NORTH ATTLEBORO - The town may need to consider treating shoreline weeds at Falls Pond this summer to keep invasive species at bay.

The conservation commission received its annual report on the state of the ponds from biologists on Tuesday. Biologists who inspected Falls and Whiting's ponds last summer said both are in fairly good shape regarding submerged weeds, but shoreline weeds may be a concern.

The two culprits are phragmites and purple loosestrife.

Phragmites, also known as the common reed, is a grass that can grow up to 16 feet tall. It has been spreading rapidly over the past 50 years and grows aggressively enough that it crowds out other native species in wetlands.

Purple loosestrife is also becoming increasingly common along Massachusetts shorelines and can grow up to 9 feet tall with small purple flowers. Lower Falls Pond has scattered areas of purple loosestrife, Japanese knotweed, an invasive species with tiny clusters of white flowers, and one small area of phragmites. Because the infestations are intermittent, the town may want to use herbicides to keep the plants from getting a greater hold on the pond, biologists said.

Submerged weeds in upper Falls Pond are minimal because the pond is so deep. However, there is some evidence of bushy pond weed and milfoil in some of the shallower areas.

In Whiting's Pond, there isn't much evidence of submerged vegetation, except around the coves. However, there is a "problematic" amount of purple loosestrife and phragmites ringing the pond.

"It's 10 feet deep and 15 feet high around the majority of the pond," biologist Michael Lennon said.

"Treating it would be a much larger undertaking. It's probably at the point where it's not going to expand any more. The place you can make some headway is at Falls Pond because it's so patchy there."

Any treatment for those shoreline weeds would likely occur in August or September.