LEYDEN — The Conservation Commission and Highway Department have crafted a proposal, expected to cost $2,621.52, to curb the growth of Japanese knotweed in town.

The plant has colonized large stretches of roadside areas in Leyden and surrounding communities over the past decade, according to the proposal, and “if left unmanaged ... these colonies threaten to block driver and pedestrian visibility as well as vehicular traffic.”

Additionally, Japanese knotweed can impede water flow and lead to an increased risk of flooding — a problem that will likely be exacerbated by the more powerful and frequent storms that result from climate change. Another concern is when the plant is near man-made structures like bridges, roads, sidewalks, parking lots and foundations, the rhizome (a continuously growing underground stem) can split structures at their weakest points.

During a recent Conservation Commission meeting, members reviewed the budget and requested $2,621.52 from the Finance Committee for removal. Commission Chair Evan Abramson wrote in an email that he expects to hear from the Finance Committee by late February or early March.

Costs related to knotweed removal are as follows:

■$306 for work by the Highway Department, plus $135.52 in material costs (including gallons of fuel).

■$450 to capture GPS coordinates of where the knotweed is growing, and to take note of the size of the plant, the land use and the proximity of the plant to wetlands.

■$400 to import the GPS points generate a map and datasets of the knotweed locations in town.

■$650 to analyze the data on a map and categorize each of the knotweed locations based on site conditions and proximity to wetlands.

■$272 to review the recommended knotweed removal methods for each location.

■$408 to develop a budget for the knotweed control on all of Leyden’s roads based on the recommended methods for each location.

Abramson said the Conservation Commission hopes to “continue targeting and removing the knotweed by the middle of the summer this year (or) at the latest starting spring of next year.”

The commission hopes to use a non-chemical approach called smothering, which was used in a trial on North County Road last summer. According to the proposal, smothering causes no soil disturbance or erosion issues. The Japanese knotweed stems would be cut and then layered with 3 to 4 inches of bark mulch or wood chips that would act as a cushion layer. On top of the first layer would be 7 millimeters of black plastic or non-woven geotextile anterior. The last layer would be another 3 to 4 inches of bark mulch or wood chips.

Abramson said herbicides are another option, but this proposal would be discussed during a future meeting.

“By the time this money is awarded, we’ll have a better idea of what sort of competing strategies are feasible,” Abramson said during the most recent Conservation Commission meeting. “We’re just gathering more and more information so that when we do get the funding to actually do something, we’ll have … the right approach, and we won’t waste the money. … But unfortunately, this is occurring across the state and across the region.”

An earlier version of this article included a photograph that incorrectly identified Japanese knotweed.

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