The Longyandong farm in south China's Guangdong Province is not the only place that has suffered from an invasion of Merremia boisiana.

In a news bulletin in July, the United Nations Development Program (UNDP) in Viet Nam reported that some 1,000 hectares of special use forest in Viet Nam's Da Nang Province "are severely overgrown by an unidentified invasive liana species."

Tran Huy Do, director of Nam Hai Van special use forest, told the UNDP officials that the plant has been rapidly spreading across pine and acacia forests since 1999.

"The resulting dense canopy is killing the trees and plants in the forest below by starving them of sunlight," the news bulletin stated.

Local researchers from Da Nang Forest Protection Department (FPD) surveyed the damaged forest and identified the invading plants as two types of bindweed - Merremia boisiana as well as Ipomona eberhardtii.

The researchers warned that "the presence of the plants also heightens the risk of forest fires as the large, thick leaves catch fire easily, even when green.

In fact, Nguyen Manh Tien, head of the Forest Management Section of Da Nang FPD, said there had already been nine forest fires in Da Nang by July, "mostly in areas where the invasive bindweed species are present."

Between 2000 and 2001, the local Da Nang authorities mobilized local efforts and money to chop down, dig up or burn the plant to stop the two species of bindweed from spreading to other areas.

"However, this is not a long term solution," the bulletin stated.

Twinners and climbers

According to Daniel F. Austin, from the Conservation and Science Department of the Arizona-Sonora Desert Museum in the United States, Merremia boisiana and Ipomona eberhardtii are among the family of the Convolvulaceae plants.

This family of plants "is dominated by twining or climbing woody or herbaceous plants that often have heart-shaped leaves and funnel-shaped flowers," Austin wrote in his special web page on Convolvulaceae.

According to Austin, this family of plants, most of them commonly known as morning glories, are distributed in the tropics of the world, although, he pointed out, some species also reach temperate zones.

The greatest species diversity occurs in the Americas and Africa. About 10 genera are endemic to Asia. However, he wrote, Bonamia, Ipomoea, Merremia, and Operculina are distributed throughout the tropics.

According to the United States Department of Agriculture (USDA), people in North America usually know only the weedy species of the Convolvulaceae.

In fact, because some of the bindweeds cause heavy annual losses to agriculture and home gardeners, the USDA has listed the two species on the US Federal Noxious Weed List.

These two are what the local Americans call "little bell" (Ipomoea triloba) and "water spinach" (Ipomoea aquatica).

Meanwhile, the USDA has developed a list of invasive plants, recognizing the fact that these plants are "invasive or have a high potential to become invasive in all or part of their US range."

On the list is Merremia tuberosa Rendle, or woodrose/Spanish arborvine, which belongs to the family of Convolvulaceae or the family of morning glory.

The image of Merremia tuberose from the Internet has a strong resemblance to the Jinzhongteng, or Merremia boisiana.