Monday, February 28, 2011

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.

Saturday, February 26, 2011

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.

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.

Friday, February 25, 2011

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  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.

Thursday, February 24, 2011

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 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.

Wednesday, February 23, 2011

Green Roof Xericscape Primary Design Variables & Rooftop Polygons

Interestingly, according to the USEPA, Americans use approximately 1.5 billion gallons of water every day on landscaping.  Contrast this over-looked wealth and waste to the realization two hundred million hours each day are spent by families across less developed nations without adequate water infrastructure in securing daily domestic water supplies, some carrying heavy jugs of muddy water on their backs great distances.

Here in the U.S. we use twice as much water for landscaping than the number of gallons of gasoline we burn in our automobiles daily.  With the present U.S. population estimated to be about 311,000,000 persons, landscape water use is on the average about 5 gallons per person per day, or about 19 liters per person per day.  Yet fortunately many governmental agencies are presently encouraging use of native species and wildflowers acclimated to reduced watering or nature based irrigation.

So, if sustainable development practices call for conservation of water in the landscape then irrigation in green roofs should be no hidden exception.  

Because roof ecosystems are subject to significantly harsher biophysical conditions than most ground level landscapes, industry response sometimes has typically been one of adding irrigation and fertilizers to hopefully mitigate additional heat, dryness and desiccating wind stressors typically impacting green roof plants.  Moreover, because the green roof industry here in the US is still relatively young there is a lack of detailed design data to assist in planning and installing nature irrigated green roofs.

Fortunately water conservation practices in green roof design can be simple and cost-effective.   Though one can delve deeply into design theory, effective nature irrigated green roof design theory can truly be best understood with spending time outdoors in and around the project site, looking up and paying attention to what is already there.  We shall see that though we can model design variables in an attempt to analytically predict ‘what works best on a green roof’ sometimes a walk through the town, looking up to see what plants grow naturally in gutters, in the cracks of mortar and across roofs, provides the most useful design information.

To fully understand the design criteria needed for a nature irrigated, native species and biodiversity focused green roof we must first divide the rooftop area into simple polygons that are representative of existing environmental factors.  We want to know where on the roof areas are exposed to harsh, desiccating winds and we want to know where on the rooftop the sunlight becomes either lacking or unbearable.

Understanding these rooftop design variables is made easier through the use of rooftop polygons and there are two abiotic categories of green rood design variables to be used in calculating roof polygons;
  • Primary Variables, and
  • Secondary Variables.
Primary Variables include those variables that may vary based on individual roof polygon, including;
  • Light, and
  • Wind.
Secondary (yet important) variables include those design inputs remaining generally consistent across the roof and not considered in the roof polygon calculation.  They are;
  • Heat Zones
  • Cold Zones
  • Precipitation and Water Vapor Profiles
  • Smog
  • Allopathic Plants Nearby, and
  • other variables.
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.  Understanding where on the roof photosynthetically reactive radiation and light volume measured by Daily Light Intervals or DLI is critical to good green roof design.

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.

Over the next couple of weeks we will be exploring xeric green roof design variables.  First, as an introduction to developing rooftop polygons an Youtube powerpoint presentation is included here for review.

The presentation was used as an introduction for native plants on green roofs but has a solid explanation of rooftop polygon development included.  After reviewing the powerpoint you will have an understanding of rooftop polygon development, and how the two primary design variables can be incorporated into the green roof model.

Further discussion of why light and wind are the two primary green roof design variables will be included in subsequent articles.  Enjoy the powerpoint worksheet.  TOmorrow's post will discuss in length why light and wind are te two primary design variables for green roof plantings.

Tuesday, February 22, 2011

Mid-Day Green Roof Photo - Bio-Char Extensive Green Roof Plants are Up!

Remember the Rabbit Hutch Expansion project?  The Green Roof native wildflowers have sprouted and are growing rapidly!  More soon.. :)
Extensive 40mm Green Roof with BioChar over Metal with Colbond Mat

Green Roof Dead Zones - Why Wind Breaks are Necessary

Green Roof, Extensive - Nature Irrigation via Dew

Green Roof, Extensive - Wind Damage
 Wind is the silent killer of Green Roofs.  Wind can cause more acute damage to green roof plants than a lack of light.  On a chronic basis, light will eventually contribute to stress or death - light is required for photosynthesis.  However strong, desiccating winds can cause plant vascular failure and dehydration within a matter of hours.

The above photos show two edges of a small trial extensive green roof.

The top photo portrays the amount of available water vapor in the form of dew.  As is usual for Jacksonville, we experience prolonged droughts.  It has not rained for a week and we are well behind in our 52 week rainfall accumulation.  However water vapor usually offers a steady supply of condensation on a daily basis.  Click on the top photo for an enlarged view of the green roof plants and the dew condensed on the leaf blades.

The bottom photo shows the northeast corner edge of the 50mm thick green roof.  This edge takes the initial wind impact of most daily winds as the other corners are more protected.  Winds at speeds of only 2 meters per second can evaporate plant leaf water stores faster than the plants vascular system can resupply the leaf with moisture.  Without water, CO2 cannot be absorbed and photosynthesis may not occur.

Additionally, desiccating winds can collapse leaf structure, rupturing vacuoles and other cells causing permanent and possibly fatal damage to the plant.

Surprisingly, many designers do not look to wind as the cause of green roof plant problems.  Yet the wind phenomena is not only restricted to green roofs.  I was speaking to a group of professionals last week and a landscape architect from Orlando mentioned how on busy highways where automobile induced wind currents continually hit landscape plants placed in the median areas, those plants are difficult to keep alive.

Parapets are one answer but how do you prevent the wind induced green roof 'dead zones' from occurring on an exposed roof?

The answer lies in proper integration of wind resistant plants, such as the CAM plants we've discussed.  CAM plants can serve as wind break plants for C4 and C3 interior placed green roof plants.  Remember, for best biodiversity results follow the 10/20/30 rule.  Of course one can design a green roof with wind resistant plants from only one Genus, such as only Sedum, but biodiversity opportunities suffer greatly when rooftop monocultures are used.

All wind exposed green roofs will have perimeter dead zones.

Depending on the strength and water vapor content of the wind, this 'dead zone' can be from 50mm to 50cm in width or more.

Understanding how the wind travels across the roof, and the combined interactions with available light are crucial to placement of CAM plants as wind breaks.

Finally, pumping additional water and adding fertilizer will not solve wind issues.  Know your prevailing wind directions across the green roof.  Design properly with wind resistant plants as wind breaks and you can minimize the effects of winds across green roofs.

Monday, February 21, 2011

Green Roof Vegetables - A List of Recommended C4 Plants

Let's take another look at growing rooftop food gardens.  Rooftop permaculture is a rapidly growing movement across the world.  Highly productive vegetable gardens can be found on green roofs in nearly every city. 

Choosing vegetables that possess C4 photosynthesis capabilities can help ensure rooftop garden success. 

Examples of C4 plants include;

Vegetables & Flowers -
  • Cabbage
  • Broccoli
  • Cauliflower
  • Turnip
  • Mustard Greens
  • Wasabi
  • Cress & Watercress
  • Rapeseed
  • Horseradish
  • Most lettuces
  • Chicory
  • Artichoke
  • Jerusalem artichoke
  • Yacon
  • Echinacea
  • Tagetes marigold
  • Marigolds
  • Zinnias
  • Chrysanthemums
  • Heleniums
  • Artemesia
  • Dandelion
  • Goldenrod, and more
The beauty of C4 plants is their ability to withstand drought and the harsher environment of many rooftops.

Generally, C4 plants loose only one third the amount of water to evapotranspiration as C3 plants, giving them a great advantage on the roof.

Remember, we've discussed C$, C3 and CAM photosynthesis processes in prior posts.  


Photosynthesis occurs in most C3 plants by:
  • 'Breathing' in CO2 and combining the CO2 with a 5-carbon sugar
  • The reaction is facilitated by an enzyme, Ribulose Bisphosphate Carboxylase Oxygenase or RUBISCO abbreviated
  • Now there are 6-carbons
  • The 6-carbon chain breaks into 2 molecules of a glyceric acid called PGA - 3-phosphoglyceric acid
  • The completed reaction is called the Calvin cycle and the PGA is the base for glucose synthesis, along with other carbohydrates
However, some plants have an supplemental or alternative method of implementing the above food production cycle. 

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
CAM plants are different from C4 plants in several ways such as CAM plants taking in CO2 only at night. 

Interestingly, many C4 plants have developed the capabilities to switch back and forth between C3's 'full-steam ahead' photosynthesis on the leaf's surface (where the process can be interrupted by environmental conditions) to the C4 process where the photosynthesis required compounds are protected by layers of plant cells.

The process of switching back and forth between C3 and C4 gives a plant the opportunity to grow quickly, a survival advantage, during good weather and the switch into energy conservation survival mode when extreme and damaging weather arrives.

C4 plants, since the plant's photosynthesis process is protected deeper under the surface of the leaf, are more resilient to drought and extreme temperatures.

Therefore, under certain conditions and when placed in certain roof locations, make very good green roof plants.

Realize however, green roof plant selection is modeled on many inputs, C3, C4 or CAM type just being one factor.

However the green roof plant designer must understand the difference in the photosynthesis processes taking place in the plants being specified on any green roof.  

There are many interesting discussions about  C4  and C3 plants and climate change.  We will reserve a future discussion on insights into whether C3 or C4 or CAM plants will have an evolutionary advantage in the future with increased levels of CO2.  Surprisingly - no - not so surprisingly, 'Mother Nature' always steps in and provides adaptation mechanisms.  We will discuss these adaptations both C3 and C4 plants implement to survive either higher or lower levels of CO2.

Having moved through some heavy technical facts on C3, C4 and CAM plants we hope the discussion has not been too boring.

The real photosynthesis processes are much more complicated than we've talked about in these articles.  Understanding the basic differences between C3, C4 and CAM plants will allow the green roof plant designer to greatly increase survival opportunities for their green roof design.

Happy Green Roofing!


Friday, February 18, 2011

Green Roof & Rooftop Permaculture Jump Start on Seeds!

Friday tip of the day!

DIY, Cost-effective method for starting seeds indoors for the greenroof or rooftop garden.

Find old kitchen cabinet or dresser drawers and line the drawers with a garbage bag or other recycled waterproofing liner.

Add seed starting mix and plant seeds, water lightly and place on top of the refrigerator. The heat from the refrigerator will assist in germination!

When the snow and ice melt from your roof and the rooftop garden or green roof are ready for planting, your green roof seeds will be also.
Jump Start of Green Roof and Rooftop Permaculture Seeds

Thursday, February 17, 2011

Foggy Morning Green Roof Garlic Photo

Quick green roof update photo.  The Allium sativum is growing rapidly!  I've tasted a few of the garlic greens and they are delicious.  Fed some to the rabbits, too who quickly devoured the strong sulfur flavored and medicinally important, allicin containing leaves.

Medicinal & Food Green Roof for Rabbits
Recall, the greenroof system is constructed with a 50mm recycled and structural polypropylene frame embedded with a non-woven geosynthetic fabric and compost for a nature irrigated, hydroponic-type planting bed.  The structural characteristics of the roof allow for spanning between the wooden rabbit side braces and a 20 mil HDPE liner keeps the rabbits dry.

Cost-effective, lightweight, nature irrigated green roofs are becoming more popular as understanding of water shortage crises spreads.

Rooftop food production also is increasing in popularity and importance as open space diminishes and rooftop acreage proliferates!

As always, we welcome your comments and emails and Happy Green Roofing!


Wednesday, February 16, 2011

Rooftop Vegetable Garden Mid-day Photo

Grow Your own Organically on the Roof!
Delicious!  Organic!

Grow your own on!

Green Roofs, the New Frontier for Exotic and Invasive Species

A couple of interesting Save the Date Type reminders:

The Pine Lily Chapter of the Florida Native Plant Society will be holding a presentation on the use of Native Plants on Green Roofs, February 17th in Kissimmee, Florida. Details Here.

The Florida Exotic Pest Plant Council's 26th Annual Symposium will be held May 17th - 20th, 2011 in Maitland, Florida where the theme is:

Exotics on the Run: Leveling the Playing Field for Native Plants

I'll be providing a presentation entitled: 

Florida Green Roofs, The New Frontier for Invasive and Exotic Species. Case Studies from World Green Roofs.

Save the Dates! 

Alternative Drainage Systems for Green and Living Roofs

Green Roofs have existed for as long as man has here on Planet Earth in one form or fashion.

Today we see the majority of green roof drainage systems created and manufactured from petroleum based chemicals.

Notably, there is a difference in using recycled content in a plastic and reusing the plastic.

Recycling recently has come under varying levels of scrutiny with respect to the morality of low overseas sweat-shop type wages in both the recycling facility and then the low wage, sweat-shop plastics molding facility.   Certainly though the idea of recycling plastics is a good idea.

Reusing plastics, on the other hand is quite sustainable.  Reusing available materials, as is a focus of the many green building programs, prevents materials from ever reaching the landfill without an additional step of shipping overseas, grinding, melting and re-molding.

Issues with reusing plastics include; consistency and quality control,   The same issues exist with re-ground and re-molded plastics but on a different level - one easier to quantify in technical terms.

Kent Thompson, a Green Roof Professional here in the states commented on the Capitol GreenRoof Discussion board about a demonstration green roof using reused drainage material.  Kent writes:

"Currently, I'm building a demonstration roof with upside down nursery flats filled with styrafoam packing peanuts (not the newer biodegrable variety) as the drainage layer.  Both of these materials were diverted from the waste stream.  I doubled up the flats for extra durability during installation.  The flats have several holes drilled in each side and are imperfectly adhered to the waterproof membrane to facilitate drainage. "

I added several thoughts, including; published an article about a zero C eco-village where egg cartons were used as drainage in the green roof.  The article can be viewed at 
Another interesting 2005 article briefly discusses the historical use of reeds and tar for green roof bases
Country Smallholding published information about historical roofing materials, including reeds and waterproofing & drainage for old turf roofs here:
I admire your initiative to try the inverted trays & peanuts.  Excellent effort - keep us updated on the results.
Dusty Gedge of is a great resource - he is in the UK and has knowledge of most European efforts.
If you are on twitter - check out  Green Roofs in France - I know they are very familiar with reed construction and are doing a small green roof with reed drainage system now.  Some water reeds are said to last 50-80 years. 
I really appreciate everyone's comments here and hope for more as it is very beneficial to my understanding.
Transparency is always the best approach.  If we use plastics for green roof systems and those plastics are molded in low wage shops and contribute significantly to local pollution somewhere across the globe, we should acknowledge that.
If the plastics are recycled locally and sustainably we should acknowledge and applaud those sustainable results.
If the plastic drainage systems are virgin petroleum based we should acknowledge that too.
Asking ourselves the hard questions always leads to success and improvement.
As I stated many times before, I am not ready to give up on plastic components.  I still use plastic systems and am very happy with the performance.  
Yet it would be nice to be able to rightfully be proud the green roof system was constructed in a sustainable manner.
As always, we look forward to your comments and emails.

Happy Green Roofing! Kevin

Tuesday, February 15, 2011

Designing Green Roofs with Native Plants, A French Living Roof

Native wildflowers and plants offer much more than cleaning stormwater and providing habitat.

Most importantly, their inherent beauty creates a 'Sense of Place' we all long for.  This 'Sense of Place' desire is an emotion that is embedded deeply within our DNA and as a population it has only been but a small fraction of time that we've lived apart from nature in the Urban Core.  Wildflowers and Homo sapiens have had a close relationship since the dawn of time.

Moreover, in addition to the intrinsic beauty a planting of native wildflowers adds to a rooftop, the plants also create habitat for wildlife, clean stormwater, sequester carbon, pump out fresh oxygen for us to breath, help cool the cities and more!

In conversation with one of the pioneers of French Living Roofs using native plant species I was fortunate to obtain a proposed and draft species list for an extensive (approximately 100 - 120 mm thick) vegetated roof for biodiversity.

The designer, Pescalune (you can follow on Twitter ) in conjunction with Dusty Gedge from Living Roofs are designing an extensive living roof system that takes advantage of local native materials.  Dusty can be followed on Twitter at

Being privy to the potential native plant list, I could not help but quickly draw a sketch of what the natives may look like en masse when blooming.  Granted the plants will not bloom all at the same time however many flowers will be open concurrently. Not to scale, but you get the general idea of beauty.

Green Roof France, Toits Verts Pour Le Pescalune
The plant species list under consideration is interesting because many of those cultivated species here in the States are found growing naturally in France.

Potential Green Roof France natives include:

·    Aster tripolium L. Sea Aster
·    Borago officinalis Borage
·    Calendula officinalis Pot marigold
·    Crocus, Wild Crocus
·    Dittrichia viscosa, False Yellowhead
·    Erysimum cheiri (syn. Cheiranthus cheiri) Aegean wallflower
·    Fumaria officinalis Common Fumitory or Earth smoke
·    Lamium Deadnettle
·    Limonium vulgare, Common sea-lavender
·    Ornithogalum umbellatum, Star of Bethlehem
·    Papaver rhoeas, Corn Poppy
·    Phacelia tanacetifolia  Lacy phacelia.
·    Plantago lanceolata Ribwort plantain
·    Portulaca oleracea Common Purslane
·    Scabiosa, Scabious
·    Spergularia marina, Lesser Sea-Spurrey
·    Taraxacum officinale, Common Dandelion
·    Trifolium pratense L., Red Clover
·    Urtica, Nettle
·    Veronica chamaedrys L. Germander Speedwell, Bird's-eye Speedwell,
·    Viola

Others under consideration are:
  • Chamaemelum nobile, Roman Camomille
  • Melissa officinalis Lemon balm 
  • Satureja
  • Origanum majorana Marjoram
  • Eruca sativa , Rocket
I love the way the Arugula is called 'Rocket'!  

Considering a living roof?  You might just want to consider using wildflowers and native species endemic to your site.

As always, feel free to email us with comments and questions.

Happy Green Roofing!


Monday, February 14, 2011

Photo Example of Why Green Roofs Support Biodiversity

Arugula is one of my favorite Green Roof vegetables.  The plants are going to seeds here now, blooming and all the honey bees within miles are coming to feast on the nectar.
The rooftop permaculture garden is swarming with life.

Without the green roof there would be only asphalt shingles.  No bees.  No flowers and no delicious arugula for salads and sandwiches. No pollination and only GMO seeds.

Providing habitat and supporting Biodiversity in the Urban Core.

Green roofs supporting Biodiversity.

Green Roof Arugula Supporting Biodiversity

Sustainability, Florida Green Roofs and Living Walls, Urban Permaculture - A Rambling Editorial

Sometimes I think I am truly evolved into a sustainability expert.

Then my eyes are opened and I wonder "why am I still so 'plastics' oriented?

Saw Palmetto 'Living Wall'

We are building a chicken coop.  The twelve Rhode Island Reds are about ready for the coop and I am about tired of them being in the kitchen.

The chicken coop is all wired in and ready to go except for the shade cloth I thought about hanging shadecloth over the nests and ends of the coop for relief from the hot Florida sun.

Plastic covered the wire frame to keep the rain out.

Saw Palmetto 'Green Roof' for Chicken Coop

Saw Palmetto Interior View Living Wall

Shade cloth is woven from petro-based chemicals and contributes to peak oil issues, and ultimately is expensive - costing about $200 to cover the coop.

However I ams so trained to think 'industrial'.

Amazingly, nature has presented me with numerous opportunities, year after year of my life to learn recycling and sustainability.

Something in my mind is programed to always say - 'Go to the Home Improvement store, Kevin! There is a plastic gadget you need for this project!".

I know I should recycle.  I think constantly about how the Green Roof Industry can move away from industrial plastic and complicated layer after of layer of 'things' on the roof just to grow plants.

And I have this 'plastics is better' concept drilled into my head s o often, I am almost fearful of exploring alternative methods and natural materials.  "Organic' and 'Natural' are a bad deal and at best will not last but a year or two then fail and create massive liability.  Best go with multiple layers of plastics.

It is as Krishnamurti says about requiring a 'mutation of the mind' to change, yet my mind is molded into channels of 'plastics' and 'petro-based products'.  In the rush to push what I believe to be very important for food supplies in the Urban Core - Green Roofs and Rooftop Permaculture - I fall trap to the 'petro-based systems.

Besides my Biology degree, I am trained as a lawyer and quite 'tort' alert and though I everyday hear negative and questionable comments from the industry about natural materials, I am more concerned about what I am doing with my plastic consumer mannerisms than I am about failure from natural materials.

You see, despite what I've been brainwashed with about how much better plastics are, I can look around and see green roofs and living walls and structures made from natural materials many years older than the relatively new 'plastics' based systems in vogue today.

The argument about natural material based systems requiring annual or periodic maintenance and replacement comes into mind.  However, all green roofs and living walls require  periodic maintenance.  I've yet to see a green roof or living wall be maintenance free - in fact many are maintenance intensive!

How do I change my plastic mindset?  Have I truly gone so far redemption is improbable?  Will it really take a major mutation of my thought process?  I think so.  We are hopelessly lost to plastics.

Unless we can step back, and as Khrishnamurti says:

"It is only when the totality of the mind is still, that the creative, the nameless comes into being."

My problem is I am too Type A, always too busy building a green something or other.  My mind can never be still and so will always probably be thinking first, 'Plastics!'  But I have learned to listen.

When talking about the chicken coop shadecloth Judy said simply, 'use Saw Palmetto - it is free, sustainable and will work better for not only is it providing shade but the insects attracted to it will provide food for the chickens!.'

We have lots of saw palmetto at the back of our lot.

Though not truly a green roof in the sense of living plants (though I could create a supportive argument :)) the living wall and green roof of saw palmetto is quite sustainable!  In fact, I never should have covered the coop with plastic in the first place - just used the saw palmetto.

Tell those gone on before us who used saw palmetto for centuries it is not an appropriate or traditional building material.  Unfortunately I doubt if there is a Saw Palmetto lobby in Washington to compete with the plastics lobby.

I think we've really gone too far with rampant disregard for nature.  May be too late for the major mutation to occur so we are working here and across the Urban Core with Green Roofs and Rooftop Permaculture to make as soft a landing pad as possible.......

Sunday, February 13, 2011

Biodiversity, Patterns, Randomness and Green Roofs

Having walked and waded through Florida's swamps most of my life, I've had to always watch for alligators, poisonous snakes and biting insect nests.  Swamp trekking involves slow tedious movements, especially if the water you are walking through is dark and you cannot see what you are stepping on.  Logs, holes and other obstacles often times lie just under the surface making a fast get-away nearly improbable.

Importantly most of the potentially dangerous animals in a swamp are non-aggressive unless bothered.  An alligator typically (I say typically because there have been known aggressive and fatal attacks) won't bother you unless it feels threatened.  Same way with rattlesnakes and stinging insects.

Now I will say a water moccasin is a mean creature and just as often as not they will chase you.  Pushing my way through three meter tall saw palmetto along the edge of a creek one day I had a large water moccasin, Agkistrodon piscivorus, jump out of a saw palmetto, Serenoa repens, and begin striking at my legs.  In my attempt to retreat I tripped and fell into the water where the snake continued to pursue after me and left with the choice of dispatch with my machete or have the moccasin bite me between the legs I cut the reptiles head off swiftly.  Unfortunately, the snake's aggressiveness is embedded rather strongly within its DNA and the severed head continued to jump and strike for most of a minute, quite frighteningly.

I say all of this to make a point about biodiversity and green roofs.

One of the many things I've learned from the swamps is a subconscious awareness of patterns.  When I am in the field where dangerous animals are located I look for patterns.  In the plant community there are few large geometric patterns other than the flower.  But on the ground plant habitat is always random in visual nature.  However, when my eye catches a glimpse of a solid geometric pattern in length, width or height I immediately look to see what type of animal I am approaching.

A Eastern Diamondback Rattlesnake, for example can kill an adult quite quickly with its potent venom, yet this snake just wants to be left alone.  So if I am in a thicket of plants and look ahead to see the distinct pattern as portrayed here in Wikipedia, I change my path so as not to interfere with the creature.

Plant communities will always exhibit more randomness in their visual patterns than animals.  This is true even when walking through a seemingly uniform pine flatwoods area covered in meadowbeauty or wire-grass.  The habitat may seem uniform yet there is the randomness of spacing between the pines and between the plants.

Recognizing patterns has saved me from stepping on a still lying 'gator' many times.

And the random beauty of plant communities, the lines, curves, colors and hues is nature's way unique way of fingerprinting - everything is unique.  There are no exact and identical plant formations in nature.

Complicated uniqueness is the focal point of bio-diversity.  Each plant system or wildlife community is diverse in biological constituency, hence the tern 'bio' - 'diversity'.

A nature-focused, native species green roof should be designed accordingly.

The subtle inundation's and changing ground elevation lines should be reflected on the roof.  Green roof soil media gradations of 10 mm to 50 mm across a relatively flat stretch of roof are important.  Elevation changes in living roof soil media provide much more than visual interest - they serve as wind breaks, assist in the collection, transport and storage of rainwater, dew and fog and provide shelter for visiting wildlife.

Too many times we may simply rake a green roof sol media flat.  Allowing slight fluctuations in the soil media mimics nature and ultimately may allow for more chances at green roof community planting successes.

The same holds true for species mixes on green roofs.  The general rule for a nature-based biodiverse planting is the 10-20-30 rule.  The 10-20-30 rule guides us to plant no more than 10% of the green roof with any one Species, 20% of the roof with one Genera and 30% of the roof with one Family.

Monoculture plantings on green roofs are confusing to wildlife and provide sub-standard communal and foraging habitat.

And while it may be easy to call out in design the one or two proven plants for a green roof project, the long term habitat value will be diminished with a green roof that only contains one type of plant.  Remember, even if the design intent is to have a solid, one color and one texture appearance across the roof, this can be accomplished with using a mix of similar appearing species.  One does not have to create monocultures on green roofs to achieve design intent!

Learn to recognize patterns!

A good, biodiverse green roof planting design should afford stunning random beauty.  The Jackson's chameleon's tail may be coiled in a recognizable pattern and the sharp eye will find the photo opportunity amidst the randomness of the green roof plantings.

Bio-diversity on green roofs, restoring habitat to the Urban Core.