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Could floating flower gardens be an answer to Miami’s polluted canals?

The flowers roots grow out of the holes in the mat into the water and suck up the phosphorus and nitrogen.
Margi Rentis
The flowers roots grow out of the holes in the mat into the water and suck up the phosphorus and nitrogen.

Miami-Dade’s canals aren’t exactly scenic. More often than not they’re full of discarded tires and plastic bags — and so polluted from fertilizer runoff, dog poop and sewage leaks that experts frequently warn you shouldn’t swim in them.

But what if the canals were beautified and cleaned up using garden beds of yellow and orange sunflowers, marigolds and fluffy and colorful celosia instead? That’s exactly what Florida International University researchers are trying to do, and so far their tests have shown promising results.

“We saw that the bigger the plants grew, the more clean the water got,” Jazmin Locke-Rodriguez, a postdoctoral associate at the Institute of Environment at FIU said. “And we think our research is absolutely scalable.”

READ MORE: The journey of Valentine's Day flowers to the U.S. begins in South America and goes through Miami

Wetlands are a defining feature of South Florida’s ecosystem in the Everglades, and free-floating native plants like duckweed and water hyacinth filter out the nitrogen and supply oxygen to the water. But as wetlands disappear due to development, one of the Earth’s best natural cleaners goes with it, Locke-Rodriguez said.

Scientists across the globe have been experimenting with “floating wetlands,” man-made rafts housing native plants that improve the water quality and help restore life to the ecosystem. In Central Florida, the state and federal government have poured millions into stormwater treatment areas, wide swaths of submerged plants that clean the dirty water flowing off Lake Okeechobee.

Researchers say these nature-based solutions are necessary, especially as climate change is warming the water. When storms happen, the water that passes through farms and yards catches the poop and fertilizer and whatever else and brings it into the canal. This can cause algae blooms, which can then cause fish kills. Make it hotter, which climate change is doing, and there are even worse effects.

“As we are dealing with climate change, the pollutants are getting into the waterways. These floating devices meet all ecological, environmental and economic ways of treating the problem sustainably,” said Krish Jayachandran, and FIU professor of Agroecology the project’s advisor.

Marigolds growing in a test pool at FIU.
Margi Rentis
Contributed to the Herald
Marigolds growing in a test pool at FIU.

While valuable, it’s important to maintain the floating wetlands for them to hold on to that value. Most of the man-made floaters use wetland plants, and research has found that they need to be routinely harvested or the plants die off, fall in the water, and rot — returning all the nutrients they sucked up back to where they got it.

But unlike Everglades stormwater treatment areas, this team has a novel use for the harvested plants: sell them.

“If it’s important to harvest these plants regularly, and obviously it can be labor intensive. Why don’t we make use of the harvest? Which caused me to look for things that have value to grow,” Locke-Rodriguez said.

So that’s why they chose to grow what looks like Easter flowers you’d see fresh cut at a flower market stand. If it all goes to plan, their project wouldn’t only pay for itself but be a part of a profit-making business in the largest import city of ornamental flowers in the world.

“Miami is the place for the flower industry, and year-round we can grow these and make an income,” Jayachandran said.

Locke-Rodriguez founded a start-up with this idea in mind called Green Thumb Strategies: PhytoFlora which has support from the entrepreneur non-profit, the SeaWorthy Collective. Their idea was inspired by floating farm practices like the Aztecs’ chinampas in Mexico and the Miccosukee tree island settlements in Florida.

The in-field test site was set up for 10 months in the canals. The flowers were first grown in a nursery and then transferred on a buoyant mat platform called a Beemat. The Beemat has rows of planting holes and the plant’s roots protrude out the bottom; long, clumped and stringy like moss.

“That team can grow as we grow, which I also think is an exciting opportunity to create green jobs,” Locke-Rodriguez said.

Jazmin Locke-Rodriguez
The Miami Herald
Jazmin Locke-Rodriguez

More testing to do

There is still a winding path ahead in determining the best flowers and floating platforms to use and getting county support to employ them. And there are still some kinks the team is trying to work out too.

For instance, finding the right spot for the project.

The team found that the Coral Gables canal was too salty for the flowers to grow. And in the Little River canal, where the researchers did find some fresh water, iguanas took their petals as a tasty snack before the flowers could fully bloom — so they might try adding a net of sorts next time.

Locke-Rodriguez said they are also looking for more natural materials to plant the flowers in that don’t involve a plastic mat. While research shows the mat should hold up for 10 years and be recyclable, some people have questions and concerns about the plastic leaching.

In the first round of tests, African Marigolds cleaned the water best. The marigolds cleaned 52% more phosphorus and 36% more nitrogen than what would be removed if left up to the slow-moving natural process of nutrient removal. But in subsequent tests the team hasn’t published yet, the sunflowers and celosia showed similar if not better results, Locke-Rodriguez said.

They aren’t exactly sure why the marigolds performed so well, but they have some guesses. For one, marigolds grow roots from their stems too, which helps stabilize them and could possibly mean increased nutrient consumption.

Locke-Rodriguez said they would plant their nursery-grown flowers in the waterways according to the seasons because the plants consume more nutrients the bigger they get. When it’s rainy season and run-off is at its peak, they want the flowers to be at their peak of growth too.

“Think about it, babies eat a little bit, and when they get bigger and are teenagers they’re at their peak eating the most, and once they stop blooming, they taper off,” Locke-Rodriguez said. “It’s the same with flowers.”

In those first four to six weeks while the plants are getting acquainted with their space and starting to grow, they don’t need as much attention. But in theory, they’d be able to go out once a week to harvest the flowers to sell.

“We have the protocol, hopefully now Miami-Dade county will say ‘yes let’s do this.’” Jayachandran said. “We are looking forward to a community approach to get this going.”

Ashley Miznazi is a climate change reporter for the Miami Herald funded by the Lynn and Louis Wolfson II Family Foundation in partnership with Journalism Funding Partners.

This story was produced in partnership with the Florida Climate Reporting Network, a multi-newsroom initiative founded by the Miami Herald, the South Florida Sun Sentinel, The Palm Beach Post, the Orlando Sentinel, WLRN Public Media and the Tampa Bay Times.

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