Green Roof Plants - Frost Damage - Florida Green Roofs

Note the frost and freeze scarring on the above plants. Most of the above scarring is minor. These however are the hardy ones (in the winter... - the summer is another story).

Last night the Channel Four weatherperson indicated that this winter had been the coldest since 1985. In my opinion, it has been the hardest on Green Roof Plants since we started putting plants up in the roof gutters years ago to see ow they'd survive.

We have seen day after day of daytime temperatures in the high 70's (F) with high relative humidity just to have a front come through and dry out the air and drop the temperatures into the low thirties and even mid-twenties (F). That is a fifty degree (F) temperature swing.

Add the desiccating winds and damaging hard frosts and you can see why Florida is so hard when it comes to specifying reliable green roof plants.

But the valuable information is being accumulated! We know what plants are reliably evergreen and can withstand the temperature fluctuations and more!

Wow. Florida Green Roofs are an exciting challenge!

Happy Green Roofing. Kevin

Native Plants for Green Roofs - Florida

Using Florida Native Plants on green roofs can produce positive ecological results. First, native plants should be acclimated to the local climate and ecotone thus affording greater long-term survival. Second, native plants on a green roof will provide habitat, food and foraging opportunities for local and transient wildlife.

Thirdly, the use of native species is an important step in moving towards restoration of original volumetric green in our Urban Core.

The species pictured here include dwarf love grass, muhly grass, Carolina jessamine, a naturalized Florida rosa species and others.

Happy Green Roofing! Kevin

Raising Green Roof Plants from Seed - Green House or Ground? No - The Roof!

Tip for the day:

When growing Green Roof Plants from seed - if the destination roof is available for use - grow the seeds on the roof. You will be building acclimation into the plants as they grow and minimize transfer shock.

The plants will be familiar with the light levels, climate, winds and morning dews.

The pictures above are the recent Feburary hard freeze showing on seed trays placed on top of a soon-to-be Florida Green Roof! Once the seedlings are mature the mat and liner will be installed then the plants placed into their permanent Green Roof Home.

Happy Green Roofing! Kevin

Florida Green Roof Plants Withstand the Hard Freeze of February 5th, 2009

Look at the spread in the temperature range. It was in the low twenties at 5:30 am this morning - now at noon the surface temperature of the trial asphalt shingle roof is 120 degrees F.

How do the plants survive?

The above pictures were taken this morning about 7:45 am.

The plants were frozen solid. But they've thawed and are enjoying the sunshine now!

Happy Green Roofing. Kevin.

The Stress of Cold - Frosts and Freezes - on Florida Green Roofs

Tonight was the coldest night of the year with freezing temperatures reaching all the way down into south central Florida. It is still in the low to mid twenties in Jacksonville at 5:33 am.

Green roof plants have taken the brunt of the cold - sitting up on a roof, dessicated by the never relenting north winds, unprotected and exposed.

These same plants must survive in the extreme temperatures and humidity levels of the summer also.

I will be posting pictures later this weekend. Some of the plants are bit back and scarred, some may have died - but others are doing OK.

My favorite - Allium species - is a testimony to successful green roof plants....it never fails.

Post your results here too!

Happy Green Roofing - Kevin.

Florida Green Roofs, Green Roof Plants and Freezing Temperatures

Just got back from Tampa again. I came across some native grasses along the way at a small nursery - and brought them back to Jacksonville. They are low profile grasses - nice green color and light, flowing texture - especially for Winter!

I have already placed them up on the roof.

The weather forecast is calling for temperatures to hit the teens to mid-twenties across North Florida - and into the twenties all the way down into south-central portions of the state.

Record temperatures are expected (record lows that is).

Of course, Judy and I covered our citrus and some of our tender landscape plants.

But the exciting part of the cold is to see just how 'hardy' plants are on the roof. Some of my green roofing plants took a hard hit two weeks ago. They didn't die, but sustained some scarring. Others made it through the cold just fine.

One of the more interesting observations I've seen this cold season is that you can have two identical plants on the roof but one plant has been installed earlier in the year and has had a chance to 'harden' off to the harsh reality of the garden roof, while the other freshly installed plant has not. Not surprisingly - the non-hardened off plant suffered much more damage than the plant installed in the late spring.

This tells me that there are ideal months to install green roofing plants. I'd suggest it is best to install cold-hardy plants during the cooler months and cold-affected plants during the pre-summer season (allow the roots to develop and grow into the engineered medium before the stressful weather hits.

I'll update the condition of the native grasses after tonight's hard freeze.

Happy Green Roofing!

Plants for Green Roofs in Florida

Wow. I drove to Tampa from Jacksonville this week and witnessed first hand the damage last week's twenty degree F temperatures did to horticulture across the state. We must all remember that even south central Florida may be subject to hard periods of cold, freezes and frosts.

Balance. The word that kept popping up in my mind was 'BALANCE'. In designing a green roof for Florida we must keep in mind the 5 H's (they have grown to five from my initial three) - Hurricanes, Heat, Humidity, Heavy Winds and Hard Frosts.

Choose your planting scheme to include three components!

Number One - use the standard green roof plants that survive no matter what. These include plants that come through hard freezes and boiler-type humidity periods. There aren't many of these but there are a few...

Number Two - Select some of the Sedums that will thrive in the winter. They will limp through the summer though. Their poor summer performance can be offset by Number 3.

Number Three - Select those plants that thrive in the summer monsoons but limp through the winter.

A good green roof plant designer will be able to deliver year-round color and interest.

Remember - we focus on non-irrigated Extensive Green Roofs. Roofs that are light weight - no more than a couple two or three inches think.

Florida is tough on Green Roof plants.

Hands on experience through many years or trials is what will produce the best design for each Florida location.

Happy Green Roofing!

Kevin

Propagating Green Roof Plants for Florida Green Roofs

Propagating plants for green roof projects here in Florida is an important component of a successful Florida GR project.

Knowing a plant was raised in the same ecotone where it will ultimately be used is important. This not only secures LEED credits for local material use (and other credits) but it helps in knowing the plant can survive local climatic conditions.

My general rule of thumb is that, here in Florida, a green roof plant should be grown no greater than 150 miles north or south f the project physical location - no general limit on east/west other than the local limits for LEED credit.

The roots shown on the succulent leaf here developed on their own, on a leaf dropped as mother plants were being pruned, a testament to the hardiness of plants. The above pictures also show the importance of saving pruned plant material for propagation - and in doing so being a good steward of resources.

Happy Green Roofing!

Florida Green Roof Project Continues with the addition of more cold tolerant yuccas....

The New Florida Green Roof Project is moving forward! We've added several new cold hardy varieties of Yucca! Stay tuned for more pictures!

Hard Freezes and Florida Green Roofs - Winter (Hard Freezes - one of the many 'H's GRs face in Florida)

Judy and I have been scurrying most every afternoon to cover plants as temperatures have been dropping into the twenties here in Jacksonville. Looking at the Weather Dot Com it appears that around Tallahassee the mercury has hit the low twenties several times. Walking by our green roofs, I look up with frost blanket in my hand and want to climb up and cover the plants. But I don't.

Our green roofs serve as our best trial panels as we've said many times before. I have finally reached the confidence level that allows me to know the plants will survive. Still though, many of the plants on our green roof are hard to find varieties and the cold north winds are desiccating, unrelenting and potentially fatal to humans, animals and plants.

I am always proud the next day to see the plants stand straight and soak up the sun's warmth. Balancing the choice between those plants, like the sedums that can tolerate extreme cold but melt in the fierce pressure cooker like humidity laden summer heat - and the succulents that can take the tropical heat but not the cold has been the key to success.

There are not alot of plants that fit into the category of withstanding both of the above limiting factors. Then you add long periods of drought and long periods of innundation to the model as inputs and the list of plants that will survive shrink even more.

Finally add the requirement the plants must still look good and not be dormant to the above and the list really becomes small....

So as I await days light to see what damage, if any has been done and add the findings to our resource base - I hope the coldest night so far of 2009 will produce the same positive results as those before.

Happy green roofing in Florida!

Succulents for Green Roofs and more Sunday Night musings...

The blog data here is a continuation of my previous Green Roof blog. Feel free to refer back to the site to my new Green Roof blog because it does contain alot of information - and I will be posting the same info both here and on the Green Roof for Florida blog for some time.

We use succulents in most all of our green roofs. Succulents are an excellent green roof plant in many different ways. Succulents generally store water in their stems and leaves in significant quantities. Cacti leaves are practically non-existent and most photosynthetic functions in cacti occur in the stems. Succulents have stomata on all green surfaces but at much lower surface densities than most other plants.

Because succulents store water they can survive and in most cases still 'look good' after a significant drought. Another benefit to succulents is one of offering a deterrent to fire through their water filled leaves and stems.

Some other drought tolerant non-succulents such as the sages and grasses produce flammable volatile oils that can add fuel or accelerant to a fire.

Most succulents do not need fertilizer in quantities required by non-succulents. We have seen the base nitrogen content in rain provide sufficient nutrients for many green roof succulents.

Succulents also do well in well-drained soils that will wick and absorb a minimum amount of water.

Today engineered soils, such as the MetroVerde engineered soil blends have taken the place of most 'dirt' on the roof.

And finally, we are now prepared to say in our opinion, the green roof plants we propagate and raise like round rays and pots better than square ones.

After viewing first hand the growth qualities and characteristics of our green roof plants grown from seed in round and square containers, and cuttings in both, we believe the round container has less negative impact on root formation than the square shape.

Although there is not a huge significant difference, we've noticed a definite difference in size and in transplanting issues.

Unfortunately round pots are not as space efficient as square pots.

Has anyone out there seen studies conducted on the difference between square pots and round pots? I'd like to hear from them.

Happy green roofing!

Irrigation for Green Roofs. Have you already made up your mind?

A great article on green roofing technical issues by Kelly Luckett appears on a recent Green Roof Website and I recommend the read - lots of good info.

You can find my comments to irrigation issues as follows: (Note - I am pretty much against irrigation on a roof - too much tort liability exposure in my opinion remember Byrne v. Boadle from 1L?)

Hello Kelly:

I read your article on irrigation with interest.

I'd love to talk with you about how you can design a green roof to survive without irrigation.

I understand you may consider it hard to do, but it is very possible.

As a plant biologist for many years and a Florida nursery owner with my wife we too have held a great interest in green roofs, and have trials that have been in the field for years.

Now Florida is different from anywhere in the nation. We have the four H's - heat, humidity, hard freezes and hurricanes. And also a bunch of attorneys who got rich off of mold litigation and are looking at any irrigated roof as a lawsuit, arguing the mold in the building did come from the irrigated roof...

Lawyers aside, we wanted to develop a roofing system that was cheap and lightweight and would meet product approval for Florida Building Code - stricter than IBC - and was evergreen, could be used on sloped roofs, treated stormwater and provided wildlife habitat.

We tried trays and tray systems and mat systems like XeroFlor - http://www.xeroflora.com/ and everything in-between

We consider our 10 years or so of seeing trials not work, our biggest successes.

Tray based systems will not survive long term in Florida. This is our opinion. We do not represent XeroFlor but we have found mat systems are best for Florida's unique climate.

Florida is quite possibly on the verge of removing ballast, be it LECA or Expanded Clay or gravel from approved roofing materials lists because of hurricane damage possibilities. Imagine a roof full of gravel or expanded clay and a hurricane - now imagine the pellets flinging towards fenestration like a shotgun blast in a 150 mph gust.

Florida typically requires all roofing material to be permanently attached to the roof (DCA Roofing TAC guidance)and typically considers a green roof to be part of the building envelop.

So back to the irrigation...You can do a green roof in Florida without added irrigation - I don't know about north of Atlanta - but here in Florida it is certainly possible.

We have roofs in place that have not had a drop of irrigation from day one. And they are doing very well.

Sure, you see signs of stress during 2 month droughts.

But they still look pretty good...

And you don't have to fool with a mechanical system that can fail - one that supplies pressurized water...

And they do fine without fertilizer, but they like fertilizer too...

We heard the same advice years ago. You have to fertilize and irrigate. But our roofs speak for themselves. No irrigation. No fertilizer. No maintenance.

I spent years watching plants grow in Florida roof gutters, and in the cracks of hot asphalt pavement in over 100 degree heat, with desiccating winds, and watched plants grow in cracks of retaining walls for overpasses, and did they ever continue to grow!

One of my favorite green roofs is located in the roof gutter of the gas station next to our local Blockbuster Movie shop. No one irrigates it. No one fertilizers it. It is there year in and year out.

Maybe green roofs can be designed, installed and survive without irrigation. We know they can here in Florida...even with our harsh sun, heat, winds and storms...

I smile every time I read of someone saying it can't be done...

Green Roof Planting Media - Second and Third Generation Products

After literally thousands of soil mixture experiments we are making strong headway in developing the green roof soil medium that has the qualities we are looking for. As we look back over the years we can readily see how far we have come.

We've addressed the drainage and the flammability and the dust and the compactability and the water retention and the nutrients/organics issues.

Erosion was a huge issue that we wanted to resolve. Our focus was on lightweight, thin (low profile - primarily because of Florida's hurricane propensity), inexpensive vegetated roofs that would not only work on flat roofs AND we wanted our roofs to work on slopes - even severe slopes!

Today I installed a 20SF vegetated panel on a vertical wall at the house, less than ten minutes after the engineered soil and plants had been applied. Wow. We have come a long ways.

But we have a long ways to go.

Now that flexible vertical vegetated panels - less than 1" thick are a reality - now we are looking at technology that will allow us to apply vegetated panels directly overhead on ceilings. So here is the next challenge.

The era of filling planters or trays with dirt, loose soil mixtures, LECA or expanded clay and placing them on the roof is disappearing. Like the dinosaurs these applications will hang around for a while, with good usefullnes with large heftily
-engineered structures. LECA and Expanded Clay may soon be against building code in Florida for use on roofs - imagine a truck bed load of LECA pellets fling through the air in 150 MPH winds - something like a shotgun blast.

Toxicity free engineered planting media will be a requirement. LC 50 testing with minnows will become standard. Green building requirements will affect planting media design too.

The challenges are here - so are the opportunities...

Happy Green Roofing! Kevin

Choosing Plants for Green Roofs - The Season for Sedums to Die in Florida

Tis the season for some sedums to go dormant in Florida....

We have had a month of drought. The days are becoming shorter and shorter. The winds are brisk and desiccating. Temperatures have ranged from 60 to 80 degrees F during the day and 30 to 60 degrees F at night.

We have had three light to medium frosts.

Too much for some of the sedums...

The alliums are turning brown on top too - the brown curly cues typical of drought.

The Florida climate is the biggest drawback to using sedums on Green Roofs - at least don't count on the succulents being your prime plant...

They usually come back out in the spring.

Happy green roofing!

Green Roofs use of Expanded Clay and Lightweight Expanded Clay Aggregate

The State of Florida has recently requested studies analyzing the use of gravel and aggregate on roofs and the potential of gravel ballast to break windows and other fenestration components of a building during hurricanes.

Preliminary research by the University of Florida shows that gravel ballast may be the cause of unnecessary glass failure and subsequent water damage.

Hurricane Alicia in 1983 devastated the Houston area, and much of the urban fenestration damage was attributed to gravel ballast ripped off the roofs by the hurricane force winds and shot across the city like pellets.

As Florida's green roofing industry develops, designers should be aware of the potential for tort damage liability once their specified product damages anothers property.

We should be careful about placing any gravel or pellet like material in a green roof until all the appropriate studies have been conducted to determine the level of safety for such product use.

Frost & The Florida Green Roof

Tonight is the second night of the November 2008 winter where the outside temperature is expected to drop below freezing. Last night there were low in the mid to low 20's all across North Florida and the same is expected tonight.

Expected seasonal weather like this creates a huge challenge for the vegetated roof designer in Florida. Not just cold weather alone - because many northern green roofs survive much colder temperatures.

No - it is the combination of two weeks ago we were experiencing heat and humidity at high levels and now the frost - little if any hardening off of the roof plants.

I pose a question here. What happens when many of the native plants here that are deciduous or produce leaf litter - what happens when leaf matter dies from frost or drought? One of the answers is that we see a marked increase in leaf litter buildup.

Leaf litter turns into fuel once ignited. Dead plant matter, dried by desiccating cold winds can easily and rapidly burn when exposed to a spark or heat source.

Fire occurs in nature to cleanse dead plant matter from the environment and return nutrients to the soil. The chance of a roof fire increase once flammable, dried leaf litter accumulates on a green roof.

ASTM has recognized this potential problem and is developing standards for green roof plants.

The good designer will also strive to incorporate plants that prevent or greatly reduce the chances of leaf litter build up.

As we enter the season where many plants are dropping their leaves and becoming dormant, we should ask ourselves as we design green roofs, about potential fire issues with the plants we are selecting.

Better safe than sorry.

Green Roofs in Florida and the Southeastern US. Insulation values for real?

We can all assume that thick intensive green (vegetated roofs) provide a measure of insulation - but what about thinner, extensive green roofs? Do extensive green roofs, say 2 to 4 inches thick provide insulation benefits?

Jincy, Ruairi and I have tracked the insulating factors of several extensive roofs, comprised of the MetroVerde mat roof system during the 2008 summer season.

What we found was very interesting.

Using a Extech Infrared IRC40 thermal imaging unit we measured the temperature of the roof decking undersides for roofs with (A) extensive 3" thick mat based vegetated roofs planted with allium and iceplant, and (B) asphalt shingle covered decking.

Not surprisingly, the underneath of the roof decking on asphalt shingle roofs averaged 125 - 130 degrees F during July, August and September 2008.

Temperatures of the undersides of the roof decking below asphalt shingles covered with the MetroVerde extensive mat systems averaged 84 - 86 degrees F at the same time of day.

Moreover, it is expected that the green roof mat system will protect the asphalt shingles from solar degradation.

So do extensive green roofs insulate a roof from solar gain? The answer is an undeniable Yes!

Green Roofs in Florida and Cooler Weather

It is becoming cooler and night now and well should be - it is almost Thanksgiving & most green roof plants on our projects are very happy that the long and tortuous ordeal with Florida's heat and humidity is almost over for a season...

Many of the plants bear battle scars from Tropical Storm Fay (way, way too much water) and the ever present afternoon humidity bath.

The Sempervivums are starting to revive...you can see new growth expanding out from the middle of the plant, the brown, wilted areas falling away from the perimeters.

This is the time of year for dormancy for some of the sedums - - they are turning brown and melting away while others are just melting after a long stressful battle with the Florida humidity.

Iceplant is doing well. Iceplant planted on the ground melted out during T.S. Fay but those clumps on the roofs actually thrived.

Interestingly, the allium likes the cold weather too - its leaf blades perk right up.

So now is a major time for seasonal change in North Florida for green roofs. Stay tuned for more updates!

Green Roofs in Florida -

Palms and/or other trees on roofs present many challenges to the designer. In Florida these issues can include: (1) weight, (2) wind speed uplift during tropical storms or hurricanes, (3) irrigation and maintenance requirements, (4) fire safety and more.

Though I focus on thin, lightweight Green Roof mats (much less expensive) there will be clients who would like to have a roof with trees. Certain challenges are presented to us in designing a roof capable of supporting trees. First and foremost your structural engineer has to provide a deck capable of handling the loading.

We will be collecting photos of Florida green roofs that include trees and large shrubs. Send your photo in to Kevin for posting - along with a description of the roof, location, how long the roof has been in existence and other data.

Holidays are coming up - what better way to celebrate than with a blooming green roof!

Cheers..

Green Roofs can be vertical green vines also - Choosing the right plant and planting system lays the foundation for success.

Try a MetroVerde Shade Trellis! Based on the concept that a deciduous vine will block solar gain during the summer when the leaves are growing and allowing needed heat during the winter months when the leaves are off - MetroVerde's shade trellis combines plant requirements with awning frame design to produce a product that 1. cleans stormwater, 2. provides habitat and 3. creates a beautiful sense of place!