Sunday, September 5, 2010

Best Green Roof Plant for Florida and Southeastern US - Green Roofs and Living Walls

Couple of posts back we spoke about how we are working with green roof plants to 'acclimate' each to the conditions they will experience on a green roof.

Today I am writing about a non-cactus or succulent type, but a herbaceous plant species that I will heartily recommend for any green roof in Florida or in environmental with similar ecoclimes.

Acclimation is an important word in the business of horticulture and arboriculture  Acclimation is generally defined horticulturally as the plant's ability to adapt to environmental conditions.  A plant that can adapt usually survives.  One without an acclimation ability may die under extreme conditions.

As mentioned previously, we've been working with greatly reduced irrigation schedules on some of the green roof plant species we use.   We've found some species that over time acclimate really well, while others do not.  Ultimately we took the test to the extreme to find the species that would survive the harshest of greenhouse-prep conditions.

Now realize that even the worst of greenhouse conditions only approximate what a Florida vegetated roof can experience.  Greenhouses for example are usually sheltered from hard, hot desiccating winds Florida vegetated roofs deal with.

And even though greenhouse temperatures may reach well into the 100  - 130 degrees F (50 - 55C), roofs can get hotter.

In the end we found that one species out-preformed all others, consistently.  Even reducing the watering down to no irrigation over a 90 day period - pretty amazing considering the plant is herbaceous and the soil availability for each seedling was 1" by 1" by 3" (25mm x 25mm x 77mm).

At the end of the testing period the soil was usually hard as a rock - brittle like.

After two years of acclimating the plant under minimal irrigation (less than 1/4" per month) - we planted the seedlings on one of our harshest trial roofs - and they thrived!

The species we are referring to are several within the Allium genus.  Most notably, Allium canadense, acclimated by slowing down metabolic processes - going into a state like hibernation during times of environmental stress.

Allium canadense can be found growing along many of Florida's highways - tolerating inundation and drought.

Here you will find photos of a Allium seedling over two years old taken in June 2010.  Following the seedling picture is a photo of the same plant three months later after being placed on a test green roof (non-irrigated - extensive).

Green Roof Plant - Florida Extensive - Acclimation 

Florida Green Roof Plant - MetroVerde - Allium - Extensive, Non-Irrigated

Allium's show great promise as Florida green roof plants.

There are many species to work with from within the Allium genus.

The use of A. Canadense may contribute to a successful green roof planting of native species that are evergreen, that flower, clean stormwater, create habitat and are beautiful.

You may email me with your questions here.

Happy Green Roofing!  Kevin

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