Friday, March 18, 2011

Green Roofs & Invasive Plants - Wisteria, Wisteria sinensis

Botanical name : Wisteria sinensis
Family/Famille : Fabaceae
We have spoken about invasive plants and green roofs here in these posts before. 
The most recent discussion centered around Nandia, Nandina domestica and the Gainesville Regional Utilities Greenroof project. Fortunately, with the help of the Florida Wildflower Foundation the Nandina was removed from the planting schedule.
Yet another beautiful but invasive plant species green roof designers should be aware of is the very hardy and drought tolerant Wisteria.
Wisteria sinensis

Wisteria or Wisteria sinensis is listed by the Florida Exotic Pest Plant Council as a Category 2 plant.

I am the first to admit the attractiveness and scent from wisteria is almost too alluring to resist. However I have also seen first hand the damage the plant can do as it is practically choking to death many of the large sweetgum trees on our Urban Farm. One part of me says - it is worth the color and beauty but then common sense kicks in and I realize we must take care with the plants we use in our landscapes and especially on our green roofs.

There are many alternatives for green roof plant use including both native species and landscape friendly species - species not native to an area yet also not considered invasive.
As mentioned in the post:

"The Florida Friendly Landscape program, an effort of the University of Florida and Florida's Water Management Districts, offers a concise and effective website for designing with ecologically friendly water conservation and ecological concerns.  Moreover, the website offers an interactive online design program to assist in selecting eco-friendly landscape plants.

Additionally, the Florida Native Plant Society offers many resources focused on preserving native ecosystems and plant communities.  Their Education and Outreach webpage makes available an example list of public gardens and natural areas using native plants for landscaping."

Ultimately, green roof design must be approached with consideration for many factors most of us do not consider, such as;

  • Native or exotic invasive qualities
  • Drought resistance
  • Wildlife value
  • Fire fuel contributor (high volatile oil content - remember how dry xmas trees burn!)
  • the 5 H's and much more.
Green roofs are a popular trend within the green building industry today.  The offer important benefits including;
  • Cleaning of nutrients from stormwater runoff (if the roof and stock plants are non-fertilized)
  • Providing much needed vertical green habitat to Urban Core wildlife (such as the green Florida anole - which in turn provides superb integrated pest management)
  • Creating beauty for people
  • Sequestering Carbon and CO2 and providing fresh oxygen as a result of photosynthesis, and more.
We must though, be aware of how we embrace green roofs.  We must take into account all issues, especially those with potential impacts on our ecology and environment. Selecting green roof plant species if a good place to start in designing a Florida Green Roof.

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