Thursday, September 9, 2010

Green Roofs Clean Stormwater - Help Protect Florida's Springs

Florida has a thick layer of limestone bedrock throughout much of the state.  Over time water has eroded channels throughout the stone, creating areas where the cold, clear subsurface water flows up and out into rivers.

Exotic and pristine.  Water from hundreds and hundreds of feet below the surface roiling up out of the g round.

Blue Hole, Itchtucknee Springs, Florida

Under the pressure of nutrients and pollutants associated with growing populations, Florida's springs are directly affected by nitrogen and phosphorous found in fertilizer.  The water in many of Florida's springs are now becoming filled with algae thriving on the polluted stormwater that flows off roofs, yards and roads into the limestone aquifer.

As green roofs are one of the best first line defenses of Florida's groundwater, care should be given during design and maintenance not to introduce additional nitrogen and phosphorous from fertilizers into runoff.

In fact there are many good reasons to minimize or eliminate fertilization on green roofs, including cost of the ongoing fertilizer applications (labor and material), avoidance of potential pollution and more.  Herbaceous plants exposed to fertilizer may exhibit weaker acclimation characteristics.

Look for a blog post coming up soon discussing ways to eliminate fertilization from green roofs.  Some of the approaches we will be looking at will include; companion planting with trace element producing and /or nitrogen fixing plant species, native xeric species, designing with an understanding of NOx rainfall content (especially for the Urban Core), slow release v fast release fertilizers, organic v inorganic, etc...

Unfortunately, too often will a green roof landscaper or designer either schedule a heavy regime of fertilization or hoping to make stressed green roof plants look better, add a coating of nitrogen rich pellets.

Doing so shows a lack of green roof design and natural resource stewardship understanding.

Florida's springs are fragile and cannot process significant N and P loadings.  And green roofs are supposed to be an environmental positive - not a point source for pollution.

I'm looking forward to discussing alternative solutions to green roof fertilization and would appreciate your comments and experiences here.

Protect Florida's Springs - Install a Green Roof

For more information on Florida's unique springs and awesome state park system Google Florida's springs.

Happy Green Roofing!


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