Invasive plants harm their host parks

In photos, they look like attractive plants you would find in a vase in your living room, but alligator weed, Brazilian pepper trees and water hyacinth are far from the typical house plant.

Alligator weed cause a threat to the economic and environmental states of parks internationally and nationally.

The problem has persisted so badly in places like Australia that $3 million has been spent in attempt to control the weed.

Click on the video at the right to view an audio slideshow about invasive plant species in national parks narrated and prepared by writer Jordan Emanuel. Photos courtesy of the National Park Service).

Alligator weed can be found in 27 states, including Florida, California, South Carolina and Georgia.

With the ability to grow in water and dry land, alligator weed covers water masses and blocks waterways and drains. The weed grows on top of water and prevents fish and other plants from getting proper oxygen and water regulation.

Not only do they live in various places, they can live when the sun is at full power or with very little sun at all. And though alligator weed can live in cold winters, the plant dies in freezing temperatures.

New plants grow quite quickly, forming from the stem and seeds.

“Alligator weed reproduces from roots and seeds so it grows very rapidly and spreads so quickly that it’s hard to maintain and get a handle on the issue,” said Dr. Michael Masser, associate department head and program leader, a professor and Extension Fisheries specialist at the Texas A&M System.

Because of human interaction these plants are spread quite frequently, also contributing to the problem.

An example of how alligator weeds dominant pond and lake surfaces. This makes it difficult for species living underneath to get oxygen (Photo courtesy of Chris Evans, River to River CWMA,

“They are mainly a problem in aquatic areas, it’s going to be an issue in areas that have recreational use like with boat ramps. Anywhere you are going to be putting something in water, taking them out, and moving them that’s how its spread through humans moving it around,” said Rebekah D. Wallace, data coordinator for the Center for Invasive Species and Ecosystem Health at the University of Georgia.

Another rapidly growing invasive plant is the Brazilian pepper tree.

“These peppers have the ability to reproduce and grow very densely and fast, which displace native species’ vegetation and habitats,” said Kenneth A. Langeland, Ph. D, Researcher Associated with the Center for Aquatic and Invasive Plants at the University of Florida.

With birds and other animals being the primary source of distribution, it is hard to get a handle on the spreading of this aggressive species.

“Birds eat it and spread it that way. There have even been studies that says that the invasive food source is of poor quality compared to what the native species usually eat,” said Wallace.

These trees not only alter the food quality of animals, but also create a dense shade that prevents sunlight from getting to plants and creatures that need it to survive.

At left, the vibrant color of these Brazilian pepper trees make it deceiving to those unaware of its destructive capabilities (Photo courtesy of Dan Clark, National Park Service, Below, a water hyacinth masking its danger to native species and their habitats with the soft lilac and luscious green leaves (Photo courtesy of AquaPlant, a Web site of AgraLife Extension, Texas A&M University System).

Brazilian pepper trees can grow over 30 feet tall and live for 30 years. These pepper trees can form from stems and seeds, which are viable up to two months.

Managing these trees has proved to be a difficult task due to the location of the trees.

“They reproduce very quickly and in such remote areas. It makes it hard to get to where they are,” said Langeland.

Complete elimination of the Brazilian pepper trees are unlikely, but there are ways to get rid of some of them.

“Eliminate is a strong word, but we manage them mainly with crews that apply herbicides some can be applied to bark and the tree will die in place or some cases the trees are cut and the herbicides are applied to the stomp or soil,” said Langeland.

Another invasive plant that is creating trouble in parks is the water hyacinth. This aquatic plant has made its home in the southern states.

The water hyacinth has light blue and purple flowers and deep green leaves. But do not let the attractiveness of it fool you.

This is an aggressive species that forms thick layers that can cover an entire pond or lake surface. Layers can grow as much as an acre and weigh 200 tons.

This invasive blanket of weeds can completely deprive fish from oxygen and sunlight, which kills them. The leaves also have the potential to clog waterways, which would prevent fishing and boating activities.

The water hyacinth is a pleasant site, which is why it does not get removed as it should. “It moves whenever we move. The water hyacinth is a pond plant and people don’t want to get rid of it because it’s pretty,” said Wallace.

So with a tendency to want to keep them around, how can this problem be managed? According to Wallace, education and incentive is the key.

“When focusing on education you have to figure out who your target audience and your approach to figure out how it would impact that group,” said Wallace. “It’s about stressing how you will impact them and what they will lose if it is not dealt with.”

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