Melaleuca Lockdown In Loxahatchee

The Loxahatchee Slough Natural Area is a 12,000-acre mosaic of wetlands, pine flatwoods, cypress swamps and wet prairies on the northeastern edge of the Everglades in Palm Beach County, Fla. It provides the largest area of habitat for threatened Florida sandhill cranes and other wading birds. Endangered snail kites and wood storks also call the Slough home, along with many other threatened species of birds and reptiles.

This exceedingly rare ecosystem is threatened by the spread of melaleuca — an invasive tree species that grows up to 80 feet tall, creating a dense monoculture that has overtaken wildlife habitat and altered water flow through the region.

An Ecosystem Interrupted

From the laundry list of mini-ecosystems interspersed throughout the Everglades, it might seem there is room for virtually any plant. But according to Todd Olson of Aquatic Vegetation Control, Inc. (AVC), there is no room for invasive species like melaleuca.

"Melaleuca in particular is a problem species in the Slough. The root systems in melaleuca monocultures can quickly create dry land in knee-deep water," he said. "This disrupts the overall hydrology by changing the way the sheet of water moves through the slough."

Pitching In For the Long Haul

Frank Griffiths is the leader of the Palm Beach County team fighting to protect the Slough. He and other members of the Palm Beach County Department of Environmental Resource Management developed a five-year restoration plan that includes removal of 780 acres of melaleuca and other invasive plants.

"We have two primary goals for the restoration of the Slough," said Griffiths. "We want to reintroduce fire into the ecosystem to help native plants thrive, and we need to control and remove invasive species from the area."

One important partner in the plan is Olson and his team from AVC. Griffiths chose AVC partly because of its standing as a Quality Vegetation Management™ (QVM) Certified Applicator.

Vegetation management professionals who are QVM Certified strive to go above and beyond in their duties as vegetation managers to restore and improve habitat while protecting threatened and endangered species. They also engage in advanced technical training to ensure they are applying herbicides responsibly, in a way that benefits the environment being treated.

AVC has developed creative strategies to access some of the more remote areas of the Slough. Merely reaching stands of melaleuca in these remote areas can be as challenging as keeping the plants under control. "Over the course of the restoration program, we've had to fly crews into treatment sites on more than one occasion," said Olson. "In other cases, prescribed burns have helped us gain access to remote areas that were otherwise inaccessible."

Choose Your Weapon

According to Olson, much of what determines the control method relates to the melaleuca tree diameter and whether an infestation has completely taken hold. In areas with only a sparse population of seedlings, hand-pulling is an option for control. But as the monoculture fills in and grows tall, spraying melaleuca is the best first step.

"If the trees are greater than four inches in DBH [diameter at breast height], we use a frill and girdle technique to treat melaleuca," said Olson. "We remove the paper bark to expose the cambium in a three to five-inch band around the tree, and treat the exposed area with a Habitat® herbicide solution with MSO [methylated seed oil]."

For areas where trees are less than four inches DBH, cut-stump treatments using the same amount of Habitat can be used. Vast monocultures may be treated with a helicopter foliar application of Habitat and Rodeo®, plus a surfactant.

Treatments are completed in a "target" pattern, moving from the outer edges of infestation to the inner cores. This method cuts off further expansion, and creates a trackable pattern for future treatments.

Holding the Line

A one-time spray treatment will not eliminate a stand of melaleuca. It takes several seasons of working a comprehensive plan to get the job done.

"After the first spray, melaleuca releases millions of seeds, and getting the mature trees out of the way actually gives the seedlings more of what they need to flourish," said Griffiths. "We maintain all the outlying areas in the target pattern as we work inward, so treatments are cumulative."

Treatments include mechanical removal of the largest tree skeletons and/or chipping tree litter in the densest monoculture areas.

Until the trees have been removed, prescribed burning isn't an effective tool for Slough management. Melaleuca is well adapted to fire; it burns extremely hot and adult trees typically are only charred. This means the adult trees have an opportunity to reseed before native plants, which are often destroyed by the hotter fires fueled by the large trees.

However, after the areas are opened, prescribed burning can be effective. When conducted properly, the fires burn off competing vegetation and encourage new growth that wildlife can use for food.

"When it comes to restoration in the Loxahatchee Slough, we're in it for the long haul," said Griffiths. "Working with great herbicide applicators like AVC and following our long-term plan can make a real difference for endangered wildlife and our diverse ecosystem."