Choosing Green Roof Plants - Why the Equation ""#S/LAmm2lt200"" is so important.

Today we discuss again the importance of understanding leaf structure when choosing the appropriate green roof plant, and specifically the part of the plant most commonly called the stomata.  If you recall from biology class, stomata are the openings in the leaf that allow for CO2 to be taken in and O2 to be released.  The stomata are operated and regulated so to speak by the stomata guard cells.  OK but what does that have to do with Green Roof Plants?  Its important!  Lets see how...

All plants need water in their leaves for photosynthesis to occur.  If the plants dehydrate and have no water in their leaves, they quickly die.

Now envision two plastic bags, one 100 small holes and the other with 10 small holes.  Fill the bags up with water and what bag holds the water the longest?  Same concept applies to stomata and leaves.

Looking at the equation above - "#S/LAmm2lt200" translated says based on our studies - the ideal green roof plant for Florida and the Southeastern US is a plant where the number of stomata (#S) per leaf area in millimeters square (/LAmm2) should be less than 200.  Sorry for the way the equation looked but Blogger kept thinking I was writing HTML code and refused to let me save it any other way - and since I am a plant person (and a lawyer by education too) I didn't want to take the time to solve this issue.

OK but what plants have a stomata ration of less than 200 per mm2?  First of all lets look again at leaf structure.  Waxy plants tend to have lower leaf stomata per leaf surface area ratio.   What are waxy leaved plants?  Some examples are cactus, agave and others. Other plants, typically with a soft, non-waxy leaf have much more stomata per mm2 than the cactus and agaves.

Plants that probably will do well on a low-maintenance, non-irrigated green roof can generally be chosen successfully from the cactus and agave families (and others - we will get to those in another discussion).

Plants such as perennial peanut and other commonly thought of as drought tolerant plants have little or no wax and 4-40 times as many stomata, meaning they loose their leaf water much quicker.

Now the above discussion is really a big over-simplification of the entire process.  You see perennial peanut as much more aggressive operational controls over their stomata - slowing down the opening during hot periods or periods of drought to conserve water.  But the lethal interior leaf temperature on most plants is in the area of 110 degrees F (45 C)and above.

As I've mentioned before in the blog notes I record leaf surface temperatures of 140 degrees F ( 60 C) and under these conditions the plants most all first suggest just do not survive long term on a roof.

So know your green roof stomata equation and enjoy a low maintenance green roof.

Does this mean only cactus?  Absolutely not. 

Waxy leaf plants may be a plant to use.  Those species with tougher, leather-like leaves can also do well.  Then there are those more herbaceous plants that just do well in the sun.

Native species of ferns sometimes have a low stomata to leaf surface area ratio.

A green roof can look beautiful!

Call us and we will help you with your upcoming project.  As always, feel free to email us with your questions.

Check back soon for more species or call Kevin 904-294-2656.

Flat Roofs and Sloped Roofs, Green Roofs for both in Florida

Remember though - the plants you have installed on your green roof generally do not like wet feet, so provide good drainage!

Our field panels have shown that green roof systems in Florida with excellent drainage - nothing to hold the water in the soil - grow the healthiest plants.

Many take the opposite approach and install a water retention layer (material like a sponge - and a good way to grow mold and culture up plant diseases). Though a water retention layer will work when rain events are a week apart - allowing for drying time - the retention layer becomes a detriment during periods of daily rainfall events. All of a sudden the drought tolerant plants are subject to wetland conditions.

Therefore - we have found green roof plants (Extensive Roofs - we do not work with the heavier, more costly intensive roofs) - on sloped roofs do the best.

Moreover, engineered soils will last longer when well drained. Water has a tendency to act as a separation agent (dig down into your backyard and you can tell how high the ground water rises because the water separates organics and inorganics into layers).

Remember - well drained systems last longer and grow healthier plants!

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

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 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!

Florida Green Roof Project Continues!

The new Florida Green Roof continues to grow with more and more succulents, agaves and cacti daily!

Once the structural plantings are completed the oobleck will be added around the plants, allium seeds sown and then wait for the plants to take off and fill out the mats!
Contact Judy @ MetroVerde for your green roof!

Green Roof Plants Bloomin! Florida Green Roof Project

October is a great time of the year for Green Roof Plants! Many of the species with flowers of a red hue are blooming! Email Judy for your personalized roof!

Sustainable Florida! Green Roofs! UCF Orlando October 21, 2008

I attended the Collin's Center Sustainable Florida Conference this week hosted by UCF. The event was eye-opening and inspiring. Our panel presented on the urgent need to restore vertical green to the Urban Core.

Benefits from vertical green in the Urban Core include; A. Stormwater cleansing, B. Creation of Wildlife Habitat, and C. Reconnection of humans to our connections with nature - A Sense of Place Reality in an otherwise electronic world.

Check out the Sustainable Florida Website!

Update - Florida Green Roof Project - with installation of green roofing plants!

Plant installation on the New Florida Green Roof Project proceeding! Looks for more updates soon!

Florida Green Roof Project - Green roofing at dusk...

The plants are under installation. The days are getting shorter. The nights cooler. It hasn't rained for a week and the only water the plants are receiving is the blanket of heavy morning dew.... This weekend we should make good progress with finalizing the plant installation!

Tuesday Morning Reflections - Green Roofs for Dogs - Florida Green Roof Project

We won first place with the above entry in the Jacksonville AIA Barkitecture Contest earlier this summer.

JSA Architects out of Jacksonville was the lead on the team - We did the Green Roof! JSA developed the system to take the vegetation filtered stormwater - filtered through plants and a geosynthetic, and feed the doggy watering bowls!

Florida Green Roofs project - should we use a pre-vegetated mat or install mat then seed/plant?

Great Question! The answer is you can do either! Sometimes it is the logistics that dictate the appropriate option to use.

Pre-vegetated mats are heavier and if they are to be carried up to the top of a tall building, then the transportation can be difficult. Typically, pre-vegetated mats are cut into standard sections then stacked on a pallet. You must first determine that adequate access exists on the project site - consider the size of the pallet, size of elevators, etc...

Installation from scratch is applicable in instances where there is no practical way to carry the pre-vegetated mats to the roof. There are also other instances where you might want to consider installation from scratch. Consult Judy at MetroVerde if you want to discuss what is right for your application.

The New Florida Green Roof project moves forward!!! The Seeds are Sprouting!

It has taken about seven days for the allium seeds to sprout. However they are bursting forth in full force now, even though we are well into the autumn season. Allium is one of my favorite plant Genus'. Allium sp. is a hardy plant - you can find them growing almost anywhere!

Allium's are drought resistant, evergreen and provide significant habitat for all types of wildlife! Watch for more pictures as the plants mature! Be sure to also check out MetroVerde - Judy's website on Green Roofs and Urban Permaculture.

The new Florida Green Roof Project - Next Episode - Installation of the Liner!

New eUrbanism! Green Roofs everywhere! We are refining the available technology - now doing things only dreamed of before.... So we'd like to think.. Our ancestors and those before us had vertical green techniques so much more refined - even though they lacked the polymer and synthetic materials we have today...

Hanging Gardens of Babylon! and also check out Wikipedia's write up...

IFAS at UF has a great virtual field trip website that provides more info on vertical crop growing and hydroponics.... see previous blog...

OK but back to the new vegetated roof. Today was the 20 mil PVC liner installation day and unfortunately it was real windy - a front is coming through -

Normally on a TPO roof there is no need to put a root barrier down - you always can if you want to but the TPO and the PVC root barrier are one and the same material practically and you end up just duplicating efforts.

But hey! If you want another liner over the TPO - put one there. The black pond liners you can find a Lowe's and Home Depot work great!!! These come in various stock sizes. You can get 13' x 20', 13' x 10', 8' x 10' and others. Watch Craigslist for great buys on pond liners as there are many people who buy the liners thinking they will get a 'round-to-it' and build a backyard pond. It is amazing how many pond liners I see for sale on either e-bay or Craigslist!

For sure you would want to put a liner over asphalt shingles - as we are doing here... Otherwise the roots would devour the asphalt shingles eventually...

But over TPO - well - if you are in doubt build a trial panel! See for yourself!

So since we have a asphalt shingle roof on this project - we are installing a PVC liner. (Always follow OSHA safety guidelines when working above ground)...

Folded up, PVC is heavy and will stay put on the roof. Unfolded the liner is like a waiting sail, ready to leap into the air and follow the breezes. Moreover, liners are slick, slippery and a fall hazard on the ground and especially on a roof or raised platform!

Even over rough - friction heavy asphalt shingles, PVC liners will 'slip and slide'!

MetroVerde's belief is that any vertical penetration through a roof will cause a failure or maintenance issue, sooner rather than later, in Florida's harsh environment!

Today's project roof has a 5/12 slope - moderately steep slope...

And today was WINDY! With the front coming through, as soon as I started unfolding the liner - the wind would pick it up and throw it down over the edge...

See the photo's...

But using MeroVerde's patented attachment system, once you get the mat laid out in a roughly positioned posture - then quickly attach the mat and the roof with the first fastener - usually the highest corner in the direction of the prevailing wind.

Install another fastener ever three feet on both the x and y axis. Carefully move across the roof area, installing all fasteners until the entire liner perimeter has been attached to the existing roof. Make sure the liner is stretched tightly across the roof and there is no obvious buckling or 'air bubbles' in the liner.

Usually the weight of the liner will press down and form against the existing roof. Once the MV GRP vegetated panels are installed the weight should be easily sufficient to hold the entire system in place.

See the photos! The final installation photo shows the liner stretched and attached - ready for the mats!

Watch for the next episode! Until then - Happy Green Roofing! - PS - Feel free to call me anytime you wish to discuss Green Roofs! 904-294-2656... :) Kevin

Florida Green Roofs - Prepping the mat with expanded mineral material - perlite, vermiclite, expanded clay, agar, trace minerals, and more!

Episode Three - prepping the planting base - prepping the mat. Lots of standards and regulations, common sense precautions and just plain good BMP's - Best management Practices come into play now that the mat is rolled out. So we've talked to death the reason why we don't like trays and modular systems....Hey I heard of a roofing company somewhere is South Florida who just installed a system of trays on their roof - and the plants died...

But the reason we choose mats is not the reason we don't use trays. The reason we choose mats is because with a mat, the green roof's plant roots can grow as far north, south, east or west they want to grow. No circling (as in trays) and no self strangulation in a couple of years (as in trays).

Sure - maybe Plant A will Run into Plant B. Instead of root circling and strangulation though, the roots will compete with each other and the stronger plant will go onto to survive. The important note here is that there is always coverage - though one may dieback, the stronger or more suited plant survives. The mat advantage has proven itself on the Dearborn, Michigan Ford Motor Company 10 acre roof.

OK - back to the soil...

Wouldn't it be easiest just to fill the mat with dirt from the backyard? - Maybe so - but I wouldn't do it. Think of the weeds, nematodes, fire ants, etc you may be digging up and placing on your roof.

Moreover, ASTM has specifications written for dust and organic matter and more for green roof soil systems. The MetroVerde engineered soil (MV GRP) mixture we use is a proprietary blend - and we add soil goodies to it! I think of it as a stabilized outdoor hydroponic system!

So lay out a piece of plastic sheeting on the ground in an area you won't be walking - please note that if you have outside cats or dogs - they love to use a rolled mat system as a huge litter box! Take precautions!

Roll out your mat on top of the plastic, add the mixture of perlite, vermiculite and expanded clay. Apply the tackifier initial layer. Sow desired seeds or installed pre-grown plugs and reapply tackifier.

We'll explore soil mixtures and tackifier solutions (there are many of these sticky mixtures) in an upcoming post. In the meantime - Happy Green Roofing!!! Kevin

New Florida Green Roof Project - THE MAT !!!!

One of the basic principles of a successful green roof is the base mat. Mats are the preferred green roof base system for Florida Green Roofs - as we have discussed countless times before here. The reason is simple - the roots in plants secured in trays or modular components eventually reach the tray walls and begin to circle around, eventually strangling themselves to death - remember going to the nursery and buying pot or root bound plants - they did not live long....

Welcome to the mat episode...the mat was delivered today! We will unroll it, flatten it out and begin adding the expanded clay, other non-organics and the tackifier (agar based). Sound complicated? Naw.... Watch for the next episode - to be posted later tonight after we do the above tasks! Happy green roofing - - Kevin :)

How Much Should A Green Roof Cost? and more Green Roofs for Florida musings

One of the most common questions I hear about green roofs & vegetated roofs & garden roofs is: HOW MUCH DO THEY COST? Good Question. Easy Answer.

An extensive evergreen garden roof can be purchased and installed from a base price of approximately $6-8.00 per square foot for simple, one species installations to $12-$14 per SF for a moderately top of the line extensive garden roof with multi-texture, multi-color plan species.

Now, if you have more money than you know what to do with - then you can spend as much as you want per SF. I have seen some vegetated/garden roofs quoted in the $120.00 per SF range (YIKES!!!),

It is educational (and I highly recommend you do this if you are interested in green roofs) to go and talk to your local roofer that has experience with installing TPO roofs. A TPO roof is also a 'green' roof if it is white in color - because it will reflect heat! Usually those roofers who have experience in TPO know vegetated roofs also - but always ask them if their company (or parent company) sells green roofing systems. If they do, be sure to make sure you are receiving unbiased info). A good TPO experienced roofer is Rick Anderson with Delta Roofing in Jacksonville, Florida - call Rick at (904) 292-1592 - tell him you saw his name on Kevin's blog.

Green roofs are my passion, and I believe they are key to restoring green to the Urban Core! - Creating habitat, a sense of place, and resolution to stormwater issues.

Don't be scared off by a quote of $20-$40 per SF for a green/vegetated roof! Those complicated and expensive systems are not necessary!

Please - beware of green roofs that require irrigation. Please!!! - it is easy to grow an orchard on a roof with fertilizer and irrigation and cow manure and etc...

A doubter? Look around the next time you are driving through town at the volunteer plants that THRIVE in sidewalk cracks, overpass retaining walls, uncared for gutters, and more. I've never seen irrigation tubing here!

Now - if you are looking at a global system - greywater, reuse, rainwater catchment (Judy and I are members of ARCSA - check out www.arcsa.org), permaculture - then you may want to integrate recycle irrigation into your vegetated roof - but DO NOT BUY the story that you HAVE to have irrigation. I can show you plenty of applications that have successful and beautiful green roofs that grew up on only rainwater...

OK - want to DIY? email me at chockasacka@msn.com

But before you go and spend $ 20+ per SF shop and compare.

One final tip of the evening. We take and set up light level and temperature recorders on roofs we are evaluating for plant applications. Spend some time to assess what you are working with - this is the first step to good planning.

One last final tip. If you want a top of the line extensive vegetated roof - low maintenance but lush, tropical and beautiful - one that will treat stormwater, provide urban wildlife habitat like you will never believe and create a sense of place your DNA will connect to - email me.

Happy Green Roofing!

Kevin

Living Walls provide the same type vertiscaping - vertical green that vegetated and green roofs provide!!!

Great Reference Website for Urban Heat Island remedies and Florida Green Roofs

Check out this website developed by the EPA about Green Roofs - good basic info...

www.epa.gov/hiri/strategies/greenroofs.html

Florida Green roofs - modular trays or mats? Look out for trays that cause root bound results!

Green roofs are popular now and a huge question I have is with respect to plants developing root binding due to the modular tray walls. I am sure there are many satisfactory answers out there however I am yet to be convinced!

With trays and modular systems - not only will the planting media 'float' out of the tray in a heavy storm event, but the tray walls restrict horizontal growth - and all plants tend to grow outward from their original diameter. Once roots start circling they strangle each other, competing for space.

Mats allow for the roots to grow as far as necessary in any direction. If there is another plant in the way, then competition kicks in and the most aggressive species wins over - however the end result is that the green roof system is always vegetated.

Florida is a tricky climate to use any green roof system in - let alone modular systems or trays. Our climate is totally different than the climate up north and though trays and modular systems may work up north - they are much more difficult to make work in Florida.

Of course - if you want to spend $$$$$$$ on maintenance and design then trays and modular systems can be designed to work acceptably, but why spend the extra dollars when the mat systems will provide the same amount of 'green', put less of a structural load on your roof, and do not require irrigation!

Check out MetroVerde's website - they offer a mat system that has proven itself in Florida - heat, humidity and tropical storms (see the posted video of tropical Storm Fay on Green Roofs)

The two photos here are of sedum center dieback from the plant being root bound, and the actual root circling action. Modular trays are not good for the long tern health of the plants on Florida Green Roofs.