The plant is bright green and bushy like a squirrel’s tail. Once it gets into a lake or pond, it can grow 15 feet tall, spread across acres and choke out all other plant and animal life.

It’s called milfoil. And a year after the invasive species spread to three more New Hampshire water bodies, lawmakers are considering a bill that fines those who negligently transport the plant, and other invasive species, to the state’s lakes and ponds.

“This is a serious, serious problem,” said Senate Majority Leader Jeb Bradley during recent debate on the policy. “If we allow milfoil to get into our lakes . . . we hurt people’s property values; we hurt tourism in New Hampshire.”

Milfoil was first found in Lake Winnipesaukee during the 1960s, and has since spread to more than 70 New Hampshire water bodies, according to the state Department of Environmental Services. Last year alone it cropped up in Turee Pond in Bow, Oxbow Pond in Canterbury and Pine Island Pond in Manchester. Officials say milfoil is mostly transported by people who get the plant stuck to their boats or trailers, and then carry it from lake to lake.

The plant’s spread is especially concerning to tourism officials because milfoil grows in the shallows, close to shore, where people like to swim, boat and fish.

While mitigation efforts can slow and sometimes stop the plant’s proliferation, it’s costly. The state spent roughly $1.1 million last year controlling the spread of milfoil and other invasive species, up from roughly $900,000 during the previous year, according to Amy Smagula of DES.

Towns and cities also chip in, and some dedicate thousands of dollars to mitigation efforts at town meeting each year.

The Northwood Lake Watershed Association plans to spend roughly $50,000 controlling milfoil this year through chemical treatments and suction removal, where divers rip it out at its roots. The towns of Deerfield, Epsom and Northwood all contributed between $3,500 and $10,000 to the mitigation effort this year alone.

Milfoil has taken over roughly 60 acres of the 650- acre Northwood Lake.

“It never goes away,” said Kevin Ash, president of the nonprofit Northwood Lake Watershed Association. “Once it’s in, it’s in. It’s all a matter of control after that. It’s getting it to a management level each year.”

The legislation would fine people who negligently transport invasive species, including milfoil, among New Hampshire water bodies. The first offense would result in a $50 fine, the second a $100 fine and the third a $250 fine.

The House and Senate passed different versions of the bill, and must agree on one.

Lawmakers hope the policy acts as a deterrent and helps to limit the spread of milfoil to New Hampshire’s 950 lakes and ponds and 13,000 miles of rivers and streams.

While milfoil represents one of the biggest threats to the state, other invasive species are also moving into water bodies here.

The Asian clam, yellow in color and roughly the size of a quarter, has already colonized four state water bodies including the Merrimack River. The clams disrupt the local ecosystem, and can pose a threat to swimmers, who run the risk of cutting themselves on the clams’ sharp shells.

New Hampshire is bracing for the introduction of hydrilla – an invasive water plant that can grow nearly twice the height of milfoil.

To prevent the spread of such species, officials recommend boaters inspect their boats for plants when they pull them out of the water, and then drain and dry them before launching into another lake or pond.

“The threat is real in terms of spread,” Smagula said. “By having statutes that can give us a little bit of teeth, hopefully it’s a disincentive to people who aren’t inspecting their boat or trailer.”

(Allie Morris can be reached at 369-3307 or at amorris@cmonitor.com.)