known to cause, cancer in humans.

For more health information on VOCs from the EPA click here. 

According to a new study - one confirming what we already know - plants -  - clean these harmful VOCs out of the air.   Read about the study in a National Science Foundation Article here.

This study makes it clear that it is especially important to have as many plants inside your building or home as the levels of VOCs inside a structure can be up to ten times the ambient levels outside.


Plants act as filters for air and rainfall, actually removing and utilizing harmful nitrogen.  They also remove carbon from the atmosphere by using CO2 to produce much needed energy compounds and then plants pump oxygen back into the atmosphere.

As we are bombarded with pollutants each day, in our water and in the air - installing interior living walls, exterior vertical green - green roofs and living walls, Urban Permaculture - City Gardens, wildflowers and trees - can pay off with significant benefits.

Ultimately, we may live longer.  Ultimately, we may beat the odds with cancer or respiratory diseases.

Restoring Volumetric Green to the Urban Core is critical.  Today, go out and plant a seed or a grown plant.  Bring another inside.  Hang plants from your patio walls and your kitchen window.  Keep plants in your home.  Install a green roof.

Green roofs and living walls - cleaning stormwater, creating habitat, providing a sense of place and beauty and - importantly - fighting disease by removing pollutants!

Surround yourself with plants today.  You may breath better and live longer. 


Remember, the benefits of adding volumetric green to the Urban Core include;

• Cleaning Rainfall runoff and stormwater
• Providing wildlife habitat
• Supporting biodiversity
• Creating habitat for endangered plants
• Integrated pest management - supporting pest consuming invertebrates and amphibians
• Noise insulation
• Reducing Heat Island effect
• Creating a Sense of Place and Landscape Beauty
• and more

Wan to learn more?  Email us here.  We will be glad to help you with your next living wall or green roof design project!

Native Plants for Green Roofs and Living Walls - Seeds For Green Roofs

Great Native Plant Photos on the Seeds For Green Roofs website this morning.  Check out the Lamium and Nephrolepis pictures.

Rooftop Permaculture - GMO, Brassica oleracea Root Architecture

"Gene manipulated corn fields feed people"

The above comment was a response this morning to one of my suggestions rooftop permaculture can help.  It is really sad because some truly believe this.

Fortunately - like the present Middle East changing of the old, stale guard and influx of new ideas, I believe rooftop permaculture and vertical permaculture is well on its way to replacing the old and becoming the new frontier in volumetric and rooftop green.

Green Roof Rooftop Permaculture - Brassica

Green Roof Vegetables - Broccoli

The broccoli here were pulled from the roof garden this week.  We had the Brassica growing in 4" of light weight highly organic composted and very well drained soil on a 4/10 slope.  You can see just how the vegetables became with no additional fertilizers and zero pesticides and herbicides.

Unfortunately, large corporations view rooftop permaculture and the citizens taking the task of feeding themselves back into their own hands as a serious threat to profits.

But I reject the above statement that "Gene manipulated corn fields feed people" as the only successful approach.

Many people may want to eat GMO corn products.  Yet I believe a large portion of the population may not want to.

So I see a grassroots movement arising to support rooftop permaculture, one where common people can make nutritional decisions for themselves rather than having the State or a Large Multi-national Corporation do so.

Check out just how big the Brassica grew.  Look at the root architecture.  We planted them close together to brace against wind issues and ate the greens daily. The plants adapted to the 4" soil (100mm) dispelling the myths of need for deep dirt to grow.

ECHO, see http://echonet.org is a great resource for rooftop permaculture practices, tips and design guidelines from a cost-effective approach.

Our $2.00 worth of seeds provided a daily bunch of organic greens and broccoli tops that would have cost US $ 5 in the store for six months.  As I see it the numbers work out to be close to $1000 savings in food costs, not to mention the health benefits.  That is just for organic broccoli alone.  Add the collards, mustards, sugar snap peas, pok choy, turnips, potatoes, tomatoes and the benefit of fresh air and gardening companionship and one can easily see the economic advantage.

No thank you to GMOs and to the outdated, stale industry guru's that are old news.

Green Roof Sedum Plantings

I am fascinated by the Sedum (Hylotelephilum as some botanists suggest).  They are hardy, drought tolerant, can switch between C3 and CAM photosynthesis and several native species provide food for endangered Lepidoptera species including the Grey Chi and San Bruno Elfin Butterfly.

There are many native Sedum species considered native to  the US.  Some are even protected by law as threatened or endangered as in;

• Pennsylvania
• Oregon, and
• Kentucky

Green Roofs have been shown over the long term to provide great opportunity for the re-establishment of endangered species.  Green Roofs may provide an important opportunity for those threatened or endangered Sedum species to recover.

There is a wonderful American Society of Landscape Architects article on the web focusing on a Green Roof with several popular Sedum species as part of green infrastructure installed to help the Rock Creek Watershed.

The Sedum's used in the project were;

• S. sexangulare
• S. album
• S. spurium
• S. rupestre
• S. tectractinum
• S. floriferum
• S. kamtschaticum, and possibly others.

From a habitat, stormwater, 'sense of place' and heat island effect, this project was timely and ecologically important, and so too were the Sedum plantings.

Yet as you will read, many of these species are potentially invasive and have been recorded on state and organization invasive plant lists.

Importantly however, Sedum should not be singled out as the only invasive or potentially invasive plant when discussing green roofs.  There are many potentially invasive plants that could be associated with green roofs.  Last year we posted a brief article on the use of Nandina spp. on the Gainesville, Florida Regional Utilities Green Roof (thankfully the Nandina was subsequently removed from the planting schedule).

Here in Florida, Sedum have difficulty with Southern Blight Fungus and tend to dampen off during the long hot and humid summers.  In Jacksonville, S. reflexum appears to do the best on living roofs though it too suffers from the humidity.

Sedum propagates easily according to botanical literature and others, as suggested in the Emory Knolls Farms website.  In fact, spreading cuttings and clippings of sedum leaves and stems is suggested as a quick approach to filling a green roof with more plants.

However, some Green Roof companies raise a red flag about invasive species, such as S. sarmentosum where as the Roofscapes, Inc site indicates;


"The only Sedum that might be considered invasive is Sedum sarmentosum, also known as Star Sedum,Gold Moss, Stringy Stonecrop, or Graveyard Moss. It has green spearhead-shaped leaves, lemon yellow flowers, and long tendrils. We do not recommend using this species."

But it is not just green roof plant nurseries that promote Sedum's ability to grow into full size plants from the tiniest of cuttings, other ecological or nature websites suggest the same.

An interesting article and discussion of Sedum and Green Roofs can be found on the Taking Place website where the article entitled Sedum2 mentions of S. floriferum (one of the Sedum species used above mentioned watershed project);


 I’m careful to throw the weeded stems away in the garbage, because the tiniest little bit of stem or spare leaf will root in where it lands and start growing.  It’s not a problem (so far) here, because I do maintain my garden; I wonder about pieces of sedum escaping from roof gardens or green roofs, and rooting in, say, along a river bank or in pavement cracks.  It’s attractive, but it can cover and smother other plants if allowed. 

Importantly, S. sarmentosum has been considered an escaped and invasive species in Japan, subject to numerous studies.

Any plant that roots quickly from leaves and stem cuttings could potentially escape a roof.  Birds carry plant material from the roof on a daily basis.  Here in Florida as well as other windy areas, wind is a strong potential vector of plant DNA.  Fern spores are known to have been carried across the Pacific Ocean on winds, introducing Asian ferns to the Americas.

I suggest, planted anywhere Sedums will escape and start to naturalize.  How bad this naturalization will become is another question.

As a plant biologist my own opinion is Sedum will initially only naturalize within the disturbed environments of the Urban Core of cities such as Jacksonville here in the southeastern US, because of the humidity and Southern Blight fungus issues.  I personally believe it will have a hard time becoming established in the Florida swamps.

Not so the case elsewhere.

Here in the US there are many red flags and concerns now being raised concerning Sedum use and the potential for invasive activity.

For example;

• The City of Indianapolis cautions against the use of both S. sarmentosum and S. hispanico in the Indianapolis Stormwater Green Roof Technical Design Manual
• The Invasive Plant Association of Wisconsin lists S. acre and S. purpureum as having invasive qualities
• Missouri's Exotic Pest Plant list includes S. sarmentosum as a category B exotic present in Missouri
• Virginia's Department of Conservation and Recreation ranks S. sarmentosum as an invasive species
• Massachusetts suggests it is necessary to gather additional data on the S. telephium as part of the Managing Invasive Plants program.
• The Great Lakes Indian Fish and Wildlife Commission list Sedum spp. as a terrestrial  invasive
• Wyoming's Natural Diversity Database report lists S. acre as a noxious weed plant located across F.E. Warren Air Force Base
• New York's state Early Detection Invasive Plant Program lists both S. sarmentosum and S. telephium species
• U.S. Fish and Wildlife Service list S. telephium on their invasive plant list
• S. acre, S. albo-roseum, S. purpureum, S. ruprestre and S. sarmentosum are listed as Alien Plants by Illinois' State Museum site
• USDA Forest Services, Non-Native Invasive Plant List lists S. telephinum/ S. purpureum on their Invasive Plant list
• US Natural Resource Conservation Service maps naturalized and escaped non-natives, including Sedum.  Their database of non-native Sedum species occurrences is informative.  They suggest "These plants are introduced to some part of the PLANTS Floristic Area, though they may be native in other parts. While many are harmless or beneficial, others that are not already invasive or noxious have a high potential to become so in all or part of their range. In general, introduced plants are likely to invade or become noxious since they lack co-evolved competitors and natural enemies to control their populations."  Sedum species listed include;
• S. acre
• S. aizoon
• S. album
• S. dasyphyllum
• S. dendroideum
• S. hispanicum
• S. hybridum
• S. kamtschaticum
• S. linare
• S. mexicanum
• S. ochroleucum
• S. praealtum
• S. refluxeum
• S. sarmentosum
• S. sexangulare
• S. spurium
• S. stoloniferum, and 
• S. ternatum

Other Countries too, view Sedum species as an invasive plant, including;

• Poland, New Zealand, Switzerland
• Czech Republic
• Japan - see above
• New South Wales
• British Columbia
• Ontario Society for Ecological Restoration
• Canadian Wildlife Service
• Mediterranean regions
• and many others

Many Not-For-Profit organizations and preserves also consider Sedum to be potentially invasive. A few include;

• Nature Conservancy of Canada - Garry Oaks Ecosystems lists S. acre as an established invasive species
• Wisconsin Botanical Information System tracks county by county where the many different Sedum species have escaped and become naturalized
• Washington State University Extension Blog has a comment " My plant peeve right now is sedum. It's used and promoted extensively for green roofs and rooftop garden use, because it grows so well in extreme conditions -- which makes it also quite willing to grow in not-so-extreme conditions. I planted a handful that a neighbor had given me, and it now has spread through one garden bed, along the base of a rock outcrop on the other side of the yard (I took a snippet and parked it from the bed onto the outcrop, not knowing how it would spread and spread), and now is moving into the lawn. It's easy to pull out, but a tiny piece will root, so composting is out, and vigilant disposal is necessary. I have yet to see sedum on an invasive species list, but predict that it will show up on a bunch of them in the next few years, as pieces make their way off of rooftops and into the on-the-ground landscape. "
• Mid-Atlantic Gardener's Guide says 'Many smaller sedums are invasive..."
• Grassroots websites suggest Illinois' Draft Invasive Plant documents list both S. sarmentosum and S. telephium are invasive
• The New York Botanical Garden's notes S. sexangulare has been newly noted in the Torrey Range as an exotic species

Yet Sedum will continue to be used across Green Roofs here in the US and the World.

The issue is not really about Sedum.

The issue is one of native plants and exotic, introduced landscape plants.

Do we feel comfortable with the practice to replacing native plants with introduced species because the introduced species are easier to use, hardier and more resilient (maybe because of the lack of natural predators)?

I believe Sedum can be managed appropriately on Green Roofs.  Rooftop growing areas can provide habitat for those native Sedum too, offering protection for those endemic plant species threatened by monoculture takeover of exotics.

The key component to successful exotic Sedum usage is awareness of its plant biology, maintenance practices, local exotic and invasive species management plants, state and federal laws and proper coordination with state and local Native Plant and Invasive Plant organizations.

Many of the lists above are not law.  Sedum is not illegal to use.

The lists above caution us to take account of our practices.

Changing the constituency of Nature can be a dangerous act.

Modeling Green Roof & Rooftop Permaculture Plant Design Performance

As previously stated, light and wind appear to be the primary design variables impacting green roofs and rooftop permaculture.


Understanding how your rooftop garden or green roof plants - vegetables, native plants or other - are impacted by light and wind is very important.


Recall from previous posts, discussions about identification and boundary delineation of  roof areas according to levels of available light and present wind loadings.  The roof under consideration was sectioned off on a five meter grid and assigned design levels of wind and light influence according to the following simplified diagram.  Light and wind can be considered the two primary design factors.

Green Roof Design Diagram

This is not to say the secondary design variables are not important, as they are.  Secondary green roof design variables include:

• Climate and Weather
• Rainfall
• Non-Rainfall Air Water Vapor and Humidity
• Dew, Types of Fog and Frost
• Smog
• Temperatures
• Adjacent vegetation
• Nearby Allopathic Plants
• Adjacent Exotic Invasive Species, and
• Local Seed Source

Though not used to determine the roof polygon boundaries, the secondary variables play an important role within a design model considerations and we will discuss those interactions in detail in future sections. 

Importantly, certain light wavelengths are required for photosynthesis.  Without light photosynthesis does not occur and plants do not grow.  Light is the first primary design variable to be considered when creating roof ecosystem polygons.

Wind is the second of the primary design factors used to determine roof ecosystem polygons.
  

Though ambient outside air temperatures, precipitation, air quality and other design variables are generally consistent across the roof, light availability and wind effects can change depending upon where one stands on the same roof.  Both light and wind are critical factors in designing a green roof for dry and arid climates.  Without adequate light plants will not live and consistently buffeted by desiccating winds plants may cease to transpire and quickly die.


Understanding how wind and light impact the green roof can afford the designer the capability to predict plant growing success.


The following diagram suggests that the optimal growing space on green roofs and for rooftop permaculture lay in areas with moderate to strong sunlight and still to slightly moderate winds.

Green Roof Design Diagram

Finally, understanding the light and wind levels across the roof under consideration can help avoid so-called 'dead-zones'.


Dead zones are areas on the green roof subject to light and wind conditions beyond suitable for most C3 and C4 plants.


CAM and other hardy succulent plants are those most desired for roof areas identified as harsh, a result of too much light and/or too much wind.


Know your wind and light levels.


Your green roof plants will grow accordingly.

Adaptation and Green Roof Plants

We've talked numerous times about the different types of photosynthesis in green roof plants and why understanding those processes are important.  To summarize yet again, CAM plants' stomata usually open only at night to preserve water; C4 plants have multiple and different cells, some deeply embedded within the leaf to fight desiccation; and C3 plants conduct photosynthesis across the leaf surface - rapidly producing carbohydrates but loosing much more water than C4 and CAM plants.

But what is really interesting is looking at collateral issues associated with photosynthesis processes.

Scientists tell us that the majority of C4 plants are typical of prairies or wide open grasslands and these plants developed during periods of earth's history where there were relatively low amounts of CO2.   C4 plants are highly efficient at taking what CO2 and N is available and utilizing both quite efficiently, keeping waste to a minimum.

C4 plant Echinacea purpurea, Asteraceae

C4 plant Echinacea purpurea, Asteraceae

C4 plants interestingly, according to Wikipedia and sources:

represent about 5% of Earth's plant biomass and 1% of its known plant species.^[11] Despite this scarcity, they account for about 30% of terrestrial carbon fixation.^[8] Increasing the proportion of C4 plants on earth could assist biosequestration of CO₂ and represent an important climate change avoidance strategy. Present-day C₄ plants are concentrated in the tropics (below latitudes of 45°) where the high air temperature contributes to higher possible levels of oxygenase activity by RuBisCO, which increases rates of photorespiration in C₃plants.


Wikipedia goes on to state:


C₄ carbon fixation has evolved on up to 40 independent occasions in different families of plants, making it a prime example of convergent evolution.^[8] C₄ plants arose around 25 to 32 million years ago^[8] during the Oligocene (precisely when is difficult to determine) and did not become ecologically significant until around 6 to 7 million years ago, in the Miocene Period.^[8] C₄ metabolism originated when grasses migrated from the shady forest undercanopy to more open environments,^[9] where the high sunlight gave it an advantage over the C₃pathway.^[10] Drought was not necessary for its innovation; rather, the increased resistance to water stress was a by-product of the pathway and allowed C₄ plants to more readily colonise arid environments.^[10]


Additionally, Mycorrhizal fungi associations with C4 plants may help the C4 species adapt to higher CO2 concentrations in the atmosphere.


Nature is blurring the lines between C3, C4 and CAM plants to produce species suited for evolving climates.

Finally, man too is working with genetic engineering and bioengineering to produce those robo-plants we discussed in previous blog posts.

Green roof botany is an evolving science.  Staying abreast of trends, research and discoveries is interesting and can certainly help the green roof designer in developing a successful plant schedule for the green roof project.

Green Roof Drainage, Use of Natural Materials, Arundo Donax Reeds

Per the University of Maryland, Typical Green Roof Soil Media is made from;

• Expanded Slate
• Expanded Shale
• Expanded Clay
• Volcanic Pumice

Amended with;

• Synthetic Fibers
• Fly Ash
• Rubber Foam
• Tire Crumbs

The study goes on to point out that producing 1 cubic meter of expanded slate, clay or shale in the kiln embodies 1.7 million BTU's, producing 110 kg Carbon Dioxide.

Obviously not an ecologically friendly process for a supposedly 'green' product.

The note goes on to point out that during the 2008-2009 time period there were 290,000 square meters of green roofs installed in the three cities of New York, Chicago and D.C., representing a green roof soil media carbon footprint of;

1,148 Metric Tons of CO2

from green roofs.

I thought green roofs were supposed to be at least carbon neutral, and this does not even take into account the carbon footprint of the fertilizers added or the potable water pumped up to and used for supplemental irrigation.

Seemingly, portions of the green roof industry are not so green anymore, possibly hiding behind corporate profits as many other industries are.

But not all green roof professionals are focused solely on profits.  We think there is a strong grassroots effort to move the industry back towards sustainability, focusing on renewable and sustainable building materials and practices.

However there is much established industry pressure to not only continue using high carbon footprint materials, but formalize those materials into required 'standards' - the ultimate monopolizing practice.

ASTM is developing green roof soil media standards as we speak.  There is significant pressure to use these kiln processed, mined earth materials as the basis for all future green roof soils.

Unfortunately, if one looks past profits, there is a real problem with mined earth products treated via heat to make green roof soil media.  The problem is not so apparent in our limited view of seemingly expansive time and space unless we consider the scale.

Using the Galapagos Islands as an example we can see how unsustainable natural resource use has impacted ecology.

Here in the states it is hard to understand ecological impacts from mining because most of us never see what strip mines look like.  There is so much available land that the impact of mined earth products stays out of sight and out of mind.

But in the Galapagos, where real estate is limited in quantity and population pressures increase daily, the problem is easily discernible.

The Galapagos Islands have sustained significant lava stone, beach sand and native timber extraction for construction materials to the point where erosion, loss of habitat and loss of biodiversity was escalating significantly.  Today, the Galapagos' government has strict regulations on the use of natural resources and is making great strides towards preserving their resource heritage.  

Hopefully we can learn from the Galapagos' near environmental tragedy.

Importantly, other green roof leaders from around the world are also looking to use of alternative materials for soils components.

Drainage is an important function expanded mined earth products help facilitate.

A recent project on the south coast of France is utilizing hard native reeds for the drainage components.

The native reeds are used locally for roofing materials and have been proven to last thirty years or longer, about the normal life of a typical roof.

Granted, thirty years life span is not the millennia expanded shale will last, but rather than a strip-mine approach or petro-fired kiln approach, the reeds represent sustainability.

And sustainability is what green roofs are really supposed to be about - creation of habitat for wildlife in the urban core, cleaning of stormwater, sequestering of carbon (instead of creating huge carbon footprints), and offering a sense of place for inhabitants.

Big industry can afford a powerful counter argument as to why strip mined and kiln fired products are really eco-friendly.  But I am not big industry, nor am I an industry organization who is influenced by big industry advertising money.

I can and I will say that green roofs should be based on sustainable practices, using rapidly renewable materials, native plants and ultimately helping the world we live in rather than contributing to a Galapagos like tragedy.

Otherwise, lets just use TPO white roofing to cure heat island effect.  TPO is a whole lot more cost-effective.

Biodiversity, Blown Away by the Actual Proliferation of Nature's Own Green Roof Plants

I was really excited to see a new website/blog Seed For GreenRoofs focusing on learning about green roofs from nature.  Be sure to check out their site here http://seedsforgreenroofs.blogspot.com  The site includes native plants suitable for green roof use from around the world!

We all understand the importance of encouraging and preserving Biodiversity in our environments.  Medicines, food, wildlife, and much more is dependent on ensuring the continuance of all life on our planet, of which many need native plants for food, nectar and survival.  We all are aware of the benefits planting green roofs with native plants.

And there are so many great plants perfectly adapted for green roofs that nature provides for us to use.

Sometimes we just don't pay attention or look at them.  Sometimes we get caught up in the 'just use the green roof monoculture plants' that are so easy to design with.  Sometimes we are unsure what native plants are best to use on a local green roof!

Yet the plants are all around us, and if we'd just look up we could learn.

I have always believed the best way to learn about native and endemic plants is to drive around the downtown section of your local Urban Core and look up, camera and field guide in hand (just watch where you are walking!)

Green Roof plants from Nature, Native Species

So I am not surprised when I find one or two local plants growing in rocks or the mortar cracks around bricks.  These are plants I'll try on a roof.  If they can survive on top of a church steeple then it follows logic that they may also do well on a green roof.

I am happy to find a new species once in a while.

This week when I went to St. Augustine, Florida for a meeting, I parked and walked along the bay over to the old Spanish Fort, Castillo de San Marcos -  constructed from coquina shell and famous for walls that could swallow cannonballs without incurring damage.

I was pretty much awe struck with what I observed.  There was not only one or two plant species growing out of the vertical rock, there were many!  My heart raced!  A true library of potential green roof knowledge lay before me!

As always I am thankful for the internet and the information available therein. And later that afternoon I was able to come across a plant survey of the Fort's walls that indicated over fifty species of plants have been identified growing in the rock walls!

Not one or two, but over fifty different species growing without soil, added irrigation or fertilizer.

This is exciting.

Thanks to Wendy Zomlefer and David Giannasi from the University of Georgia!  Check out their great PDF here.

More info as I sort through the data and analyze for relevancy to the green roof science!

Green Roof Soil Media Note

As standards are being developed by ASTM and other agencies, both private and governmental, here is a reminder to remember High Velocity Wind Areas.

Florida Building Code does not allow loose laid ballast, aggregate, gravel or pavers on rooftops due to hurricanes.

Loose laid gravel or aggregate may become airborne during cyclone winds and damage adjacent fenestration and windows, acting like large shotgun pellets.

Large beds of expanded shale, crushed tile or brick on a roof here in Florida could inflict serious or deadly damage to human life and property.

Parapet walls may be an answer to wind impacts on rooftop aggregate.

Yet the important point here is we cannot rush to adopt an incomplete standard.

A standard that is irrelevant to a geographic area is not a standard at all.

Miami-Dade County has developed agressive testing requirements for high velocity roof applications.  The State of Florida is also working on Building Code requirements as are many of the Florida Universities.

Lets proceed with standards, yet make sure they are applicable.

Green Roof Design - Plant Selection and Integration, Photosynthesis Basics cont.

Plants with C4 photosynthesis processes are now the focus of bioengineering efforts of the worlds foremost plant industry experts.

The C4 Plant Biology Symposium held in Shanghai examined the opportunities of genetically and biologically engineering C3 plants to possess some of the C4 qualities of drought and heat resilience.

The Symposium abstract pdf offers significant insight into the interest of C4 plants' capabilities to survive where C3 plants may not.  Of course, most of the interest now lies in areas of food production (think rooftop permaculture), however horticultural paths, including green roof plant development will soon become a part of the C4 genetic engineering efforts.

As a biodiversity purist I emphatically prefer and recommend use of open pollinated native plant species on green roofs and open pollinated seeds for rooftop permaculture.  But we must take note that the industrial agriculture world understands the benefits a C4 plant offers and we need watch advances in genetic engineering, tracking potential impacts to native plant species and ultimately biodiversity issues.  Keeping abreast of industry trends is important to ensure continuation of biodiversity practices too.

One very clear fact is this:  C4 plants are much more hardier than C3 plants against wind desiccation and dehydration.

Brown, dead Poeaceae C3 species and green, alive Alliaceae C4 species subjected to 48 hr. 1.75 M/S winds

The photo here is of a trial green roof panel, removed from the roof after being subjected to 48 hours of low humidity (approximately 40% relative humidity water vapor) 1.75 meter per second winds, and approximately 12 degrees C average temperature.

The panel is planted primarily with a cool season annual Poaceae C3 species.  There are also several Alliaceae family C4 photosynthesis plugs int he panel.

Remember, the C4 plants, because of their internal structure, loose on average only 1/3 the amount of water during the Calvin Cycle and photosynthesis as C3 plants do.  C4 plants are much more resistant to dessiccation from strong winds.  This is because C4 plants generally conduct photosynthesis by:

• Absorbing CO2 into the mesophyll - 
• Once the CO2 is in the mesophyll it combines with a 3-carbon compound called PEP, phosphoenolpyruvic acid to form a 4-carbon substance called oxaloacetic acid - hence the C4
• The C4 is moved into the deep bundle sheath layer of cells away from the leaf surface
• Inside the bundle sheath the C4 breaks down into the C3 base and eventually PEP for the Calvin Cycle food production

Because the oxaloacetic acid (C4) is moved into the deep bundle of sheath layer cells away from the leaf surface, the C4 plants loose less to transpiration activities from wind and sun action.

Yet there are many additional considerations to integration of C4 and C3 plants on a green roof, including growth rates.  Because C3 plants conduct photosynthesis much more rapidly (remember the analogy between the C3 and C4 plants as a comparison of a large V8 engine vs. a smaller hybrid engine), C3 plants will provide green roof coverage quicker.

Understanding how to integrate C3 and C4 and then CAM species is key to a successful green roof design.  Knowing how green roof plants utilize photosynthesis is key to a successful green roof.


Too many times we in the green roof industry have focused on stone and soil media, plastics and drainage, pumped up additional irrigation and added more and more fertilizers when all we really needed to do is put the right plant in the right place.


Green Roofs should really be about the plants and biodiversity.