Florida Extensive Green Roof Systems, Green Roof Depth Considerations and Root Architecture

I ran across an interesting article in the American Journal of Botany entitled 

Root deployment and shoot growth for two desert species in response to soil rockiness by Gretchen B. North, Edward G. Bobich and Park S. Nobel.

The article confirmed interesting data we've been seeing with respect to root formation in coarse and shallow green roof soils.

MetroVerde Green Roof system, shallow, extensive and well-drained

Shallow green roof soils work well for us  we believe, for a number of reasons, including;

1. Except for the rare lengthy, monsoon-like downpours that occur annually and deliver the false impression Florida is more rain forest like than desert, water penetration into green roof soil media is minimal and lengthy periods of drought are frequent.  Therefore growing systems that force shallow root growth also promote stronger rainwater contact for those light drizzles we may experience.

2. Shallow growing systems combined with appropriate soil media enhance root-oxygen contact.  Root-oxygen contact importance has been especially shown as important through agrinomy studies in hydroponics.  Shallow root systems on extensive green roofs allow for increased oxygen uptake leading to significantly more biomass production.

Agaves and Yuccas are some of our standard green roof plants for use here in Florida.  There are two agave species native to Florida (and the Southeastern U.S.) - they are false sisal (Agave decipiens) and wild century plant (Agave neglecta).  Native Yuccas include:  Spanish bayonet (Yucca aloifolia), Adam's needle (Yucca filamentosa), and moundlily yucca (Yucca gloriosa), and curve-leaf yucca, Yucca recurvifolia.

Though the paper looks at Agave deserti and bunchgrass, Pleuraphis rigida, the concepts and conclusions are important.

Observations included:

1.  Water potential was higher in sandy soils than in rocky soils.

2. Agave deserti preferred rocky soils and was absent in pure sandy soils.

3. Root growth was greatest in sandy soils 

4. Agave deserti had twice the biomass and root surface area in sandy soils over rocky soils (example of environmentally induced acclimination)

5. Agave deserti leaf's water potential was the same at rocky and sandy sites but the transpiration rate was twice as high in rocky soils.

Conclusions and assumptions Green Roof Designers can use are:

Certain agaves (and yuccas) growing in well drained soils (rocky instead of sandy) exhibit acclimation characteristics of slowed growth rates and biomass production.  Slow growing plants on the green roof may be  more likely to survive long periods of drought.

Agave root architecture will develop slower and more shallow in rocky soils than in sandy soils.  Again, on an extensive green roof - one with relatively shallow soils - a plant with a shallow root system does better than a plant requiring a deep root system.  Agaves can acclimate to the coarse soils. Again, a shallow root system plant may be preferable over the deep rot system species.  A deep root species may have the tendency to assert agressive root barrier or roofing membrane attack.

Agaves do not want wet feet.  Where there is an over-abundance of moisture (very sandy soils) agaves may not be present.  Keep the green roof well drained.  This concept is in general disagreement with the school of thought that green roofs should serve as stormwater retention volumes or basins in conjunction with cisterns.  We've made the suggestion many times that due to Florida's water crisis, an irrigated green roof may not be considered sustainable - as one third to one half of the year it will end up irrigated with potable (during times of drought).  Within rainy season periods one will being irrigating the roof more frequently to empty the ever filling cistern - thus exposing the agaves, or any slow growing and green roof tolerant plant to 'wet feet' conditions.  Keep your green roof plants in conditions that do not generally comprise long term saturation.

Rocky soils may have a tendency to absorb and capture more dew than sandy soils.  This assumption/conclusion has many important implications for green roof plants water needs.  Because air can flow more easier through rocky soils, the dew has a tendency to penetrate to rockier soils.  Sandy soils may block moisture laden air.

I like to compare the ability of rocky or coarse soils to capture dew to the summer morning wet grass in your front yard.  There will always be more visible dew on the high surface area grass blades than say, on flat concrete.

Capturing all the water  from dew, fog and slight drizzles is important for our approach to green roof design based on non-potable irrigation.

Nature is always the best teacher.

Ethnobotany for Green Roofs, Achillea millefolium, Yarrow on Florida Green Roofs

Rooftop ethnobotany should be a part of all green and living roofs as plants have given humans food, fiber and medicine throughout the ages.


One of my favorite green roof plants rich in ethnobotanical history is Yarrow.

Green Roof Achillea millefolium, ethnobotanical wonder and living roof beauty

Yarrow is a hardy Northern Hemisphere native wildflower suited for hot, dry green roofs. Yarrow is found growing as a native plant around the world in the northern hemisphere. 

Her Mexican name is plumajilla or ‘little feather’ due to the feathery shape of her leaf.
Important to biodiversity support, many birds (including sparrows) use the soft leaves of the plant to line their nest.  The leaves are quite soft and add a blanket of light green color across the green roof for much of the spring and early summer.  When the blooms began to appear during late May and June the plant sends up shoots, supporting beautiful umbells of flowers. 

Green Roof Achillea millefolium, Breaking Ground Green Roof

Yarrow has a rich ethnobotanical history having been used for centuries as a wound herb, and is famous for the capability to stop bleeding from cuts. The leaves may be used as a spinach like vegetable, cooked or in salads.  The plants has also been used as a flavoring in beer. Yarrow has EO data suggestion insecticidal qualities against common mosquitoes.

MetroVerde Green Roofs supporting biodiversity on many levels, Yarrow

Yarrow can tolerate hot, dry soils with little organic material.  A member of the Asteraceae family the plant is very drought tolerant once established. The flowers add a variety of surprisingly bright color to the green roof as many other flowering plants are seeding out and loosing their color.  The perennial plant usually comes back and flowers reliably, year after year.

During the harvest season when most green roof plants are beginning to wear a tired look from summer's heat and humidity, Yarrow is just beginning to develop a rich, deep rainforest-like green hue.

Shown growing here with Pennywort, Hydrocotyle spp. and Aloe, Yarrow serves as a weed blocking  groundcover worthy of any living roof.

Another Florida Green Roof and Sedum Note - Vernalization

I am daily emailed about sedum and Florida Green Roofs.  Today you will find my brief answer to an interesting perspective someone emailed me concerning Florida Green Roofs and Sedum.

Sedum devoured by Southern Blight Fungus

The question was focused on Sedum and vernalization.

Below is my response.

I am certainly the wrong person to ask about success with sedum.  I have tried for years in Florida with zero success.

We now believe the humidity, combined with other environmental factors such as fungi create such hostility towards the plant that she will not grow reliably on roofs here.

Most people in the green roof industry I speak with say they will not try and use sedum below a certain latitude - they typically say that when you are coming south and see the dominant tree canopy change from hardwoods to pine trees.

The sedum I've had the most luck with is the 'Blue Spruce' variety, Sedum reflexum.  Yet this variety of sedum does not thrive and simply 'hangs on' longer than most other varieties.

Because sedum is propagated primarily by cuttings and rootings vernalization is not a survival issue here, in my horticultural opinion.  I see many plants, such as Bradford pear, Pyrus calelryana, for instance grow quite well here - they simply do not flower.

There are two primary suspects, in my opinion that afflict sedum here and prevent the plant from surviving year after year on the roof.  They are:

1. Sclerotium rolfsii aka Southern Blight Fungus (see a post about Southern Blight here), and

2.  Pseudomonas bacteria (another post re Pseudomonas here)

There are many other plants such as Aptenia, Delosperma and others that respond the same way.

One way to avoid the fungus and bacteria is to use sterile soil.  But as soon as a bird drops or wind blows debris onto the roof the Sclerotium establishes residency.

So rather than continue to battle trying to use this non-native plant on roofs here, I find better use of native plants and wildflowers who the local pollinators and wildlife value much more highly than the sedum.

I am sure someday GMO technology will create a super sedum for Florida. 

Sometimes information on what hasn't worked is just as important for Green Roof technology as are success stories.

Hope this helps!

Green Roofs in Florida

Lots happening in Florida with respect to green roofs.  To bring you up to speed here are a few noteworthy items of interest:

Genora Crain-Orth will be interviewed on public radio this morning here in Jacksonville about her efforts to secure permission for a small green roof on her historic home.  The interview will be aired at 9 am EST and can be heard online around the world from WJCT, First Coast Connect'd live stream.

Genora's living roof may be small but the impact is important.  She has placed a vision into action.  Those visions we have, once placed into action can change the world.  You can also read more about Genora's living roof here.

Secondly, Sustainable Florida is hosting the 2011 Sustainable You conference in Tallahassee this week.  You can see the green roof presentation slideshow here!




Thanks to Breaking Ground Contracting for use of some great slides and photos!

Thirdly, a live video filming on the Breaking Ground Green Roof will be taking place Thursday, October 27th, 9 am EST.  The focus will be on the newly emerging winter food crops.  Interested adults are invited to attend by RSVPing Catherine Burkee.

Jimmy Sterling and I are headed to South Florida next week to design a 6,000 sf rooftop garden!

The Jacksonville Zoo green roofs are coming up in November!

Florida is leading the way in the south for green roofs!

Green Roof Photos for a Florida Friday Morning

Green Roof plants seem to love the respite from the harsh summer temperatures.  Check out these flowering beauties.

Green Roof Roselle bloom, Hibiscus sabdariffa, tea & ethnobotanical plant

Florida Green Roof calabasa

Early morning Florida Green Roof cosmos

Green roof early morning pink muhly native grasses

Green roof early morning pink muhly native grasses

Green Roof Design - Biaxial Geogrids, Wind and Water Erosion

Here in hurricane or cyclone alley we have always recommend use of a restraining weave embedded in green roof soil media.

I like the thick three dimensional weaves of non-woven geogrids.  Those offering multi-axial reinforcement are even better.  However sustainability probably lies in coir or hemp and not in the nylons and polypropylenes.

Regardless, three dimensional weaves have a huge impact on erosion control for green roofs!  Check out this video!

Green Roofs, Backyards and Hens in Jacksonville - An Ordinance Change.

Rooftop Urban Ag is coming.  I am seeing more and more rooftop beekeeping and of course, pigeons have long occupied building tops, along with other birds and fowl.  As always, Europe is light years ahead of us here in Florida with respect to hens on the roof.  Except for Nichole & Matt.

Chickens too could be integrated into balconies, across roofs and especially on planted, living roofs.

Be sure to check out this really cool website discussing Green Roofs for chicken coops and the 'Omlet' Coop design.

There is a really strong grassroots urban agriculture movement happening here in Jacksonville and in other cities across the U.S.


Of course, I am working to design a cool (temperature-wise) rooftop coop capable of withstanding hurricanes.

We are asking everyone for their help in legalizing fresh eggs for our families.

So I thought today we'd look at a few FAQ's concerning hens and dispel a few rumors and misconceptions about hens, and clarify a few others.

Here in Jacksonville, backyard hens are not allowed under present code.  This doesn't mean they don't exist.  In fact, Jacksonville has a rather large domestic hen population.  Chickens are literally found in every neighborhood, rich and poor.

If you want to follow our efforts like the Facebook Page or sign the petition located here (HensInJax)!


Here a few questions I normally hear when people start discussing backyard hens.

Jacksonville Backyard Hens FAQs.

Are roosters required to  make eggs?


Nope!  Fresh hen eggs are healthy to eat, a good source of protein and important to feeding the urban core residents.  We get four to five eggs per week per hen (eggs without hormones and other drugs).  The eggs you buy in the store may be months old.  Backyard or rooftop hens allow for daily freshness.

Are backyard hens noisy?

Roosters are loud, however we are proposing to prohibit roosters under the ordinance we are writing.

I think hens are quiet but chatty creatures.  Listen in on ours during egg laying sessions.



Are backyard hens dirty? Foul fowl?


Depends on the caretaker.  Is your dog dirty?  Is your cat dirty?  All depends on how well you care for your animals.  I find hens are exceptionally clean, much cleaner than dogs or cats.  And they are the very best at catching pest bugs hiding in the yard for snacks.  I see no termites, roaches, flies or ants in our coop!  Got rooftop bugs?  Turn the hens loose...

Do coops or hens smell?


Nope.  But I keep mine clean as we do with our dog's rug.

Do we  propose to let hens run free?


As a pet or backyard hen owner you are responsible for keeping all your animals in your yard.

Do hens attack?


Hens are extremely docile creatures.  They like to be petted.

How long do hens live?


Typically a couple years up to six or so.

Do they attract rodents or raccoons?


Processed food attracts rodents, including compost scraps, or dog and cat food.  If you have a moveable hen tractor type coop then the birds can keep your lawn mowed instead of using lots of processed food.  Keep the food areas clean!  Rodents and raccoons will not catch a bus and come into town in hopes of finding hen food.  If you have rodents or raccoons in your hood, then they are already there.  I have never once seen a rodent in our backyard coop.

What about eating the hens?


The ordinance we propose contains a 'no-kill' clause.  Go to Whole Foods for fresh hen meat.  I prefer the vegetarian route.

Why are you proposing another Ordinance that will create a potential problem here in Jacksonville?


Hens can already be found across the city in large numbers and are readily for sale at the local feed and garden centers.  We want to legitimize a very large existing issue, not create a new one.

What about pigs and cows?


The existing ordinance addresses only backyard hens.

Are hens considered 'gateway' fowl - leading to desires of keeping pigs, cows, bears, camels and other animals?


Are you lucid?

What about other cities across the U.S.?


Most other cities across the world and the U.S. allow for a limited number of backyard hens.  You can find reference to and summaries of other cities Urban Ag code here.

Here is the backyard domestic hen language we are proposing for Jacksonville:

The keeping of domestic hens is permitted outright on lots zoned for a single-family dwelling as an accessory use to any principal permitted use.

Up to six (6) domestic hens may be kept per single-family lot.

Enclosing structures for domestic hens shall be provided and shall be screened from street view.  

Enclosing structures shall comply with Section 656.403 and shall be consistent with setback requirements.

Structures for domestic hens and flock care shall be consistent with University of Florida, IFAS Publication AN239 Basic Guide for the Backyard Chicken Flock as amended.

Roosters are not permitted.

Killing and dressing domestic hens is not permitted except at a permitted processing facility.

More soon!

Kevin

Florida Green Roofs for Lepidoptera

Florida Green Roof attracting Lepidoptera, at Breaking Ground Contracting by MetroVerde

Over the years I've noticed butterflies always attracted to green roofs, especially those living roofs using native wildflowers.

Florida Green Roof attracting Lepidoptera, at Breaking Ground Contracting by MetroVerde

I think I am going to start calling my living native wildflower roofs, 'Butterfly Roofs'.

Florida Green Roof attracting Lepidoptera, at Breaking Ground Contracting by MetroVerde

Time after time I ascend the ladder or stairs to a green roof to a dance of butterflies across flowers of the sky.

Florida Green Roof attracting Lepidoptera, at Breaking Ground Contracting by MetroVerde

Here, a Gulf Fritillary dances about the green roof zinnias.

Butterfly Roofs!  I like the name as much as the Gulf fritillary likes the flowers on the Breaking Ground Contracting Green Roof!

Green Roofs and Food Freedom in Florida

Green Roofs and all other types of urban agriculture provide food freedom.  Food freedom is essential to our health, security and commerce.

The other day I was meeting with Jimmy Orth and Amanda Searle concerning our urban agriculture efforts here in Jacksonville.  We were discussing strategy and successes over tea in Jacksonville's Uptown Market, a wonderful restaurant committed to buying local food.

Early morning Cosmos on the roof

Looking out the window, the tall Jacksonville Electric Association (JEA) tower framed the urban skyline. JEA has been a progressive member of our community, bringing grants, ideas and technology to help reduce energy consumption and clean the environment.

Electricity and water and sewer services though are truly a monopoly.

We only have limited choices from where we purchase utilities.

I wondered of one day food would be treated in the same manner, sold and distributed by an association with a tall urban tower.

Hope fully, small green roofs and what I call 'Square Inch" urban agriculture will flourish so that food monopolies will not materialize in the urban core.

But it is up to us to make sure our food stays legal and is grown local.

There are many benefits associated with and reasons for growing rooftop gardens.  On the average, food on our typical dinner table travels 1,500 miles in the back of a tractor-trailer rig to reach our mouths.  This is not sustainable.

Yet many urban dwellers do not have the yard space to grow food.  This is where living walls and green roofs find their food value.  Most everyone has a balcony or roof area.  Maximizing growing efficiency in the smallest of spaces can produce proliferate amounts of edibles.

Green roof technology has progressed to the point where prodigious amounts of veggies can be grown in three inches of soil media.  The science of hydroponics is also contributing importantly to urban agriculture.

Start by planting a bunch of greens in your gutter.  Find a bucket and create an herb garden in it with rags and compost for soil.  You don't have to go out and spend thousands of dollars on big, fancy plastic green roof systems.

Green roofs are a path to food freedom for the urban core.

Green Roofs support Food Freedom, Florida Rooftop Permaculture

Issues concerning the safety, quality, availability and cost of food are important considerations today, especially as corporations and state actors try to monopolize energy, water, transportation and other needed fundamental necessities for life.

Green Roof Okra Seed Pod - Seeds - new currency

Yet as generations pass, the knowledge and secrets of agriculture and permaculture are slipping away.

Articles such as the one  found here where a Wisconsin judge ruled Americans do not have a fundamental right to keep livestock and grow food,  illustrate the fear and worry of federal judges ruling against basic food rights.

As our Urban Core becomes more and more populated and our buildings higher and taller, we the residents will need to know how to grow food across structures.

Recently, my friends Val and Eli were cited by the City of Jacksonville for growing food in their front yard.

Mark and Amanda Searle have been both cited and fined for hens in their backyard.  Others have had their egg producing pet hens taken in front of teary-eyed children.

Am I paranoid?  Maybe so.  But as corporate control and lobbyist-driven legislators becomes the norm, we should have a back up plan.

If the GMO turns out a generation of pain, or if seed and food becomes so expensive we cannot afford to feed our families, we must have an alternative.

Rooftop and windowsill permaculture provide an answer.

Net Negative Carbon Florida Green Roof

The two photographs here show how much biomass is growing on the Breaking Ground Green Roof.  The first photo was taken May 5th, 2011.  The next photo was taken October 9th, 2011.

Green Roof, May 2011, Breaking Ground Contracting

Green Roof, October 2011, Breaking Ground Contracting

We are having a biomass harvesting party later this month where we will be calculating how much dry weight plant material is harvested and the estimated sequestered carbon.

Having a green roof pull carbon from the urban core atmosphere and pump fresh oxygen into the air is one step towards restoring the health of our cities.

For more  info on the Breaking Ground Green Roof, visit the project website here.

Residential Green Roofs, Small Scale, Big Impact

Genora's Green Roof,  Jacksonville,  Florida

Genora Orth's green roof may be considered small by some.  Approximately 13' by 10' the living roof captures rain from most of the front porch portion of the historic Riverside Avondale home in Jacksonville.

Anecdotally I estimate of all stormwater flowing through and then off the entire roof, about five percent is intercepted by the living roof soil media and plants.

Individually five percent of a house's roof is not much, however collectively five percent is very significant.

On Genora's roof for example, the 130 square foot living roof over the porch captures another 200 square feet of roof run off from the area above the living roof.

Quick calculations show a two inch rainfall event across 230 square feet of roof would produce about 400 gallons of stormwater.

Normally such an amount coming off asphalt shingles would carry contaminants, not only from the petroleum based asphalt shingles but also those contaminants from the urban core atmosphere.

Jacksonville has approximately 300,000 homes and residential structures, all contributing stormwater directly or indirectly to the St. Johns River and Floridan aquifer.

If 10% of the homes in Jacksonville were to install a living roof on their front or back porch there would be a total of 30,000 homes with small green roofs.  If each green roof attenuated or cleaned 400 gallons of stormwater then the total amount of treated and cleaned runoff would exceed 1,200,000 gallons.

However, just think what would happen if just half of the residential structures in Jacksonville installed small green roofs like Genora's then over 6,000,000 gallons would be cleaned and attenuated before reaching our Floridan aquifer and St. Johns River.

Now consider the fact that it is estimated there are several million residential structures in Florida.  If each had a small green roof like Genora's living roof then close to a billion gallons of stormwater runoff could be intercepted and cleaned before reaching our waters.

Just as the tree lady of India, Janet Yegneswaran plants one tree at a time, small green roofs could cover the urban and suburban core one roof at a time.

Genora's efforts make a strong statement of sustainability, providing us with an example and a challenge to do something ourselves to help clean our rivers, streams and waterbodies.

Green roofs don't have to be big to impact the world.  Small scale green roofs carry a message of powerful intent.

Flat, Extensive Green Roof Typical Cross-Section for the Tropics and Hurricane influenced Areas

I receive daily requests for typical cross-sections so I thought I start posting some of the more popular.

The above system is our system we've tested at the University of Florida's Civil Engineering Hurricane Simulator.

If you'd like a pdf version, email me here - kevin@metroverde.com and I'll be glad to send you one.

Florida Green Roofs: Creating Communal Habitat for Wildlife in the Concrete Jungle

Nature welcomes any small patch of greenery across the otherwise barren rooftops of the urban core.  Early yesterday I was working on the Breaking Ground Contracting site - we are installing a clumping bamboo hedge between the site and I-10 and walked up to the rooftop garden area.  Two Gulf Fritillary butterflies were mating.

Green Roof Butterflies (Gulf Fritillary) Mating, Breaking Ground Contracting Green Roof

 We've all been amazed at how quickly the green roof was colonized by wildlife.  Every day brings a new species or chance to see what normally we miss.  Interestingly, the pair chose a quieter spot, back toward the original rescued ground level site plants, away from all the native wildflowers and zinnia's to share.

Green roofs are so very special to the urban core.

Green Roof Butterflies (Gulf Fritillary) Mating, Breaking Ground Contracting Green Roof

Green Roof Butterflies (Gulf Fritillary) Mating, Breaking Ground Contracting Green Roof

Green Roof Butterflies (Gulf Fritillary) Mating, Breaking Ground Contracting Green Roof