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