Wednesday, April 30, 2014

Green Roof Roof Drains Reference Links

Sizing Roof Drains for Green Roofs (and All Roofs In Fact) is Important
I spent a good hour last night worrying about a new green roof we are working on, and how it would drain with the roof drains designed by the project architect.

Right away I will say that I am not qualified to design roof drains.  Sizing roof drainage is a function for a qualified architect or engineer, not a green roof plant person.  However, I still worry.

Living in Florida I have seen some heavy and prolonged downpours.  Last night in fact, across the panhandle area of western Florida, rainfall totals reached almost 24".  That is a lot of water to move off the roof.

Of course storms dumping huge quantities of water do not happen every day.  But I still want my green roofs to drain.  Most green roof plants do not like 'wet feet' so to speak and I certainly do not want the green roof plants to float off the roof.

Yes, I ultimately trust most architects and engineers on their designs for they are accomplished professionals.  But for those occasions, like last night I feel better after a second opinion.

Now I am not vouching for their accuracy, but there are several easy to use Roof Drain Sizing calculators published across the internet.  It only takes a few seconds once you have the approximate square footage of the roof you are wondering about to see just how many roof drains are needed for different areas of the country.

Do not use these for design, but like last night, when I was wondering if the architect got the design right, these sites may be a good second opinion.

So stop worrying and check out some of these Roofing Drain Sizing Calculators:


Sunday, April 27, 2014

Tropical Storm Season is Here, Is Your Green Roof Ready?

It is that time of year again.  Soon there may be cyclones in the Atlantic, wave after tropical wave forming off the African continent and storming westward across the Atlantic.

If your green roof has a parapet then you are lucky.  Most testing has shown parapets minimize wind damage to a green roof - though in a large hurricane, all bets are off.

Even if your green roof does not have a parapet it can still be designed to minimize tropical storm wind damage.

The video here is of a small green roof in Jacksonville, Florida on August 25th, 2008 when Tropical Storm Fay pummeled the northeast Florida area with over twenty inches of rain.  The video shows how the roof reacted to gusts up to 50 mph.  Wind speed was recorded using an ExTech anemometer.

The roof shown in the video does not have a parapet and is sloped.  The video illustrates how the irregular surface of he vegetated roof interrupts wind generated uplift that can damage asphalt shingle roofs.  The plants range in height from two inches to six inches and can be seen moving back and forth in response to the wind.



Wind racing across a flat surface can create lift - or a vacuum - and literally lift the shingles or roll roofing up off the decking below.

The plant habit acts to break the shear flow of air, creating turbulence and working against damaging uplift.  Planting more wind tolerant plants, such as some succulents or grasses may actually create wind breaks in a manner similar to the way a parapet would act.

Another important quality of a well designed green roof is the drainage factor.  The roof here is allowing a rapid drain of roughly 18" of rain over a 24 hour period without washing out. 

Monolithic hurricane mats used as the basis of the planting system allow for quick drainage of the stormwater and create a mechanism where plant roots can attached and anchor themselves to the roof all the while holding soil in place.  A well established root architecture  is important  for tropical green roofs subject to high winds and heavy downpours.

We will always deal with the 5 H's here in Florida - High Heat, High Humidity, Hard Frosts, Hurricanes and Hard Desiccating Winds, but with good green roof design your Florida Green Roof can hopefully withstand a severe storm, including tropical storms!

In the meantime, there are some precautions the green roof owner can take to prepare for tropical storm season (May 15th for the Pacific area and June 1 for the Atlantic regions).

At a minimum, we recommend;
  1. No large trees on a roof.
    1. Small shrubs and small trees may be used successfully depending upon the final design.  This may seem like a common-sense guideline but people try to put all types of tall, large trees on patio or garden roofs.  During a 130 mph cyclone, the tree may be blown over and may cause damage from the fall against the structure or to the street below.  It may also become airborne if the winds are strong enough.  Growing up in Hialeah I saw plenty of hurricanes come through our area and witnessed first hand the power of these storm events.
  2. Anything and everything on a roof should be permanently attached.  
    1. Walkways should be constructed from a permanently attached TPO, EDPM or other mat and permanently affixed to the roof.
    2. No loose chairs, tables or other items should be present.  If you wish to have a chair and table stay on a roof during a cyclone, they must be permanently attached.
    3. All green roof components must be permanently attached to the structure.
    4. Any trays, plastics, pots, containers or other green roof components must be permanently attached to the building structure.  Florida Building Code does not allow for loose items to be installed on a roof - they must be attached.
    5. Green Roof Irrigation components must be permanently attached to the roof.
  3. Make sure all tools and gardening utensils are picked up and put away.
    1. It is very easy to forget the pair of shears, scissors or pliers on a roof.  Remember what you were using and where you liad them.
  4. Plant selection should be focused on those species that have historically survived cyclone and hurricane incidents.  There are several good books available at most bookstores here in Florida on proper cyclone resistent landscaping and many resources on the web, such as the Brevard County Landscaping Guide for Hurricane Areas.
  5. Check on the NOAA National Hurricane Center website daily.  The NHC webpage is a wonderful resource, full of links to climatic data.
Always use a green roof design or green roof system already proven in actual field trials with hurricane simulation testing.  Watching a green roof blow off during a storm is an avoidable event.  Due diligence upfront and preparedness is important for green roofs in hurricane prone and cyclone impacted areas.

Monday, April 21, 2014

Green Roof Videos

Sometimes I can't sleep at night.  My titanium aortic valve makes a racket at night and the Dacron aorta feels like an overfilled balloon bouncing around in my chest.  Times like these I want to watch #GreenRoof videos!  So I made my own collection of my favorite green roof videos and now it is easy to watch them over and over.

Here is one of my favorites:

https://www.youtube.com/watch?v=cbzOUC0UICo

I can learn from the pros, like Dusty Gedge and others.  I can also watch others and learn what not to do - like stand on a roof without rails and risk falling off to certain broken somethings or worse.

I am amazed at just how many greenroom websites include photos of obvious OSHA violations where staff are leaning over the edge of rooftops high in the air without personal fall protection equipment.  Safety First on Green Roofs!

Anyway, I hope you enjoy these videos and also do not fall off your green roof! I will be adding more and changing out other videos on a frequent basis.  Please email me links to your favorite green roof or living wall videos and I will try and include those too and give you credit for the link or video if you wish - send the links and comments here.

Sunday, April 20, 2014

Beat Your Florida Green Roof Wind Impacts With Rich Coastal Biodiversity

The very best way to understand how your coastal green roof (and for that matter any green roof) will preform is to visit the site as often as possible before the plants are installed.


I always say 'wind is the biggest killer of green roof plants' and there have been many posts about wind impacts in this blog over the years, including;

Wind and light are two of the most important green roof design variables.  We at MetroVerde consider light and wind to be the two primary green roof design variables to take into consideration when developing ideas for a green roof.

The very best way to know whether or not wind is going to impact your project is to walk the site as often as possible, in the morning and throughout the day and in the evening.   Wind impacts fluctuate depending on a number of factors, including time of day.

Sunlight, air temperature and gradients and many other variables can influence air movement.

My teen daughter and I took a walk along the Atlantic coastal beach this morning and the and was blowing!  The pier's flag was standing straight out and whipping back and forth and we estimated the sped to be about 15 meter's per second - almost 35 miles per hour.

Most any plants are going to suffer in winds that fast and many broad leaf plants will quickly desiccate out and possibly die, especially as salt deposition from the ocean spray coats the leaves, stems and flowers.

Over the years we have worked on developing a green roof model that identifies those plant families with good wind resistance.

A wind resistant plant will possess either light-time activated or embedded spatial separation and protection mechanisms for Calvin Cycle processes.

Parapets are always preferred as wind breaks but architects sometimes develop client-directed roof plans with little or no parapets.  In those cases we must use wind resistant plants to serve as living parapets or wind breaks to the inner green roof.

Thank goodness there are many plants that can survive the vicious onslaught presented by salt spray and winds though.
Florida Green Roofs, coastal dunes are rich in biodiversity with wind and salt tolerant plants perfect for #GreenRoofs

Which ones?

The very best was to know whether or not wind is going to impact your green roof project and to find out what plants can survive these blistering winds is to regularly walk the project site.  

At first glance the coastal beaches may seem to just be 'green' with sand spurs. Ha!  Closer looks will show just how complex plant biodiversity on the beach dune actually is.  There are many, many species adapted to those wicked, punishing salty winds.

The very best was to know whether or not wind is going to impact your green roof project and to find out what plants can survive these blistering winds is to regularly walk the project site. 

Time to go for a walk.


Friday, April 18, 2014

How Florida Green Roofs are Born - an Idea and a Sketch

Where does one start on a green roof project?  For me it is with an idea then a rough sketch.
Florida Green Roof ideas start with a client's idea, then to a sketch. Great projects start with a simple idea.
 Many times the first sketch creates more ideas and those thoughts open more doors to expanded imagination.

Sometimes the idea may be shelved, but I suspect never forgotten.  Once an idea is created the concept has been released to the universe and could be around for a very long time.

Fabulous art deco building in the planning process for rehabilitation.
This building will be a health food, yoga and coffee shop in the near future.  The owner desires to incorporate vertical green.  We start with an idea and a sketch.

Some of the first issues we discuss include:

  • Structural capabilities (the roof is reinforced concrete)
  • City permitting requirements for landscape and stormwater
  • Wind exposure
  • Sun intensity
  • Budget
  • Maintenance
  • Theme
  • Adjoining buildings, and
  • so much more
But all journeys start with an idea.  Like a seed, the first thought grows and begins to take root.  Soon new forms appear.  Over time the creation matures, one step at a time, beginning with an idea.

My advice to all green roof and living wall designers is, "dream and let ideas flow".

Tuesday, April 15, 2014

Plant Size Considerations for Green Roofs - Size and Weight Are Important!

Sometimes we may be inclined to add small succulents to a green roof planting scheme because we know they may be tolerant to just about every environmental factor encountered on a roof.
Agave are drought, salt, wind, heat and hurricane tolerant, but they will add weight to a green roof!
Succulents can be deceiving with respect to size and weight, especially to those who have not worked long term with these plants and seen their size at maturity.  What may be a tiny, perfectly sized immature succulent may turn into a very large and heavy specimen with age.
Potential Florida Green Roof plant or potential roof problem?
Root architecture too is another important consideration for the green roof designer to take into account.

Some succulent plants develop swollen root tubers for water and nutrient storage.  Additional water means heavier weight.  Moreover, some of these roots grow in a very aggressive fashion and can damage an underlying single ply membrane or asphalt shingle roof.
Potential green roof plants have also have aggressive root systems that can damage single ply or shingles
While some small succulents, like sedum may never grow six feet tall, others can.  Though the succulents and cacti you plant may do wonderfully for the first several years,  over time they may outgrow the roof's planting bed.

Problems arise when these overgrown plants present weight issues with respect to the loading capabilities of a supporting roof structure.  An extensive green roof with smaller plants may weight twenty to thirty pounds per square foot or 100 - 150 kg/sm.  The same extensive green roof with 5' to 6' agaves may weigh three or four times the original weight.

Wind resistant can be another important factor with large plants on a rooftop, especially in hurricane impacted areas.

When you increase a roof's live load fourfold you may cause structural failure issues.

Treat some succulents as potential large shrubs or small trees.  Remember, just because a small succulent looks just right for your green roof doesn't mean it will stay that way.


Monday, April 14, 2014

Green Roofs Can Cool Cities, Learning From an Endurocap

Green roofs really do cool buildings through plant transpiration and I proved this yesterday to myself by example with an inexpensive but highly effective cap called the Mission Enduracool cap.
My Mission Enduracool cap teaches me about green roof cooling effects.
Green roofs and Mission Endurocool cool based upon the same principal as air conditioners  - that of heat being absorbed into a liquid and the liquid transitioning from a liquid state to a gaseous state.

On green roofs and across my cooling cap the liquid is water.  Plants transpire water out of their stomata during the photosynthesis processes and I sweat water and salts.  Air conditioners usually evaporate a refrigerant like freon, but all there cooling processes are based around heat being absorbed into a liquid and the resulting gaseous phase that takes place with heat adsorption.

According to the US Geological Service (USGS) about ten percent of the humidity in the air is due to plant's transpiration.  That is a lot of water!

So because I cycle most everywhere I go, my head (just like a building's rooftop) gets hot from both metabolism and from solar gain.  I always wear a helmet but that piece of safety equipment does not do much to cool except provide a bit of filtered shade.

We have talked of green roofs and their insulation value before, several times in this blog, but cooling offers additional benefits over insulation.  Cooling actually removes heat whereas insulation just blocks heat.

My first bicycle trip out with the cooling cap was to Publix, our local grocery store.  Per the cap's instruction sheet, I soaked it  in water and proceeded to wring most of the water out, leaving the cloth slightly damp.  Snapping it over my bald head I took off down the road after turning my bike's safety lights on.  The cooling effect was immediately noticeable and amazing!

Green roof plants and their transpiration right away popped into my mind.  "Hey!  This is what is happening to a building with a green roof as plants loose water to the atmosphere through evaporation", I told myself.

There are many web resources pointing out the benefits of green roofs, and their cooling potential for the urban core.

For me the maxim, 'seeing is believing' rings so true.  I learn mostly from experience.  The cooling cap taught me yesterday about the power of plants on a roof and cooling the cities.

Riding my bike I felt as if I had an air conditioner in my cycle helmet.

Sometimes short, simple life experiences can teach us more than an entire college course.  Green roofs can cool cities, I knew this before but I am so much more convinced now.

Friday, April 11, 2014

Green Roof Soil Media Questions for an Ocean Front Green Roof

I have been asking myself a question over and over again lately.  How do I keep green roof soil media from blowing off a three story, ocean front residential green roof?

The Atlantic Ocean shore - great place to learn of #Greenroof plants and to build a green roof too!
I think I have the answer but I still am asking myself the question over and over.  Not because I have doubts necessarily, but because I want to examine the issue on a regular basis, over an extended period of time.

In the past I've had new insights arise when I regularly revisit a challenge.  Challenges, be they green roof related or otherwise, are usually solved if one puts enough thought into resolving the issue at hand.

This particular green roof project will be a challenge.  Weight will be a factor as it always is.  Light will be intense and strong, all day long with no shade available.  Salt spray will be constantly coating the plants.  Hurricanes are very likely as the house sits right in the middle of hurricane alley.

But I am as confident as any experienced green roof designer can be that all these variables will  be addressed in a manner that will minimize risk to the structure, plants and surrounding area.

The daily wind factor keeps coming back into my mind though.

Any green roof will have the potential to experience much higher wind loadings.  A green roof on the ocean front usually has much higher velocity daily winds whipping across the soil and plants.  Keeping the plants alive and free from desiccation is one issue and keeping the soil media from sand-blasting a neighbor's house is another design goal (as well as simply keeping the soil media on the roof).

Ocean lots are a challenge to the #GreenRoof designer for many reasons
Sand has it's advantages and disadvantages.  Coastal dune plants, those species that will survive on a roof such as this love beach sand.  But sand has a tendency to be blown around easily and is quite heavy.  The sand here is primarily a lovely brown hue and composed mainly of crushed coquina shell, full of calcium and other trace minerals.  It drains well and holds an adequate amount of moisture.

But I am not thinking sharp beach sand would be good on the roof.  With average daily wind velocities from 5-6 meters per second up to 10 MPS and higher, I am concerned beach sand would be blown away in a matter of days, if not hours.

Walking the beach not only relaxes but teaches much.  I see things on my frequent seashore strolls that remind me of how Mother Nature behaves.  She behaves as she wants too, with little to no regard for us humans and our designs.

Mother Nature and wind has a mind of their own with regards to sand deposition #greenroofs
I view seawalls constructed with many thousands of dollars intended to hold sand in one place or keep sand out of another place and despite our best efforts these structures ultimately always loose the battle. Mother Nature puts sand where her wind blows and in other places too.

Perhaps a larger diameter, lightweight inorganic substance like expanded clay may be better.  We will analyze this in future posts.  A mature, developed green roof plant root system will go a long ways towards holding soil media in place, but can take a couple years or more to for the roots to develop and I don't want the clay to come off the roof and act like shotgun pellets in a tropical storm, damaging adjacent fenestration as ICC notes warn against.

Ultimately, root architecture may be the answer.  Comprehensive root coverage can hold soil media, plants and the green roof system in place even under storm conditions.

Agar-based tackifiers and netting have been used to prevent wind scouring of green roof soil media.  On the ocean front site I am concerned the tackifier would quickly degrade under the intense solar heat and constant salty mist.  Last thing I want to see too, is wind netting loosely flopping about after becoming slightly dislodged, perhaps beating the plants down in the breezes.

Sustainability too and green building programs call for use of local materials and are other considerations to take into account.  Sometimes local material compounding is practical or even the only way to acquire soil media.  Other times local materials may not be suitable for green roof soil applications.

Ocean front #Greenroofs face salt, wind, sun, storms and other harsh impacts
We don't want the soil media to be too dark because of high solar gain.  I spoke with someone yesterday who told me about a free roof that would not grow plants because the expanded shale was so hot he could feel the intense heat through his shoes.

We want the soil media to have a proper, plant friendly pH to encourage good plant growth too, and it needs to be primarily an inorganic mix also.

There are also many standards and reference materials to consult.

European FLL have been the most looked to standards for specification and design.

There is a simple but good short description of the green roof soil media question published by Design Cost Data here.

One of the most comprehensive and helpful discussions of green roof soil media is located on the industry website, Greenroofs.com .  The article discusses green roof soil media ASTM standards and provides links to other valuable soil media references, especially to an article by Chuck Friedrich entitled 'Don't Call it Dirt!'.

I've got a lot to consider concerning this ocean front structure's windy green roof.

Wednesday, April 9, 2014

Green Roof and Living Wall Soil Media - Vertical Green Begins Below Ground

Vines provide great vertical screening and greening capabilities, especially here in Florida where strong desiccating winds can quickly overwhelm and dessicate a planted exterior living wall,
Coral honeysuckle, Lonicera sempervirens offers interesting color and texture as a living wall
 (unless one uses a non-native invasive species like Boston Fern, Nephrolepis cordifolia, which is never recommended).

One of the most important aspects of creating a beautiful, thick and lush living wall is sometimes never even considered, that being the quality and characteristics of the soil in which the vines are planted.

Unfortunately, many designers only consider the flowers or foliage, forgetting the roots though not seen, are so critical to leaf and flower development.
Native Carolina jessamine, Gelsemium sempervirens should be nice and thick but is planted in bad soil
In urban development projects the soil can be concrete rubble with a high pH.  In situations like these a beautiful stainless and expensive trellis and nice, hot house grown plants can end up looking terrible in a matter or weeks.
Coral honeysuckle planted in poor soils looks terrible
I've written about the Jacksonville Whole Foods living wall trellis system before - an expensive living wall system that looks pitiful, all due to high pH and other soil problems.  Soil pH is a measure of acidity or alkalinity in the dirt.
Living wall vines can become woody without proper soil, loosing their leaves
The health food grocer has a high-quality stainless trellis system installed near the front entrance and on the south side of the store building.  Yet the plants have not successfully established themselves and grown well.  The store has been open now for several years, allowing plenty of time for the plants to send down roots and add  upper biomass.

The present store facility was originally constructed where another building had been demolished.  It appears some of the original slab was reused, and significant amounts of concrete, crushed block and other previous building material was integrated into the soil during site preparation.

Most plants prefer a soil pH of between 5.6 up to 7.0.  Many native and adapted Florida Friendly plants vines require an even lower pH to thrive.

Soils with a high pH, such as the urban soils in the Whole Foods living wall planters, restrict nutrient availability (specifically iron, zinc and manganese), stunting planted vine growth and causing yellowing of leaves.

Although some soil amendments appear to have been added during final landscaping, the type and quantity were not adequate to encourage strong plant growth.

There are several simple remedies available to the Whole Foods site.  The living wall was installed in 2010-2011 and could have easily be supporting massive amounts of flowering, fruiting and beautiful vines by mid summer 2012.  Today it is 2014 and the vines still struggle to maintain a tiny about of leaf cover.

But a remedy is possible.  First there needs to be a minor excavation of existing planter soil, both around the front columns and then within the southern wall planter box.  This soil does not need to be discarded.

Second, an appropriate amount of ammonium based fertilizer should be mixed into the soil.  Ammonium based fertilizers typically contain ammonium sulfate or sulfur coated urea.  Ammonium and oxygen react to form nitrite/nitrate, water and hydrogen ions.  The hydrogen ions then work to acidify the soil.

One advantage urban soils usually have is the variety of soil particle sizes and if not over-compacted, can provide for adequate oxygenation of the soil.  Oxygen and ammonium provide nutrients for the plants and help counteract the higher pH of the urban soils.

A quick field test of the Whole Foods planter soils reveals significantly higher than normal  pH.

Amending with organic matter is another possible approach.  Composted pine bark, pine needles, oak leaves, properly composted food scraps can also release both needed nutrients and hydrogen ions into the soil.  Another benefit of the organic mulch route is that earth worms and other soil life will quickly create extensive micro-communities, contributing additional nutrients and providing for nature based soil aeration.

Once the Whole Foods planter soils are amended with the proper amount of ammonium based fertilizers, the soil can be replaced and plants installed.

Of course, care should be taken not to over-fertilize.  Excess amounts of ammonium based fertilizers can burn the roots of installed plants, creating a whole new set of problems.

Native and landscape vines alike can add vertical interest, privacy, screening, color and texture to a landscape project under almost any atmospheric conditions if they are growing in adequate soils.

Remembering that vertical green begins far below the ground is the first step to living wall design and construction success.

Saturday, April 5, 2014

Antique Louis Philippe Rose on the Green Roof

Check out the antique Louis Philippe rose blooming atop the Breaking Ground Contracting green roof in Jacksonville! @greengcjax

 

Florida Green Roof antique roses
Florida Green Roof antique roses

 

Top Ten Florida Green Roof Plants, Salvia lyrata, Lyreleaf Sage

You can not find a better green roof plant than Lyreleaf Sage, Salvia lyrata.  I love to see this very special native wildflower growing across rooftops.

Top Ten Green Roof Plants, Lyreleaf Sage, Salvia lyrata, evergreen beauty
Her evergreen foliage offers an exquisite blend of deep greens, purples and burgundy with leaves laying flat against the ground and flower stems extending vertically to about 18 inches (45 cm).  Note the lyre shaped leaf form.
Foilage - Top Ten Green Roof Plants, Lyreleaf Sage, Salvia lyrata, evergreen beauty
Flowers generally are a deep ocean blue but I have seen the occasional white colored flower populations.
Top Ten Green Roof Plants, Lyreleaf Sage, Salvia lyrata, evergreen beauty
Lyreleaf sage's ability to thoroughly cover open soil media keeps weeds at bay throughout the year.  A mature population of Salvia lyrata can provide a dense, luxurious appearance.
Florida Green Roof Plants, Lyreleaf Sage, Salvia lyrata, thick plantings
Lyreleaf sage transplants easily.  If you can not find the plant in a nursery then it is usually readily found in backyards and alongside the roadside in front of most vacant lots here in the southeast.  Just make sure that when transplanting you are not transferring root-knot nematodes from the ground up to your roof project (though the pests usually can not survive the temperatures on a roof).
Top Ten Green Roof Florida  Plants, Lyreleaf Sage, Salvia lyrata, burgundy and green
This special plant will provide you with many surprises.  She will be green most of the winter when other plants have that sleepy brown appearance and provides masses of bee and other pollinator attracting blooms when most other flowers are still just thinking about blossoming.
Top Ten Green Roof Plants, Lyreleaf Sage, Salvia lyrata, evergreen ground cover
Check out our previous posts about this special plant.  Read the Seeds for Green Roof Post about her also!  Planting this extremely hardy and drought tolerant species will pay off in big green roof successes.

Thursday, April 3, 2014

Green Roofs, Rooftop Permaculture and Marketing

Check out this cool website using #GreenRoofs and Rooftop Permaculture as a backdrop to marketing their clothing line.  I like it!

http://www.gudrunsjoeden.de/Ein-Garten-auf-dem-Dach--40251d.html


http://www.gudrunsjoeden.de/Ein-Garten-auf-dem-Dach--40251d.html


Green Roof Plants, Rain-Root Zone and Root Architecture

One of our favorite Florida #Greenroof plant Genus is the Allium genus.  We've also been working with Resurrection fern also - and I love this plant.  Resurrection fern,  Polypodium polypodioides, was the first fern in space - going up on a 1997 Space Shuttle Mission to see if the roots would absorb water in a space capsule.

Green Roof Plant Root Architecture - Florida Extensive Green Roofs - MetroVerde
Both of these plants, the Allium and R. fern can have unique root characteristics, depending on how they are raised by the grower.

We call plant root structure by the name - 'Root Architecture'.

Green roof design has unique root structure and root architecture requirements.

Unless you have an unlimited potable water or well water source and are going to pump all that water up on a roof to keep plants up there watered, then your green roof plants need to be somewhat drought tolerant.

Certain root architecture patterns support plant acclimation to drought conditions better than others.

Remember, Florida's rainfalls usually are short, afternoon events of 1/2" or less and because rain generally occurs between the hotter months of the year - June - September, there is a tendency for it to evaporate quickly.

Except for hurricanes and tropical storms, rain events in Florida are usually over relatively quickly.

Meaning green roof plants have to scramble to grab the rain water.

Also recall, most green roof plants do not like wet roots (wet feet) so the soil must be well drained.

Proper green roof plant root architecture is crucial for providing a Florida extensive green roof plant with the advantages needed to survive a Florida vegetated roof.

Examine the diagram below showing the root architecture of a green roof plant raised in a one gallon standard nursery container and then a green roof plant raised in a built-in-place green root extensive planting bed.

The plant raised on the built-in-place green root extensive planting bed possesses 8 times the amount of Root-Rain surface contact area as the same size plant grown in a nursery container.

So when the afternoon 1/2" rainfall (13mm) event occurs and every drop is important - the green roof plant with the appropriate root architecture will sequester the most water.

More stormwater is captured, runoff is reduced, plants acquire necessary water volumes, plants have less of a tendency to uproot in high winds, and more.

Green Roof Plant Root Architecture is important to the success of a green roof.

Evergreen Florida Living Wall Vine, Trachelospermum jasminoides

Here is an nice example of how vines can be used in tropical climates to create expansive living walls.

Florida living wall vine, confederate jasmine, Trachelospermum jasminoides

Growing in sunny Orlando, Florida, the confederate jasmine vine, Trachelospermum jasminoides looks to be about 50 feet tall (15 meters).  The vine has grown very woody and thick over the years at the base but still is relatively full and green from just above the vase up to the top most portion.

Florida living wall vine, confederate jasmine, Trachelospermum jasminoides
Confederate jasmine is a reliable landscape vine though it is not a native plant to the Florida area, however the University of Florida classifies the plant as a Florida Friendly landscape plant.  Importantly, unless the plant is installed in properly amended growing media, it may struggle.  Many times I have seen confederate jasmine installed in non-amended urban soils with concrete debris and high pH soils and in these instances it has struggled to establish itself, sometimes looking ragged in leaf appearance.

But once the plant begins to grow, it provides significant, evergreen foliage cover and fills the air with perfume-like scents when the flowers bloom during springtime.  This specimen was growing up and across a very heavy-duty appearing metal pipe and channel trellis.  A smaller, less sturdy system may have a hard time holding the weight of this mature vine.

I did take note of the building owner removing a grouping of old established confederate jasmine vines from another section of the building.  It is possible that because of the educational efforts of local, state and regional native plant groups that the vines may be replaced with native evergreen flowering varieties such as coral honey suckle, Carolina jessamine of others.  I personally prefer using native vine species for Florida living walls, both decisions and evergreen depending upon the application and whether solar gain issues come into play.

Living walls seem to do much better here in Florida if they are vine based, rather than vertically planted ornamentals.  The 5 H's of hurricanes, heat, humidity, hard frosts and high winds act brutally upon vertically planted ornamentals here.  Vines, on the other hand seem to adapt nicely to creating Urban Core Vertical Green if, as mentioned, the soil is amended appropriately.

For an interesting look at a very expensive living wall trellis system with struggling plants, read our series of posts here, pointing to the importance of properly amending urban soils before planting living wall vines.

Tuesday, April 1, 2014

Biodiversity, Habitat and Florida Urban Green

Vertical green in the urban core is so important for biodiversity and habitat.  Unappreciated weeds have significant ecological value.  Here is a short clip about 'weeds' growing in concrete and wildlife.

Imagine if the sides of bridges were intentionally landscaped as part of construction!