Why irrigate green roofs????

Another Reason Not To - Click Here...

Green Roofs, Irrigation, Florida & Hurricanes

Hurricane - High Winds & Non-Irrigation Tests for a green roof test panel. We are collecting data, working with a major university to measure hurricane effects on a non-irrigated, lightweight extensive green roof.

The test panel is a 4' x 10' simulated roof capable of being raised and lowered from a flat elevation to a forty five degree angle.

The vegetated portion is non-irrigated and less than one inch thick.

The panel is being tested under hurricane wind speeds in a wind tunnel. It is also under study for plant growth and survival characteristics under a no-irrigation environment where the insulating qualities are being measured also.

Stay tuned for more information!

Green Roofs in Florida and Irrigation. Is irrigation really necessary for green roofs in Florida?

Here we go again! The draft stormwater manual compiled by the Florida Department of Environmental Protection states that 'Green Roofs in Florida must be irrigated.'

The above statement is simply incorrect and is not a statement we should be hearing from the agency stressing xeriscaping and water stewardship!

I am immediately shut off when I even bring up the topic by many.

Why?

I don't know but it is true - Florida Green Roofs can prosper and thrive even without irrigation.

The roof above has done so beautifully! And in-fact is growing water loving sedges this summer (though I imagine they will die when the dry winter hits) - I suppose birds or the wind dropped seed.

Choose your plants wisely. Plant green roofs to survive without irrigation. Be water wise!

Florida Green Roofs, Roots, Liners, Life Expectancy and Shingles

Yesterday I removed one of the original green, vegetated roofs we had installed in Florida - to replace with different plants - an herb garden type.

I was amazed at how the green roof plant roots had attached themselves to the fabric, creating a strong and binding weave - an important consideration here in Florida's hurricane prone environment.

The shingle roof underneath actually looked newer than the day, years ago that I installed the green roof.

Another example of how green roofs can protect the underlying roof membrane (especially non-irrigated green roofs!)

Kevin

Gone mobile! We can now post from the blackberry!

Corie's Green Roof - Jacksonville

Corie Baker is the architect behind the famous Villa Paraiso mansion on the St. Johns River in Jacksonville (see builttotallygreen.com).

Her and her husband have a flat roofed addition on their historic Avondale home - and they wanted a MV Green Roof.

Here is a green roof base installed today.

Watch for more pics as the plants are installed!

Kevin

Life on a Green Roof is Ever Evolving and Constantly Changing - Dynamic Life Cycles of Florida Green Roof

Each new day brings new lessons and data on our Florida Green Roofs.

Our green roofs here in Florida change every day and teach us new lessons each day.

After more than five years of watching plants on roofs I never saw Bahia grass take hold and start to thrive on a vegetated roof. Certainly during the hot drought of February, March and April 2009 here in Jacksonville the grasses didn't show their blades - but today - after a month of steady afternoon thunderstorms there are grasses colonizing portions of our New Florida Green Roof over the detached office building.

I never saw it before and all of a sudden it is here.

Surely with winter it will die back - but the seed heads are full of seed.

We will see if Bahia comes back next spring.

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!

Native Plants and Florida Green Roofs

Every good plant person wants to use native species in their landscape. At least we all confess so anyway. Certainly the term is politically correct and in vogue by most regulatory agencies, municipalities and various conservation groups, native plant societies and NGO's.

I have just concluded several years native plant trials on flat and sloped green roofs - extensive green roofs that are not irrigated or fertilized. I've traveled across the State of Florida to various plant nurseries and native plant nurseries. I've purchased and accepted as free native plants to try on the roofs. We've watched them through 20 degree F weather and then through 150 degrees in the summer. Earlier this year we had an 11 week stretch where we received less than 1/2 inch total rain.

Roofs are a rough, tough place to put plants. Most have little concept of the harsh and unhospitable environment most roofs possess. The winds alone over Florida roofs are desiccating and will dry out most plants in a matter of hours.

Plants with high stomata to leaf surface ratio are doomed on a roof. Plants that cannot tolerate high humidity and sever swings in daily temperatures - 60 degrees F is not unheard of - are also doomed.

But Florida's sandhills and xeric uplands support native species with a promise of being able to tolerate the ultimate test of life on a roof.

Native grasses make it for a season or two, but the constant winds weaken their resistance and ultimately they fall prey to extreme drought or cold. We've looked at the leathery leafed native vines- railroad vine, for instance and again - though it comes back when planted in the ground after a hard freeze - it has not reliably recovered on the roof.

The native Allium canadense - or nodding onion - also shows promise.

Yucca's, such as the native Adam's Needle are strong contenders however they have a tall habit and may outgrow a roof.

Of course there are many South African and European plants that survive and prosper in these conditions. But they are not natives.

So why not irrigate? We have a water shortage and a mold problem in Florida. The first time an irrigated vegetated roof leaks and causes building mold issues, precedent will be set for every other building with vegetated roofs and mold, regardless of a leaking roof or not.

And Florida has a serious water stewardship issue. 50% of all potable water use right now is for irrigation. Good enough reason to not irrigated a vegetated roof.

Many will never be convinced of the irrigation issue - but we are making progress. Native can work. Finding the right species for the right roofs takes time.

The above pictures are of Elliot's Lovegrass on a flat trial panel and Allium canadense on a sloped roof.

Send me your thoughts... & Happy green roofing!