Rain gardens for Florida

Florida's 5-month wet season produces
50% to 70% of annual rainfall. (Data from NOAA)
by Ginny Stibolt

Too much rain or not enough

Florida's 5-month wet season (aka hurricane season), from June through October, accounts for almost 2/3 of our rainfall. In general, the more southern counties experience the more dramatic differences between their wet and dry seasons. In contrast, New York City's rainfall is more evenly distributed from about 3.5" to 4.5" each month.

Our weird patterns of rainfall help make the case for using Florida's native plants in our landscapes. Also we receive huge amounts of rain all at once on a regular basis. In most cases, all that excess water is rushed from our properties out to the streets where our stormwater then ends up in the nearest waterway. At that point it's no longer just water, but it will have collected pollutants from our landscapes and the streets. This is called nonpoint source pollution, which is not regulated and not monitored.

Nonpoint source pollution (NPS)

In addition to rainfall, over-irrigation is a common cause of NPS in Florida.
Rainbows of pollution headed toward the nearest
body of water.
Some people think that NPS is the most significant cause of water quality deterioration because it cannot be monitored effectively. This may be true, but I think that we can make a difference by sequestering as much rain water as possible through the use of rain barrels, cisterns, and rain gardens. We can reach out to others to help them do the same.

The EPA webpages on NPS include definitions, solutions, success stories, outreach tools, information about grants, and events. One of the solutions that homeowners and communities can implement is rain gardens.

Rain gardens

The downspout delivered water to the lawn, which became
a muddy, soggy mess throughout the wet season.
Because of Florida's long dry season, the selection of plants that can withstand both flooding and drought are quite limited. For instance, suggested rain garden plants for the Mid-Atlantic states and northward, often include the cardinal flower (Lobelia cardinalis), but it won't work for Florida's rain gardens, even though it's native down through Central Florida, because it is not drought-tolerant.

Rain gardens can be small like this downspout garden, which was expanded over a few years. First, I took out a few feet of lawn and created a small dry well by digging an 18" cube under where the tray dumps the water and filling it with coarse gravel topped in with some fake river rock  I planted some blue eyed grass, soft rush, and some ferns in the area. A couple of years later I expanded it by digging a good sized swale beyond the original dry well and overflow drainage through a French drain to a larger dry well near our front pond.. You can see details of this effort in this series of posts.
After a couple of expansions, this downspout rain gardens
 can handle any amount of rain.

Rain gardens can be large community projects which are designed to absorb all the runoff from parking lots or roads. The Lasalle Bioswale Project in Jacksonville is a good example of how various members of the community came together to build a highly visible rain garden to handle the stormwater runoff beautifully.

A likely spot for some rain garden plants to better absorb the parking lot runoff. At this point the lawn maintenance is skinning the roots of the trees, but groupings of good rain garden plants such as rushes, sedges, shrubs would do a better job of absorbing the water. 

White-topped sedge (Rhynchospora colorata) is a beautiful addition to rain gardens.

The 2016 FNPS conference

The 2016 FNPS conference will be in Daytona Beach.
I will be giving a presentation on rain gardens at the FNPS conference in Daytona Beach on Saturday May 21. I will provide details on siting and sizing rain gardens, a plant list for Florida rain gardens, and ideas for community rain garden projects.

After my talk I'll walk through the native plant vendors to talk in more detail about good rain garden plants and rain garden designs.

In addition, University Press of Florida will be a vendor for the conference and I'll be signing books during the lunch breaks on Friday and Saturday. I've dedicated whole chapters to rain gardens and rain barrels in "Sustainable Gardening for Florida," which include even more details and ideas for sequestering rain water on your property.

We all live in a watershed!

Ginny Stibolt


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