"Good plants gone bad" is how an LSU AgCenter urban forester describes plants that have invaded the Louisiana landscape and created problems for farmers, forest owners and homeowners.
Dr. Hallie Dozier, an assistant professor in the School of Renewable Natural Re-sources, says the introduction of foreign plants often causes problems because they don't have natural enemies to control their spread.
|
Advertisement |
"Things that make a good ornamental plant make a good invader," Dozier said. "It flowers and fruits a lot and produces lots of seeds."
Flowering plants are attractive to pollinators - primarily honeybees - and to "dispersers" - primarily birds, she said. "So people who like bees and birds in their yards like these plants."
In addition to flowering profusely and producing seeds, other characteristics of invasive plants include the ability to thrive under a wide variety of growing conditions and tolerate significant aboveground damage.
Invasive plants can cost agricultural producers and land owners tens of millions of dollars for weeding, herbicides and research to control them, Dozier said.
In natural, uncultivated areas, these plants can be equally challenging, she said. Left unchecked, the Chinese tallow tree can transform woodland ecology, change the hydrology and even affect the microclimate where they grow.
For example, after Chin-ese tallow trees began growing in wet prairie soils in Southeast Louisiana, the environment was transformed to woods, changing the ecosystem. "That chan-ged all the rules for all the animals," Dozier said.
Dozier said insect and disease resistance are common among invasive spe-cies. These traits not only make them hardy in the wild but also allow them to thrive in cultivated locations.
Kudzu was introduced for erosion control in Southern landscapes that had been denuded as a result of railroad expansion in the late 19th century. Now, kudzu engulfs almost anything in its vicinity, growing as much as a foot a day under the right conditions.
Other common attributes of invasive plants include being evergreen, so they grow through winter; not being picky about light or soil conditions, so they grow almost anywhere; and fast-growing, so they're difficult to manage. In addition, many also reproduce asexually - through rhizomes and underground roots - so they can be spread by cuttings as well as by seed.
Invasive species provide competition for tree growth in Louisiana forests, and some species, such as Chinese tallow, get in the way because loggers won't harvest it, said Bill Gall-agher with GR Forestry Inc. in Amite.
Gallagher said he has seen privet as tall as 30 feet in streamside management zones.
"You could ride a horse under it," he said. "The canopy is so dense nothing can grow under it."
Gallagher estimates that without good site preparation, a tree stand could be as much as a third less in value after 30 years because of invasive plants.
Cogon grass is a recently introduced species becoming a problem in Louisiana, primarily in the Florida parishes, where conditions are conducive for its growth, Dozier said. It's moving west from Florida and Alabama, where it was introduced as forage for grazing cattle.
"Unfortunately, it's only good for grazing when it's small," Dozier said. "When it grows taller than a few inches, it becomes rough and unpalatable because of silica in its leaves."
Experts believe cogon grass has been moved mostly by the tires of heavy equipment working in pipe-line and power line rights-of-way. The plant reproduces by rhizomes as well as seeds, so small clumps can be moved unintentionally on vehicles and grow where they're dropped.
"Cogon grass is in the top 10 worst weeds in the world," Dozier said. "World-wide it costs farmers a lot and causes ecological damage in woodlands - pine forests in particular."
Cogon grass is starting to appear as a forest problem in Louisiana, mostly in power line and pipeline rights of way, said Cal Baker of the U.S. Forest Service in Pineville. The grass takes over a site and chokes off the forest floor, eliminating habitat for wildlife.
"It's now taking off in Louisiana," said Baker, who's on the ecosystem conservation staff in the Kisatchie National Forest.
He said he's seen patches of cogon grass south of Leesville near Colfax and is concerned about its effects on forestlands. The grass forms a dense mat about a foot high and has a high silica content.
"It crowds out every other species and competes with establishing trees," Baker said. "It's a struggle to get other species back in the ground."
Baker said the Forest Service is trying to keep the invasive grass out of the forest by monitoring and using herbicides before it gets out of hand.
Baker said kudzu and trifoliate orange are other invasive species that trouble forests in central Louisiana. And privets are "just everywhere," he said. "Controll-ing them is like swatting mosquitoes."
Baker also said Japanese climbing fern, Chinese tallow trees and mimosa trees are problems.
"With kudzu, we still have the ability to control it with early identification," he said.
Baker said controlling invasive plants requires a collaborative approach among all concerned.
Information provided by LSU AgCenter.
Comments