European Naiad

Seven years ago a snorkeler swimming on Milton Three Ponds noticed a weed he was not familiar with. For the past six years, TPPA, NH DES, ME DEP and the Towns of Milton, NH and Lebanon ME have been trying to control and eradicate an invasive aquatic plant known as European Naiad (Najas minor), also known as Brittle Waternymph, and Brittle Naiad.

European Naiad (EN) is native to Europe, western Asia and northern Africa. It’s unclear how it was introduced into the United States in the early 1930’s. It is a rooted, submersed aquatic plant. It is a true annual, reproducing primarily by seeds and secondarily by fragments. It starts growing in late spring and early summer. Although its growth is usually compact and bushy, the highly branched lime green stems can grow up to 2.5 meters tall. Unlike native naiads on Milton Three Ponds, the “toothed” or serrations on EN are visible without magnification.

EN grows and reproduces rapidly, and often displaces native species, reduces biodiversity and hampers recreational use. For these reasons, TPPA has utilized a combination of control measures. These include manual harvesting by trained Volunteer Invasive Plant Surveyors (VIPS), Diver Assisted Suction Harvesting (DASH) and treatments using a contact herbicide.

People spread EN primarily through the movement of motorized and non-motorized watercraft in late summer when the plant has produced seeds and becomes brittle. Seeds and fragments can cling to boats, gear and wildlife. Everyone should clean their watercraft thoroughly upon entering and leaving Milton Three Ponds. In 2021, total expenditures for controlling EN exceeded $55,000. The plant responded well to herbicide treatment on August 19th to several areas of the Three Ponds and to five weeks of DASH. EN is arguably one of the most difficult invasive plants to control in Maine and New Hampshire. In 2022 TPPA estimates control efforts will approach $80,000. Please support TPPA’s efforts and become informed about protecting Milton Three Ponds.

The table below details New England Milfoil’s (NEM) effort to remove European Naiad from Milton Three Ponds during the summer of 2021. TPPA has contracted with NEM for five weeks of survey and DASH (Diver Assisted Suction Harvesting) for 2022.

New Hampshire Department of Environmental Service has crafted a Long Term Brittle Naiad (aka European Naiad) Management Plan. The document is long but has excellent information about out battle with this invasive plant.