Florida Green Roofs and Biomimicry, Agavaceae and Dew

Nature offers the finest examples for us to look to when resolving green roof, or any other for that matter, issues.  Today I want to mention plants that catch air moisture, such as dew, and help 'irrigate' a green roof.  Let's look at some of my favorite green roof plants, Yucca and Agaves.

Floria extensive, sloped green roof

Green Roof Plants, Yucca and Agaves - note the hairs and clover, a nitrogen fixer

Yuccas and Agaves, with hairs across the surface edges of her leaves is a highly efficient fog and dew catching plant.

Likewise, with waxy, tough leaves and CAM (Crassulacean Acid Mechanism) photosynthesis, they can serve as the perfect green roof edge wind-break perimeter plant.

Yucca and Agave biomimicry tells us high dew catcher surface area to air mass contact is most efficient for air water vapor to occur. 

Many yuccas and agaves thrive in hot, dry, windy areas and make excellent choices for green roof plants.

Yucca filamentosa, Adam's needle is a favorite green roof plant of mine, reliably hardy in the freezing cold temperatures, evergreen, very drought tolerant, a dew catcher and the perfect CAM perimeter plant.

Yucca filamentosa makes an excellent green roof plant for Florida

Planted in mass, Yucca filamentosa acts as a green roof parapet, allowing interior plants a more welcoming ecosystem for growing.  This green roof plant has not only survived, but thrived on some of our older green roofs!

Yucca filamentosa also has long hairs growing from the leaf edges, allowing for water vaopr in the air to collect as the humid breezes flow across the plant.

Turbulence is another factor necessary to help drop the condensed air water vapor from the catcher to the green roof soil below.

Florida Green Roof  Plants Yucca and Agaves, Note the hairs along the plant edges that facilitate dew sequestration

Success of a nature irrigated green roof depends heavily on sourcing a steady supply of water through rainfall, fog, dew and even frost. Understanding biomimicry based green roof planting layout allows for important air water vapor collection.

Additionally, understanding the principles behind Agave's and Yucca's' water capture successes lie also in an understanding of air humidity.  Humidity is the amount of water vapor in the air. 

Humidity is an important source of irrigation for nature irrigated green roofs and is often present when rain is lacking.  Humidity is often described in terms of ‘relative humidity’ and ‘dew point’.

Relative humidity is the phrase commonly used by weather reporters to communicate the percentage as the amount of actual water vapor in the air divided by the amount of water vapor the air could hold. 

A relative humidity of 75% means air contains 75% of the amount of water vapor possibly held.

Yucca acts as a dew catcher to provide moisture to other Florida green roof plants

Dew point refers to lowest air temperature where water vapor remains in vapor form.  Once the ambient air temperature reaches the dew point temperature the water vapor condenses into dew or liquid.

Dew and fog reference and collection resources available on the web include;

• Fogquest.org is a great informational resource on capturing dew and fog 

• Youtube video on dew catcher construction

Air humidity can be a significant component in the irrigation of any green roof system.  Consider those months with lower than average precipitation and check to see if dew occurs frequently.  Validate the average relatively humidity percentages.  

Think of the times you have walked across a lawn in the morning to find your shoes soaking wet.

Research dew and fog collection websites.  Look to the green roof plants you work with to see what species appear to accumulate dew. 

Mimic nature.  Mimic the Yuccas and Agavaceae.

Florida Green Roof Images, Herbs and Roses on the Roof

Herbs on the Florida Green Roof.  Parsley, sage rosemary and thyme.  Yesterday Breaking Ground Contracting #GreenRoof photos.

Green Roofs in Florida, rosemary and garlic chives, herbs on the roof

Green Roofs in Florida, Louis Philippe antique rose and Florida native yucca filamentosa

Green Roofs in Florida, aloe and yarrow growing on the living roof

Green Roofs in Florida, aloe is such a great rooftop medicinal plant, drought tolerant & hardy

Green Roofs in Florida, aloe in bloom on the rooftop

Green Roofs in Florida, Louis Philippe rose buds, such a lovely rooftop plant

Ethnobotany for Green Roofs, Achillea millefolium, Yarrow on Florida Green Roofs

Rooftop ethnobotany should be a part of all green and living roofs as plants have given humans food, fiber and medicine throughout the ages.


One of my favorite green roof plants rich in ethnobotanical history is Yarrow.

Green Roof Achillea millefolium, ethnobotanical wonder and living roof beauty

Yarrow is a hardy Northern Hemisphere native wildflower suited for hot, dry green roofs. Yarrow is found growing as a native plant around the world in the northern hemisphere. 

Her Mexican name is plumajilla or ‘little feather’ due to the feathery shape of her leaf.
Important to biodiversity support, many birds (including sparrows) use the soft leaves of the plant to line their nest.  The leaves are quite soft and add a blanket of light green color across the green roof for much of the spring and early summer.  When the blooms began to appear during late May and June the plant sends up shoots, supporting beautiful umbells of flowers. 

Green Roof Achillea millefolium, Breaking Ground Green Roof

Yarrow has a rich ethnobotanical history having been used for centuries as a wound herb, and is famous for the capability to stop bleeding from cuts. The leaves may be used as a spinach like vegetable, cooked or in salads.  The plants has also been used as a flavoring in beer. Yarrow has EO data suggestion insecticidal qualities against common mosquitoes.

MetroVerde Green Roofs supporting biodiversity on many levels, Yarrow

Yarrow can tolerate hot, dry soils with little organic material.  A member of the Asteraceae family the plant is very drought tolerant once established. The flowers add a variety of surprisingly bright color to the green roof as many other flowering plants are seeding out and loosing their color.  The perennial plant usually comes back and flowers reliably, year after year.

During the harvest season when most green roof plants are beginning to wear a tired look from summer's heat and humidity, Yarrow is just beginning to develop a rich, deep rainforest-like green hue.

Shown growing here with Pennywort, Hydrocotyle spp. and Aloe, Yarrow serves as a weed blocking  groundcover worthy of any living roof.

Green Roofs in Florida

Lots happening in Florida with respect to green roofs.  To bring you up to speed here are a few noteworthy items of interest:

Genora Crain-Orth will be interviewed on public radio this morning here in Jacksonville about her efforts to secure permission for a small green roof on her historic home.  The interview will be aired at 9 am EST and can be heard online around the world from WJCT, First Coast Connect'd live stream.

Genora's living roof may be small but the impact is important.  She has placed a vision into action.  Those visions we have, once placed into action can change the world.  You can also read more about Genora's living roof here.

Secondly, Sustainable Florida is hosting the 2011 Sustainable You conference in Tallahassee this week.  You can see the green roof presentation slideshow here!




Thanks to Breaking Ground Contracting for use of some great slides and photos!

Thirdly, a live video filming on the Breaking Ground Green Roof will be taking place Thursday, October 27th, 9 am EST.  The focus will be on the newly emerging winter food crops.  Interested adults are invited to attend by RSVPing Catherine Burkee.

Jimmy Sterling and I are headed to South Florida next week to design a 6,000 sf rooftop garden!

The Jacksonville Zoo green roofs are coming up in November!

Florida is leading the way in the south for green roofs!

3 Most Important Reasons to Build a Green Roof in Florida

There really are lots of good reasons to build a green roof in Florida and across the southeast United States.  The three reasons to build a vegetated roof here in Florida that I use most are:

Reason # 1 to build a green roof in Florida.

You will clean stormwater and help reduce runoff.  Our observations and data recordings have shown that on rainfall events of less that 0.50 inches ( 13 mm ) the plants and soil on the green roof capture and hold the rain - thus reducing the amount of stormwater runoff leaving a site.

Now all roofs reach a saturation point and will begin to discharge rainfall as runoff however since the majority of rainfall events we have here in Florida are less than 0.50 inches ( 13 mm ), then the green roof is capturing most of the rainfall.  This helps keep nutrients and other pollutants out of the stormdrain and out of the river.

Reason # 2 to build a green roof in Florida.

You build the green roof and the wildlife will come.  We have long seen that once a green roof was installed - wildlife, including green and brown anoles (lizards), tree frogs, lady bugs, butterflies, dragonflies, hummingbirds and other species visit the green roof in mass on a regular basis.

Research shows that many species are dependent of vertical green - or green up off and above the ground for survival - to escape predators.

The reemergence of native wildlife around your green roof will provide many benefits ecologically, not the least importance-wise is - an integrated pest management system.  You will notice a great decrease in fly, roach, termite and other pest populations as the lizards and tree frog population numbers grow.

Reason # 3 to build a green roof in Florida.

They are beautiful, provide oxygen to a hot city, take up and sequester carbon dioxide and give us humans a sense of place - a sense of belonging - in an otherwise hot urban concrete or asphalt setting.

So there you have it!  Three most important reasons to build a green roof in Florida.

Happy Green Roofing!
Kevin