water lettuce

WaterLine photo by Capt. Ralph Allen

Driving the boat across a weedy field? Nope — this is what Shell Creek looked like in August. All that green is water lettuce, a floating aquatic plant.

There’s been a lot of floating aquatic vegetation riding the current in the Peace River into Charlotte Harbor in recent weeks. The floating greenery has generated quite a bit of discussion about all the “hyacinths” in the river and in the Harbor this year, but the vast majority of the floating greenery has actually been water lettuce and not water hyacinth.

As these plants float out of the mouth of the Peace River and enter Charlotte Harbor, they begin to wilt, turn brownish in color, and die because they cannot survive in water that has a lot of salt. Usually by the time these plants reach the U.S. 41 bridges, they’ve begun turning brown.

During summers with lots of rain, more of these plants can be flushed down the river and they’ll survive further downstream. Summers with less rain typically see fewer plants and a quicker decay.

Both water lettuce and water hyacinth grow in the Peace River watershed. Both are long-established, exotic, invasive, fast-growing floating plants that can get carried into Charlotte Harbor during the rainy season.

Water hyacinths are a darker green color and include stalks which extend a foot or more above the surface of the water. Rafts of water lettuce are usually a lighter green color and generally don’t reach more than a couple of inches out of the water.

Both plants are native to South America and were somehow transplanted to Florida. Water hyacinths have been here a very long time, having been documented here since the 1880s. They may have been introduced in Florida intentionally as an ornamental pond plant, since they sprout beautiful clusters of lavender-colored blossoms.

Water lettuce (which, by the way, is not at all related to salad lettuce) has been here even longer, with reports dating way back into the 1700s. It’s more likely to have been brought accidentally somehow, though no one knows for sure how it arrived.

Both of these plants can cause a myriad of problems. Dense floating mats of interlocked plants can block sunlight from reaching native submerged aquatic vegetation. When the mats get really thick, boats can find navigation through them to be difficult or impossible.

When canals or drainage ditches are clogged with heavy growths of these plants, water flow can be impeded, leading to problems with flooding.

Yet another problem: When these plants die, they sink to the bottom and their decomposition robs oxygen out of the water which can kill fish and other aquatic creatures. The decomposition also dumps tons (literally) of nutrients into the water. These things cause a lot of grief.

For these reasons, Florida and the federal government have been attempting to manage the populations of water lettuce and water hyacinths for many years. This is sometimes done by mechanically harvesting the plants, but the primary method of control is spraying herbicides to kill them.

Controlling these plants is challenging because they are very widespread in Florida and because they have incredibly high growth rates. Water hyacinth populations can double in size in two weeks. Water lettuce is a comparative sluggard, since about the fastest it can grow is a doubling of population size in about three weeks, but both these plants are among the fastest growers on planet Earth. It is simply remarkable to watch how quickly either of them can completely cover a pond or other protected body of water.

I can remember back in the 1970s and ‘80s when we had huge clumps of water hyacinths in upper Charlotte Harbor every summer. Some of the rafts would be 100 feet or more across.

We used to fish for tripletail under hyacinth rafts because they’d hang beneath hunting for crabs, shrimp and small fish among the maze of down-hanging roots. Smaller clumps were better for tripletail fishing because we had no way to get a bait through the dense mats and could only fish around the edges.

I can also recall very large mats of water hyacinth being pulled into the mouths of some of the PGI canals by incoming tides, and jamming those canal mouths so tight that boats could not break through.

Some good news: Apparently the control measures that have been applied to water hyacinths during the last several decades have been effective in reducing the hyacinths in the Peace River basin, because in recent years it has been rare to see more than a few scattered clumps reaching Charlotte Harbor.

But there’s lots of water lettuce now. Much of the lettuce that’s currently coming into Charlotte Harbor is reaching the Peace River via Shell Creek. There has been a bumper crop of it in Shell Creek above the dam and up in Prairie Creek this summer.

Water lettuce and water hyacinths in those areas are usually sprayed with herbicides a few times per year to control their populations. But for some reason, there has not been much spraying done there for some time, and the population has really exploded.

As you might guess, the large-scale spraying of herbicides in the watershed is very controversial. There are all kinds of reasons to be concerned about the effect of chemicals on our waters and on the ecosystems that they harbor. And when the sprayed plants die they sink and decompose on the bottom, which can cause additional problems.

But these incredibly prolific floating invasive plants have the ability to completely choke out huge areas of fresh water by so blanketing the surface that native vegetation is physically crowded out or is blocked from receiving sunlight. Then when individual plants in huge, dense mats naturally die and sink, the amount of decomposing material can be much greater than if the plants had been sprayed and killed before the mats had a chance to become so huge.

So is it better to spray or not to spray? I don’t know the answer. It’s easy to be opposed to the application of any chemicals to our waters, but would the resulting explosion of non-native plants do more damage than the chemicals?

Unfortunately, as with most environmental issues, the solutions are not obvious, easy or cheap. Maybe we can figure out a way to make these plants commercially valuable. Salad, anyone?

Let’s go fishing!

Capt. Ralph Allen runs the King Fisher Fleet of sightseeing and fishing charter boats located at Fishermen’s Village in Punta Gorda. He is an award-winning outdoor writer and photographer, and is a past president of the Florida Outdoor Writers Association. Contact him at 941-639-2628 or Captain@KingFisherFleet.com.

Capt. Ralph Allen runs the King Fisher Fleet of sightseeing and fishing charter boats located at Fishermen’s Village in Punta Gorda. He is an award-winning outdoor writer and photographer, and is a past president of the Florida Outdoor Writers Association. Contact him at 941-639-2628 or Captain@KingFisherFleet.com.


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