Easily Overlooked, ‘Minor’ Invasive Plants Also A Big Problem

November 12, 1999

GAINESVILLE — With its deep green leaves and small blooms, white-flowered wandering jew is an attractive ground cover often seen in yards throughout Florida.

But the Tradescantia fluminensis, a native of South America, is one of many exotic ornamental plants grown in homes or yards that are slowly crowding out the state’s native plant species, University of Florida researchers say. The plants themselves do not pose the threat of such abundant and well-known exotic species as melaleuca or hydrilla, but their combined impact on Florida’s native ecosystem is far more substantial than commonly perceived, the researchers say.

“Wandering jew isn’t going to take over the Everglades, but it is a problem in some habitats such as river flood plains,” said Ken Langeland, a professor of agronomy in the Center for Aquatic and Invasive Plants in UF’s Institute of Food and Agricultural Sciences. “You add more and more plants like wandering jew, and a bunch of small problems end up as one big problem.”

Florida is second only to Hawaii as the state with the most invasive plants, Langeland said. The reasons span the state’s mild climate, which allows many different kinds of plants to flourish, to Florida’s status of as a world plant shipment hub, he said. Eighty-five percent of plant shipments to the United States from other parts of the world come through Miami International Airport, he said.

Nearly half of the non-native plants found in Florida were brought in as ornamentals, with the bulk of the others introduced accidentally, as forage crops, or for other agricultural purposes, said Don Schmitz, a biologist with the Florida Department of Environmental Protection’s Bureau of Invasive Plant Management. Langeland said non-native species comprise 1,180 of the 3,834 plant species in Florida, though most are not considered invasive.

Brett McMillan, a UF botany student who will earn his master’s degree in December, probed the impact of wandering jew for his recently completed thesis. He found the plant “significantly reduced” the size of hammock grass, a native plant, when the two species are placed together in pots. He also found removing wandering jew from creek banks and forests around Gainesville brought back the nearly vanquished native species.

“After a year of keeping wandering jew out, I found that the native plants’ size and diversity increased a lot,” he said.

There are numerous similar low-profile invasive species found throughout Florida, Langeland said. They include wedelia, a ground cover with a small yellow flower; coral ardesia, characterized by its bright red berries; and heavenly bamboo, an evergreen shrub, he said.

Although many invasive plants are cultivated outdoors as yard ornamentals, even some indoor plants can become a problem, McMillan said.

“People dump the pots out in their back yard and the plants take off,” he said.

Langeland said it’s difficult to quantify the impact of invasive plants, particularly the less common ones such as wandering jew. But, as has happened with other exotics such as melaleuca, what may appear to be minor infestations today could be major ones in the future, he said.

“The typical population dynamics is that an introduced species will kind of hang around at low population levels and then, all of a sudden, it will go into a logarithmic expansion,” he said. “The process can take up to several decades.”

Schmitz said homeowners can help combat invasive species by choosing native plants when landscaping. The Florida Exotic Pest Plant Council, a private, nonprofit group that combats invasive species, publishes a list of plants it considers to be most invasive in Florida. The list can be found online athttp://www.fleppc.org/.