An Expensive Florida Living Wall's Death. Why?

Florida boasts several wonderful Whole Food stores and I enjoy shopping within, relishing the samples of exotically delicious cheeses, thin sliced blood oranges and store-made salsa.

After yesterday's visit I chose a chair on the marketplace's front patio, affording me an opportunity to sit and think about why their beautiful and very expensive Florida Living Wall trellis system and plantings had miserably failed.

Whole Foods' dead Florida Living Wall

The living wall failure was nothing new.  Ever since the store's construction and opening in 2008-2009 I had watched in fascination at the shiny stainless cabling and support brackets, hoping to see a lush, tropical wall of living, breathing vegetation established, one providing habitat for Florida's native anoles and tree frogs (themselves wonderful pest-management strategies), cleaning stormwater, fixing CO2, pumping fresh oxygen into the air, providing a much needed Sense of Place in an otherwise increasingly Urban Concrete Jungle and more.

However, despite the expensive trellising, cabling and other stainless attachement hardware, the wall supported little else but brown, dried and dead plants and vines.

Florida Living Walls must be designed with appropriate criteria to ensure survival

Such a shame because the trellising highlights the main entrance.  Customers must walk past the dead vines and plants to enter the store.  Though I am not a high-powered marketing expert I can easily recognize a sense of failure, brown and disappointment that most people would subconsciously acknowledge when walking past the dead vines and plants.

What went wrong?  Who did the install and design?  

Surely the trellis system was expensive enough and fabricated from a high quality material.

Why, after numerous attempts at plantings by staff and contractors are the living walls still dead?

Invasive Nandina is hiding the failed Florida Living Wall, Whole Foods, Jacksonville, Florida

These are all questions a good living wall designer must ask themselves long before final project specifications and ultimate installation.

Certainly the issue is not one of plants and constructed buildings being fundamentally unable to coexist.  As we read in yesterday's post 'Green Roof Sleuthing' shows us just how compatible plants and structures actually are and in fact, buildings would soon be overgrown with plants if left unattended.

Some landscape designers I've talked to scratch their heads, wondering why the plants they typically specify and use in horizontal landscapes just dont work in Living Wall or Green Roof applications.

And there are many very important differences.

I've always said Living Walls are magnitudes times more difficult to design and successfully keep looking good in the long term.

So the designer needs to be on his or her game up front.  All important design criteria must be analyzed and recognized when specifying all the components of a Florida Living Wall System.

As I rested on the front patio of the Whole Foods Marketplace in Jacksonville and examined the Living Wall design, the issues became obvious.  The opportunity for a magnificent Florida Living Wall, one that would greet customers with lush texture, color and scents was there.  Some of the components though were missing or ill-installed.

So what is the answer to the Whole Foods' dead Living Wall in Jacksonville?

Tomorrow's post will discuss what I perceive mut be done to produce the Florida Living Wall, one that would greet customers with lush texture, color and scents and truly welcome and invite money-spending clients inside.

Green Roof Plant Sleuthing! Understanding why some plants grow better on roofs.

I call the process - 'Green Roof Plant Sleuthing'!

Simply put, Mother Nature is the best teacher for what grows well on a wall or on a roof in hot, dry, arid and monsoon-like climates.

Nature created green roofs cool buildings and provide habitat

When students of Green Roof technology ask me for recommendations concerning plants and green roofs, the first task I suggest is always to do a little Urban Sleuthing.  Walk around downtown, watching your step and keeping an eye out for traffic yet looking up to the city roofs, gutters and tops  of building structures.

Most are amazed to see just how many plants actually grow out of cracks, with minimal soil and survive the typical harsh conditions of a rooftop.

Green Roof Sleuthing is fun & educational!

Excitingly, these naturalized plants can produce a full and flush growth habit, offering an almost tropical look to the roof.

Walking through St. Augustine the other day I ran across many nature inspired green roofs, all quite beautiful and providing habitat, cleaning stormwater, cooling the buildings and pumping fresh oxygen back into the air.

Hidden among the lush resurrection fern were also many interesting smaller ferns, vines and other plant species.

MetroVerde finds many new Green Roof Plants through Florida Green Roof Sleuthing

So next time you wonder about the type of plants to use on your next green roof project, be sure to consult with your local nurseries and growers but also do not forget to do some Green Roof sleuthing yourself.   Take a walk through the downtown and look up.

Chances are you may never use those plants you see growing out of the buildings but then again, knowledge is power, especially when working with plants on roofs!

Rain, Green Roofs in Florida and Climate Change Issues

Drought everywhere!  Jacksonville received only a small amount, way less than a tenth of an inch of rainfall last night.

MetroVerde Florida Green Roof, Breaking Ground

Here in Jacksonville we've had little if any rainfall for weeks now.  The saying spring showers brings May flowers does not hold true for the geographic climate here.  As weather fronts push down and across the US they loose momentum and dissipate just before reaching Jacksonville.  All the dry weather is rough on green roof plants.

However, being situated on the Atlantic Ocean we are constantly exposed to high winds.  When the weather fronts come through they drop all their moisture west of Jacksonville typically but retain enough wind turbulence to stress unprotected green roof plants.

Over the past year on the Breaking Ground Green Roof I have watched in amazement at the amount of water the dry winds were stealing from the plants as breezes whipped across the flat roof at 4 or 5 meters per second.  Are we seeing the results of climate change or is this an expected cycle?

Of course the CAM plants were fine and this is why we suggest planting a belt of CAM plants around unprotected green roof perimeters.  CAM plants generally keep their stomata closed during the day.

C4 plants like the Poaceae hold their own, as long as they are established.  The corn, lemon grass and native grasses don't seem to mind the desiccating winds though I am sure after time they too would suffer without some rainfall.  I love the wave action native grasses produce in the wind.

The Asteraceae too do well, again as long as they are established and again, most are considered C4 photosynthesis possessing plants.

But the C3 plants can dry out so quickly.

Because we are doing an install I water the plants to help them settle into their new home.

Typically, wind is so drying and strong I can hold the hose to where the stream of water was flowing vertically up and evaporating or being stolen by the wind before the droplets could ever make it back down to the plants.

Watching the C3 plant leaves move in the wind I could see the same occurrence happening, water being quickly vaporized out of the leaves just as the droplets from the hose where also 'gone with the wind'.

Sitting there with the hose I witnessed some of the more tender vegetables quickly wilt even with the hose  water directed at their roots.  The plants vascular system could not keep up with the wind induced evaporation of leaf moisture.

Without water in the leaves plants can not conduct photosynthesis.  Without photosynthesis plants die,

Wind impacts are so significant across green roofs.

In MetroVerde's opinion wind exposure is, with light, availability the most important consideration for green roof design.

We've posted numerous articles here on how to use CAM plants as wind breaks.  Understanding wind impacts on green roofs is critical for long term green roof design success.

Best Plants for Florida Green Roofs? There are many says MetroVerde!

Best Florida Green Roof Plant?

Metroverde is always working to find suitable plants for Green Roofs in Florida.  For years Northeast Florida has been experiencing a severe drought.  Finding the toughest and most visually appealing is only part of the process.  Habitat value, invasiveness, wind and drought tolerance are other issues we consider.

Green roofs in Florida are harsh places – remember the 7 (or more) H’s:

1. High Humidity
2. Hot, hot heat
3. High desiccating winds (killer)
4. Hurricanes (not the football team)
5. Hard Freezes
6. Horrible temperature swings
7. Hurtful droughts
8. Harmful floods

And we all are cautious about irrigating a green roof (I speak as a lawyer – not a botanist here) – our litigious society has already bred a number of legal articles on green building and tort.  Imagine – the issues of:

• Mold
• Water damage to interiors
• Collapse from weight (water is heavy)
• Bacterial breeding
• and who knows what else…

So if we choose to acknowledge Florida’s water shortage problem and build a green roof with micro-irrigation or no irrigation at all, then we need to look to plants that:

1. Can survive the many H’s
2. Are visually acceptable by the community
3. May be cost-effective
4. Are preferably native species (or non-invasive species)
5. Do not present a fire hazard or contribute too much dry leaf litter
6. Are low maintenance
7. Can survive long periods of drought
8. Can survive twenty inch downpours
9. Resist fungal infestations
10. and much more

Two of the most outstanding plants that almost begin to come close to the above requirements are:
1. Frog Fruit (Lippia nodiflora), and
2. Wild Garlic (Allium canadense)
I’ll be posting more data on these two species over the next couple days.  In the meantime – what are your experiences with these species on green roofs?

Green Roof Plant Dwarfed 2 Year Old Allium Canadense

Florida Green Roofs and Wind Impacts on Green Roof Plants

Wind is an oft-neglected but so important design parameter of green roof layout.

Dry, desiccating winds can damage or kill green roof plants faster then drought or a host of other environmental factors.

Included here are two photos of the same black-eye pea plants.  One is on a wind protected green roof, the other is on a wind exposed green roof.  Note the wind burn on the wind exposed roof plants.

Both looked the same prior to the 48 hour wind storm just leaving.

MetroVerde  recorded between 10 and 20 Km/Hr winds on a continual basis for the 48 hours with almost non-existent water vapor or air humidity.

Florida Green Roof, Wind Protected Green Roof Plants

Florida Green Roof, Wind Exposed Green Roof Plants

Wind can burn or kill green roof plants quickly, taking an otherwise beautiful planting and turning into a brown mess within a matter of days.  Even with more than adequate irrigation water applied - simply because the vascular system of the plants cannot keep up with the demand for water in the leaves.

CAM plants and those plants with stomata remaining closed or closing under lack of water conditions must be used as perimeter wind break plants on green roofs with out parapets or other wind protection if the green roof is not otherwise sheltered.

Understand the different types of photosynthesis green roof plants have.  For a primer, check out the many articles we have posted before on CAM, C4 and C3 plants.

Other helpful sites are included here;

Great Irish Gardening blog article on wind damage in Ireland to garden plants.

North Carolina State University has another brief yet informative note on wind desiccation of plants.

Very interesting and informative Permaculture Wind Break Site.

Remember, your green roof site may receive plenty or precipitation or irrigation water, but if it is constantly exposed to desiccating winds the plants will experience the effects of wind damage.

Florida Green Roofs and a Terrible Drought! Looking to Poaceae

Here in Northeast Florida we continue to suffer from extreme drought.  Strange, because four hundred miles west lies the city of Pensacola with an abundance of rain.  But here in Jacksonville, a harsh, dry, period of time marked with a significant lack of water is stressing and killing plants and contributing to wildfires.

Selecting those native plant species adapted to drought survival is important for green roof designers.

Poaceae is a good place to start.

Poaceae is the family of grasses, referred to previously as Graminaceae.  According to Wikipedia, Poaceae contains about 600 genera and around 10,000 species of grasses.

Grasses comprise from 20-25% of all the herbaceous vegetation covering the earth.

Wikipedia, as other sources also suggest the Poaceae is the single most economically important family of plants in the world to humans, containing many food, grain and cereal crops, such as corn, rice, wheat and barley.

Poaceae grasses contain both C3 grasses and C4 grasses, referring to the much discussed in this blog 'photosynthesis process' type.  The above link also contains a list of commonly known C4 plants.

C4 plants have evolved a process to survive drought.  They protect compounds in their leaves, crucial to photosynthesis, from dessiccation and loss through a variety of means, including; timed stomata openings, storage of photosynthesis compounds in vacuoles and separation of photosynthesis reactions into differentiated cells.

This means they can make an excellent green roof plant or rooftop garden species.

As does corn.

Corn growing on Rooftop Garden, Sudan, photo by S. Newman

Sudan is dry.  Corn, Periwinkle and Mango thrive. Photo by S. Newman.

As you can see from the above photos, Sudan is a dry and arid place, hostile to most plants.

However corn, a Poaceae family member thrives on a hot, dry, windy roof.

MetroVerde also grows corn on roofs, and the plants will grow well in places most others would wilt in a matter of days.

Other grasses too, members of the Poaceae family adapted to drought make excellent green roof plants.  many are perennial and evergreen species, affording year in and year out color and texture, supporting biodiversity with food and communal shelter, providing beauty, cleaning stormwater and reducing heat island effect.

Purple muhly grass, Muhlenbergia capillaris, is another of my favorite green roof Poaceae.

Green Roof Muhly Grass, photo by C. Burkee.

Purple muhly gras, excellent C4 green roof grass.

There are many other grasses available and suitable for green roofs.  Preferring to use native species, I consult with local nurseries in an area to see what they recommend for drought tolerance.

Your local native plant society is also a good resource for grasses recommendations.

The beauty of the Poaceae family is that they have been around a long time on this earth and survive in the most inhospitable of places.

Try Poaceae on your next green roof!

Green Roofs, Deciduous, Dormancy and the Color Brown

Though not my favorite time of the year Winter always brings the welcomed sigh of relief to her pallet of colors with the appearance of a special deep brown.   Anticipating next year's vigorous renewal,  brown adds the fourth dimensional depth of time to the remaining sprays of green.

MetroVerde Green Roof Panel

Winter on the green roof is no different.  In fact, winter on the green roof allows for a period of correction, recollection and hope.

Of course Winter here in Florida is mild compared to what others across the world experience with respect to duration, we still get cold enough here to induce dormancy and deciduous characteristics in   many plant species (If you call a low seasonal temperature of the mid-20's F or - 6.5C cold).

Aptenia on a MetroVerde green roof

While it is always good to look out across a living roof and see vast expanses of green, deciduous brown can be reassuring.

Without the annual browning of the fast growing C3 plants the living roof would become a jungle, restricted in biomass output only by available water supply.  However after the first hard freeze, dead biomass can be removed from the living roof to expose C4 and CAM plant type successes, successes to be built upon for subsequent years design and growth planning.

C3 and CAM plants across a sloped green roof in Florida

For living roofs in dry and arid climates experiencing sub-freeeaing winter temperatures, winter visualness can be designed to allow for striking contrast of textures and colors.

Catherine Burkee, Educational Director for Breaking Ground Contracting here in Jacksonville has a wonderful video and note of the Breaking Ground Green Roof she recently posted about the changes of seasons as seen on their living roof.

I am looking forward to a great 2012 for living roofs around the world!

Nature Designed Florida Green Wall & Living Roof Photos for Monday, December 12, 2011

Enjoy these Monday Morning Volumetric Green, Living Walls & Green Roof Photos - most nature designed!

Volumetric Green, downtown St. Augustine

Volumetric Green, downtown St. Augustine

Look closely and you can identify many different plant species

St. Augustine, Florida Resurrection Fern

St. Augustine, Florida Resurrection Fern

Resurrection Fern on the Roof

Resurrection Fern on the Roof

Living Wall, St. Augustine, Florida

Legumes atop a St. Augustine Stone Wall

Feral Sedum in the Rain Gutter

Florida Green Roof Allium

Aloe on the @BGGreen Roof

Bignonia Walls at the Jacksonville Zoo and Gardens

Green Roof and Leaves, Cation Exchange and Anti-Allelopathy Issues for Design Consideration

I had a couple of comments yesterday about my post on Allelopathy and Green Roof design.  As we focused on the potential negative impacts adjacent trees and their sap drip, leaves, seeds and shade can have on green roof plants we should also remember certain trees can bring distinct advantages to a green roof or nearby permaculture garden.

Leaves on the Green Roof can exert both Allelopathic and/or anti-Allelopathic influences

One comment suggested we should take into account the addition of organic matter from leaves, replacing lost or broken down compost.


Trees or adjacent shrubs that stimulate growth through their presence, leaf or sap drop or other factors are commonly referred to as possessing 'Anti-Allelopathic' properties.  An anti-allelopath encourages nearby plant growth.  Actually this is a big complicated name describing a common simple practice - composting.


Chinese tallow tree, Triadica sebifera, a terribly invasive species here in Florida and across tropical areas is rated as one of the best anti-Allelopaths, her leaves and sap encouraging adjacent plants to grow as though fertilizer has just been aded to their base.


Leaves can be very useful on the rooftop garden, green roof or in the ground level permaculture garden!  Leaves cool the soil, promote soil moisture content, provide organic matter (good for bacterial breakdown of pollutants) and supply micronutrients, can adjust  pH and cation exchange potential.


No leaves?  May not be too glamorous yet very practical ( remember Louis Sullivan and functionalist architecture) collecting your neighbor's bagged up yard leaves can benefit your green roof or permaculture garden and benefit your wallet.


As mentioned, cation exchange capacity and pH are two important variables of a green roof. Additionally, leaf compost can add valuable trace minerals needed by the rooftop plants.  Some trees, including certain maples containing high sugar content in their sap and leaves possess an extremely low pH, in the range of approximately 4.5 to 5.5.  Other leaves such as white ash and popular may have quite high pH's, approaching 8.0 or above.

American sycamore leaves shown here can exert Allelopathic influences

Leaf compost typically contains twice the amount of trace minerals by weight as does horse manure.  


Interestingly, leaves from different species of trees offer varying characteristics. While ash leaves are relative neutral in pH, some maple species leaves are documented to possess a pH of around 4.5. 


Research also shows use of properly composted leaves greatly increases the cation exchange capacity of soils. One of the important functions needed in green roof soil media is cation exchange capacity.


Though varying opinions of organic compost value to green roofs exist throughout the industry, many believe organic material in the soil media is highly beneficial to green roof plants.


Massachusetts' state DEP has published an informative paper on the value of leaves for compost, including discussing issues and benefits, nitrogen to carbon ratios, composting processes and more.  This information is helpful to those just starting composting or those interested in studying potential allelopathic or anti-allelopathic effects on their green roof, living wall or ground level permaculture bed.


Fossa alterna technology also relies heavily on leaf use and in turn has produced informative leaf nutrient information.

Remember, green roofs are individual ecosystems, intricate webs of life with complex interactions.

Flat roofs with poor drainage may or may not require lower organic content to prevent water saturation and facilitate drainage.

Sloped roofs may function appropriately with high organic content.

Again, if you lack adjacent anti-allelopathic trees then go out about the cityand find leaf waste destined for the landfill.  Collecting heavy duty garbage bags filled with fresh raked leaves (we avoid those lawns heavily treated with fertilizers and herbicides/pesticides - those lawns are easy to spot here in the US due to the small advertising signs the lawn companies stick in the lawn after a fertilizer application - and speaking of lawns and fertilizers - a short must-see video of the history of the American Lawn will have you rolling in your chair and scratching your head at the same time can be viewed here) is a positive step for the environment.

Other benefits include;

• Free highly effective cation exchange capacity supplements from the leaf compost
• Free organic matter from the leaf compost
• Free trace minerals from the leaf compost
• Free pH adjustment material from the leaf compost (this is especially important when using higher pH soil media or media high in calcium)
• Free garbage bags
• And a lesson to your children riding with you to scavenge that recycling is more important than pride. :)

Green Roof Photos for a Florida Thanksgiving

Happy Thanksgiving ya'll from the hot & dry deep south.  Enjoy the fresh, just snapped Green Roof photos!  Blessings to all.

Rooftop Permaculture - Fresh, Dew Kissed Greens on the Green Roof by MetroVerde

Pink Muhly still blooming in late November on the Green Roof by MetroVerde 

Mint, Basil, Garlic & Clover on the MetroVerde GreenRoof 

Autumns leaves decorate the MetroVerde Green Roof

MetroVerde  Green Roof Lemongrass & Salad Greens

MetroVerde Green Roofs are shallow and lightweight

Living Roof on the front porch of a home in the Riverside Avondale Historic Preservation District

MetroVerde's green roofs are nature irrigated and use many native wildflowers

Mint and Allium on the MetroVerde Green Roof

Green Roof Plant Design - Useful and Harmful Effects of Allelopathy

Plant matter such as bark, leaves, twigs, nuts and pollen can act as a herbicide, interfering with other plant's cell division, nutrient uptake, photosynthesis, et al.   Some plants have strong effects on other plants, preventing growth in some and encouraging growth in others.

American Sycamore leaves are known for allelopathic properties (maybe they will surpress the Bidens alba!)

The University of Florida defines allelopathy as, "beneficial or harmful effects of one plant on another plant, both crop and weed species, by the release of chemicals from plant parts by leaching, root exudation, volatilization, residue decomposition and other processes in both natural and agricultural systems."


Plant matter such as bark, leaves, twigs, nuts and pollen can act as a herbicide, interfering with other plant's cell division, nutrient uptake, photosynthesis, et al.


An allelopathic tree usually exerts  negative influence on adjacent vegetaion via a number of different processes, including;

• Fog & dew drip
• Leaf litter
• Volatilization 
• Sap drip
• Pollen
• Other biological processes

Understanding allelopathy is especially important for green roofs and rooftop gardens with surrounding, adjacent taller trees.  Allelopathy can greatly surpress rooftop food production.

According to the University of Georgia, School of Forestry Resources , there are a number of significant allelopathic trees requiring attention when planting other plants nearby.  They include;

Strong Potential for Allelopathic Impacts 
Acacia spp
Acer saccharum
Ailanthus altissima
Celtis laevigata
Celtis occidentalis
Eucalyptus camaldulensis
Eucalyptus globulus
Eucalyptus spp 
Juglans cinerea
Juglans nigra
Leucaena spp
Myrica cerifera
Picea engelmannii
Platanus occidentalis 
Populus deltoides
Prosopis juliflora
Prunus cornuta
Prunus serotina leaf 
Quercus falcata leaf 
Quercus marilandica
Quercus rubra
Quercus stellata
Robinia pseudoacacia
Sassafras albidum
Ulmus americana

Moderate Potential for Allelopathic Impacts
Abies amabilis
Abies balsamea
Abies grandis
Acer circinatum
Acer negundo
Acer platanoides
Acer pseudoplatanus
Acer saccharinum
Aesculus glabra
Aesculus hippocastanum
Aesculus octandra
Arbutus menziesii
Carya illinoensis
Carya ovate
Corylus spp
Crataegus spp
Fraxinus excelsior
Ginkgo biloba
Gleditsia triacanthos
Juniperus monosperma
Juniperus scopulorum
Kalmia spp
Picea spp
Pinus banksiana
Pinus contorta
Pinus densiflora
Pinus edulis
Pinus elliotii
Pinus monophylla
Pinus ponderosa
Pinus sylvestris
Prunus pumila
Quercus alba
Quercus borealis
Quercus douglasii
Quercus gambelii
Quercus michauxii
Quercus shumardii
Rhododendron maximum
Rhus copallina 
Sorbus sitchensis
Tsuga canadensi

Slight Potential for Allelopathic Impacts
Abies concolor
Aesculus spp
Betula pendula
Carpinus spp
Casuarina spp
Cupressus macrocarpa
Fagus spp
Fraxinus spp
Larix decidua
Picea excelso
Pinus palustris
Pinus spp
Populus spp
Pseudotsuga menziesii
Quercus petraea
Quercus robur
Quercus rubra
Salix pellita
Sambucus racemosa
Sequoia sempervirens
Taxus brevifolia
Thuja plicata
Tilia americana
Tilia cordata
Tilia planifolia
Ulmus laevis
Ulmus parvifolia
Umbellularia californica

Adjacent to the Breaking Ground Green Roof (see photo above) there are American Sycamores,  Platanus occidentalis located in the southeastern and southwestern corners of the living roof.  The American Sycamore can produce significant allelopathic influence on adjacent green roof plants.  Data exists showing the active ingredients, scopoletin and chlorogenic acid found in the Sycamore leaf may    interfere with the ability of stomata on certain plant's leaves to function.

Interestingly, according to the University of Florida's IFAS publication referenced above, allelopathic properties can also be used strategically to control certain weeds, i.e. dried mango leaves surpress nutsedge tubers from sprouting.

Finally, good green roof design incorporates into design the potential and foreseeable effects of adjacent trees and other vegetation.  Recognizing and dealing with a potential allelopathic problems during design can save months or years of not knowing why a green roof is barely surviving.

Know the basics of plant allelopathy is you intend to work in green roof design!

Fertilizing Green Roofs? Stop Now!

Did you know your industrial fertilizers you are spreading across your rooftop garden contain Persistent Organic Pollutants (POPs)?  Or are we denying the many silent environmental and health impacts of POPs.

Having read the article posted by @psustentavel on Twitter - click here for the article about Persistent Organic Pollutants - the imagery of 'inorganic chemical 'fertilizers across countless green roofs,  the use of drinking water for irrigation - even backup irrigation - and the reckless abandon with which we use non-native species for landscapes, including those on rooftops, made me think - in our rush to install green roofs atop buildings, are we too creating a chronic issue someone else will have to pay for?

The value of green roofs is unquestionable.  There is solid scientific data to back up claimed benefits of habitat creation, carbon sequestration, oxygen production. greenhouse gas reduction, heat island effect tempering, cleaning of stormwater, integrated pest management and so much more.

Florida Extensive Green Roof Nature Irrigated

There is no doubt about the value properly designed and maintained green roofs can bring to the Urban Core.

Green roofs can be used to support Urban Permaculture - small scale, individualized rooftop farming operations providing food, fiber and medicine to city residents.

And many urban areas around the world are moving ahead with plans to increase urban agriculture.  Singapore, for example, produces 25% of the entire city's vegetable crop within the city limits. For a fascinating look at the importance of urban permaculture  read foodsecurity.org's white paper entitled Urban Agriculture and Community Food Security in the United States; Farming From the City Center to the Urban Fringe.


Rooftops are the new frontier of real estate in many urban areas.  Cities with limited available ground level real estate have acres of open rooftops.

Vegetated and green roofs are increasing in popularity, showing an impressive growth rate trend over the past decade.  According to Greenroofs.com, public awareness of and interest in green roofs is steadily growing.

Yet in our noble rush to restore volumetric green to the urban core we hopefully will recognize the potential environmental costs associated with mass production of green roofs.  The 'One Size Fits All' approach to green rooftops will not work for the worlds vastly different ecosystems.  Sadly and reminiscent of mega-agriculture's damaging past practices, we as an industry turn to potent chemicals to fertilize, control pests and then use much needed drinking water to either irrigate or serve as backup irrigation.

Independent and craftsman-like green roof design and construction could disappear.

As with the POPs causing health issues in Pakistan and other places, our indiscriminate use of hardy invasive species, potentially toxic chemical fertilizers, pesticides and herbicides on green roofs is a Ponzi Scheme our children too will pay for.

Importantly, we as an industry have already moved far in the direction of ecologically inappropriate and environmentally dangerous green roof design.  Florida's FDEP green roof in Pensacola, Florida possesses a large drip irrigation system, backed up with potable drinking water and planted with slow-release fertilizer compounds and soil amendments.

As in hidden environmental consequences associated with corporate profitability, denial of reality is the basis of success.  Though the 'green' benefits of the FDEP green roof are often touted in the media - the fact that chemical fertilizers are applied and potentially damaging to Escambia Bay's ecosystem are hidden.

Yet FDEP is fully aware of the environmental problems resulting from POPs, fertilization and pesticide use on green roofs.  In the proposed, new State of Florida Stormwater Applicant's Handbook,   FDEP allows green roof credit for volume retention of stormwater only (no water quality credit),  and recognizes fertilizers and pesticides will be used on green roofs (why no water quality credit is given), an approach we must reject.  Moreover, FDEP is requiring the purchase and use of a 'pollution control media' made from ground up automobile tires under the green roof soil media to keep the fertilizer's nutrients on the roof.

Over time and as water evaporates, added pesticides, herbicides and fertilizers will concentrate back into the surface waters and become an issue for our children.

In the rush to add volumetric green to the Urban Core, the POP issue could easily go unnoticed.

Temper the hurry to install a green roof with the knowledge of a local native species botanist and a soils expert.  Rather than ordering large amounts of hothouse pampered plant material, find a local nursery with individual plants acclimated to the climate.

Green roofs can be crafted to add artistic, educational, ecological and ethnobotanical value.

But we must first reject the incorrect notion that green roofs must be fertilized, irrigated with drinking water and doused in pesticides.