SCHOHARIE COUNTY — A creeping invasion of Japanese knotweed, especially along local streams, is prompting area environmental officials charged with controlling erosion to ask for landowners’ help.

Originally imported about 100 years ago as an ornamental plant, Japanese knotweed is now crowding out more desireable wild plants throughout much of the Northeast, according to Peter Nichols, the stream program manager for the Schoharie County Soil and Water Conservation District.

“It’s something we’re seeing a lot in Schoharie County,” Nichols said. “It doesn't have a strong root system,” he said. When large colonies of the plant develop along stream banks they overwhelm native plants. And since they die back in winter, it doesn’t hold the soil or water back as well as native plants like sedges or dogwood, he said.

“It doesn’t do anything for streambank stability,” Nichols said, even while the plant itself can survive strong floods and keep regrowing.

As a result more silt is washed downstream in floods and stream banks erode, he said.

Over the summer, Nichols said he’s spotted big clumps of the tall plant with elongated heart-shaped leaves throughout the upper Schoharie Creek and its tributaries.

“It will completely take over a stream bank and eradicate what’s there,” he said.

Knotweed also likes disturbed soil and grows along roadsides or empty lots, where it’s sometimes brought in with dirt used for fill.

It’s popping up all over, with clumps of the 10-foot tall plants noticeable along the upper Cobleskill Creek near the Warnerville Cut-Off and by the Richmondville westbound exit of Interstate 88.

It’s also widespread along the Manor Kill in the Conesville area and other streams feeding into the Schoharie Reservoir.

New York City Department of Environmental Protection staff are also interested in eliminating the weed, according to Nichols, since stream erosion sends silt into the reservoir system.

Nichols said he’s also noticed knotweed along the East Branch of the Delaware River, another part of the city’s watershed in the Catskills.

The bamboolike stalks are easy to spot right now, with attractive clumps of tiny white flowers waving above the large, green leaves.

Getting rid of it is tough, however.

It can take three years of time-consuming vigilance, according to Nichols.

Cutting the plants down is only part of the process, since it can regenerate from even small pieces of its tough, tubular roots, called rhizones, that form a network under the plant colonies.

According to the Plant Conservation Alliance, advice on the National Park Services Web site, digging up the roots and runners is effective for small beginning populations of knotweed.

Once a colony is too widespread, however, “the best thing to do nothing,” Nichols said.

Early detection is what he’s hoping for, and “anglers are my eyes and ears,” he said.

Soil and Water Conservation District staff recommend cutting or mowing the plants to ground level every two or three weeks, until the plants die.

The next step is crucial, Nichols said. Cuttings should be allowed to dry completely on plastic or other impermeable material, then composted. If feasible, green plants may be burned or buried 10 feet deep, he said.

Digging such a deep hole is not something most people will likely do, Nichols acknowledged. The burning option is also problematic, especially since the state Department of Environmental Conservation is proposing more limits or bans on outdoor burning.

Herbicides, such as Roundup, are also sometimes injected directly into the plants to kill them, Nichols said. For more information, Nichols may be called at 234-4092.