Milfoil Species

Invasive aquatic plant species are a threat to the biodiversity of natural ecosystems, recreation and the economy in the Lakes Region. Because of the severe negative impact milfoil could have on the region’s greatest assets, 11 non-native milfoil species have been banned by the state of Maine.

These species include Brazilian elodea, curly-leaf pondweed, Eurasian water milfoil, European frogbit, European naiad, fanwort, hydrilla, parrot feather, variable-leaf water milfoil, water chestnut and yellow floating heart. Of these plants, the following five have been found in Maine waters:

Curly-leaf Pondweed

Native to Europe and Asia, curly-leaf pondweed was introduced to the United States in the mid 1800s. This type of pondweed will grow in both shallow and deep waters, and thrives on soft sediments. Its leaves are made distinct by their serrated and ruffled edges. Curly-leaf pondweed grows rapidly and as a result, can wipe out native species and reduce biodiversity.

Eurasian Milfoil

This type of invasive milfoil is considered the most threatening. Eurasian water milfoil was introduced to the United States in the 1940s, and has been confirmed in most states, including Maine. It is a particularly resilient plant, and extremely well adapted. Eurasian milfoil will quickly spread, and forms dense mats on surface waters. Unlike many other invasive aquatic plants, Eurasian milfoil often survives the winter, which also helps it to infest like no other.

As its name suggests, Eurasian milfoil is native to Europe and Asia. It has feather-like leaves, with typically 12 to 24 pairs of leaflets. In cases of massive infestation, Eurasian milfoil can make boating, swimming and fishing impossible.

Hydrilla

There are two types of Hydrilla found in the United States; monoecious and dioescious. Monoecious hydrilla grows in Maine and has male and female flower parts on the same plant. Its tiny leaves are strap-like and translucent. Hydrilla is native to Africa, Australia and parts of Asia, and is sometimes referred to as “the perfect weed” because of its ability to grow in a wide variety of conditions, including deep waters and currents.

Variable-leaf milfoil

Variable-leaf milfoil is responsible for most milfoil infestations in Maine. Though it is native to the United States as well as Europe, it is not native to Maine, or any New England state. Variable-leaf milfoil is highly adaptable, with the ability to grow in still and flowing waters, as well as to survive under ice. Also, its strong roots help it to survive through winter months.

Variable milfoil has thick stems and feathery leaves, which are arranged in densely packed whorls. Variable milfoil can be spread through seed or fragmentation, which is easily caused by boat propellers. Even a very small fragment of variable milfoil can cause an infestation. There are variable-leaf milfoil infestations in Sebago Lake, the Songo River, Brandy Pond, and the Presumpscot River.

Hybrid milfoil

Hybrid milfoil infestations have been found in Windham and Gray. This species is a cross between variable milfoil and another non-native milfoil. Hybrid may look like variable-leaf milfoil, with a distinguishing feature. For instance, the hybrid species found in Little Sebago Lake has a bright red stem. It is often very difficult to identify a hyrbid species, because appearence may vary widely.

Source: Maine Center for Invasive Aquatic Plants