Invasive Species of Concern
Invasive species are plants, animals and insects that are "not from here" and evolved in a different environment. They can also be referred to as exotic, and non-native. Once established, they often find a niche and out-compete natural vegetation or animals. They take over quickly and can be quite destructive. Below are some invasive species in which the Department of Natural Resources is interested.
BUGS IN THE FOREST
Emerald Ash Borer (EAB)
Emerald Ash Borer (EAB) is an invasive insect that can kill an ash tree within 2-3 weeks. It is most often moved around by people transporting firewood, which is why it is very important to buy firewood near the place where you are camping or recreating. Currently, the nearest known outbreak is in Concord, New Hampshire. The EAB attacks any species of ash, including brown ash, which is a culturally significant tree species to tribes in the Northeast.
Currently, members of the Penobscot Nation DNR staff are working with the USDA-APHIS Program to monitor for the presence of EAB throughout the State of Maine and develop a plan of action to be implemented once EAB arrives in our region.
Click here for more information on Emerald Ash Borer.
Hemlock Wooly Adelgid (HWA)
Hemlock Wooly Adelgid (HWA) is another invasive insect of significant importance to the Penobscots’. Individually, adelgids are very tiny but clump together and look like small cotton balls. They are found on the underside of hemlock needles and effect only hemlocks. Identification is easiest during November – July.
HWA is currently found in southern and coastal Maine. The Atlantic Ocean is said to be a great transportation route since birds can transport HWA. Another way HWA is transported is through hemlock trees that people buy at greenhouses or plant nurseries. One plant in the nursery can infect others and when the tree is brought to the homeowner's property it can spread to hemlocks there as well.
Click here for more information on Hemlock Wooly Adelgid.
PLANTS ON THE LAND/NEAR WATER
Purple loosestrife is an invasive plant with a distinct square woody stem and purple flower. It is rarely found on trust lands, but is established on Indian Island along the boardwalk, pond and various drainage ditches. This plant has the potential to out-compete native vegetation in wetlands and significantly limit diversity of plants and wildlife. Large populations of loosestrife are extremely difficult (if not impossible) to control for Natural Area Managers. Hand pulling or digging up plants is only successful when the small plants are newly established. It must be done thoroughly and at the right time of year so seeds are not being spread during the pulling. This method has worked well on the PIN trust lands. Please contact the DNR forestry program for input on how to remove purple loosestrife.
Click here for more information on Purple Loosestrife.
Japanese Knotweed is an invasive plant found in moist areas that can grow up to 9 feet tall and has the potential to out-compete native vegetation. Currently, it is present in most Maine counties and on Indian Island. There are no known occurences on other tribal lands at this time. People often refer to Japanese Knotweed as "bamboo." Cutting it down is extremely ineffective as often 2 new sprouts will grow from the one stem that was cut down.
Click here for more information on Japanese Knotweed.
PLANTS IN THE WATER
Invasive plants are plants that are not native to an area but when introduced invade and take over. These exotic plants can grow on land as well as in the water, and outcompete the native plants and harm the ecosystem. Once they are introduced to an area they are extremely difficult to control, and the longer they have been in a place it is almost impossible to get rid f them. While this page only cover the invasives that live in water, REMEMBER all invasives are a threat to our beautiful lands, rivers, lakes, and streams.
WHY SHOULD YOU CARE?
Here are some of the reasons why these foreign plants are bad:
- They grow fast
- They take over native plants
- They are hard on fish (at night they use up lots of oxygen)
- They make it harder to swim, fish, and boat.
WHAT CAN YOU DO?
- When you’re out there, take a look around! Notice the common ones (which are most likely native) you see! That way when you do see something very different (the invasive) it will be obvious to you. Try to see as much of the bottom as possible – maybe even use something to help, like a viewing tube. If you do see something very different, try to mark the spot on a map, by an anchored buoy, and take notes of landmarks (shoreline cottages, unusual rocks or trees, etc.) to help others re-locate the site. If you have a GPS, take coordinates. You could also take pictures of the area. Please contact Water Resources Program IMMEDIATELY so that we can investigate further.
- After every trip, be sure to clean all equipment of any plant debris and dispose of it in the trash. These foreigner plants can survive for a very long time on shore with no water, and it is illegal to have them hanging off your boat trailer or other equipment.
- Avoid disturbing plants unless a sample is required. Many water plants (native and invasive) can spread by broken off pieces of any part of the plant. Samples should only be obtained if you have the right equipment and then by a clean cut, if possible. Scoop up any and all pieces with the leaf rake or a net.
WHEN SHOULD YOU DO IT?
July through September is generally the best time of year to start paying attention to the bottom and to look for plants. Before July, many water plants are not fully developed. The flowers that grow above the water are sometimes needed for identification and for many plants flowers do not typically start to develop until July. Curly-leaf pondweed is an exception to this rule, usually reaching maturity by late spring to early summer.
WHY DO WE NEED HELP LOOKING FOR THEM?
WRP does not have enough staff and time to patrol all our waters for these invasives. But with your help, together we can protect our native plants and animals and prevent these plants taking over. We need help from everyone who enjoys our rivers, streams, lakes, and ponds by keeping an eye out for the eleven most wanted invasives, five of which are already in Maine.
Early detection is the best hope of wiping out these pesty little buggers and preventing them from getting established. While getting rid of these plants completely may not be possible, early detection can help manage them effectively using low-impact methods.
WHAT ARE OTHER PEOPLE DOING ABOUT THIS?
The Maine Volunteer Lake Monitoring Program is a widespread citizen group that helps protect Maine lakes through the gathering and sharing of valid scientific information pertaining to lake health. The VLMP trains, certifies and provides technical support to hundreds of volunteers who monitor a wide range of indicators of water quality, assess watershed health and function, and screen lakes for invasive aquatic plants and animals. Since the first Invasive Plant Patrol (IPP) workshop in 2002, the VLMP has trained thousands of individuals to screen Maine waters for invaders. The program was specifically designed to engage widespread participation by individuals with varying amounts of time and expertise to commit to the endeavor, from those who simply want to be more knowledgeable when they are out recreating on their lake, to those who are conducting and leading comprehensive lake-wide searches. The funding the for this program comes from a portion of the state's boat registration fees and donations. The trainings are free, and some of the PIN WRP staff have taken these trainings to increase our knowledge. Here is a link that has all the listing for workshops on plant identification (http://www.mainevlmp.org/invasive-plant-patrol-workshops/).
According to the Maine Volunteer Lake Monitoring Program (MVLMP), "As of March 2013, twenty-four Maine waterways (encompassing forty-six distinct waterbodies) are known to be infested with invasive aquatic plants. Variable water-milfoil is still the most widespread of the known invasive aquatic plants in Maine. Other invasive aquatic plants present in Maine include curly-leaf pondweed, Eurasian water-milfoil, European naiad and hydrilla."
The MVLMP website (http://www.mainevlmp.org/) has a variety of very helpful resources including workshops to train you how to identify invasive plants, and how to conduct courtesy boat inspections, a map of all the lakes they have been to, and other tools to use to help protect lakes.
If you have any questions or comments feel free to contact DNR anytime! Woliwoni
(click on section titles in brown to expand or contract them)
1.) Variable water-milfoil (Myriophyllum heterophyllum)
Description: Variable water-milfoil is an underwater, plant with branching stems rising out from above the surface with compact, spreading roots.
Habitat: Variable water-milfoil is an extremely well adapted plant, able to thrive in a wide variety of environmental conditions. It grows well in still and flowing waters, and can survive under ice. Variable water-milfoil grows rooted in water depths from 1 to 5 meters on various bottom types including biological muck, silt, sand and gravel.
Annual Cycle: Variable water-milfoil is an extremely rugged watery perennial that grows through root division, broken pieces, young shoots, and seeds. Flowering spikes typically rise from the water in mid to late summer, but not all colonies produce flowers. Self-shattering may occur during the growing season with stem sections developing roots even before they separate from the parent plant. Toward the end of the growing season some plants break apart and die back to their rootstalks; others overwinter intact. New growth sprouts from young shoots, roots, overwintering plants and plant debris as the water begins to warm in the spring, growing rapidly toward the surface. Certain milfoils are able to interbreed with other, closely related, milfoil species.
Origin and U.S. Range: Variable water-milfoil is native to parts of the United States, but not native to New England. Variable water-milfoil is present in the Songo River at Sebago Lake State Park in Maine and all New England states except Vermont. A hybrid of this species (M. heterophyllum x M. laxum), has also been confirmed in Maine.
2.) Curly-leaf pondweed (Potamogeton crispus)
Description: Curly-leaf pondweed has underwater leaves only. Mature stems may be several meters in length. The leaves of this plant are key to its identification. When visible, (they disintegrate early in the plant’s growth cycle) are slightly joined to the stem at the leaf base and 4 to 10 mm long. Flower spikes appear above the surface of the water from June through September.
Habitat: Curly-leaf pondweed is found in the underwater plant community. Generally preferring soft sediments, it grows in waters that are shallow or deep, still or flowing. Curly-leaf thrives where many other aquatic plants do not, for example in waters that are shaded, disturbed, polluted or turbid.
Annual Cycle: Curly-leaf pondweed, an aquatic perennial, is adapted to growing in cool conditions. Plants sprout in the late fall and grow through the winter, reaching maturity relatively early in the season (late spring through early summer). Flowers are produced during the growing season and the plants generally begin breaking up by mid-July. Curly-leaf pondweed produces seeds. Little is known, however, regarding the importance of seeds in the spread and reproduction of this plant.
Origin and U.S. Range: Curly-leaf pondweed is native to Eurasia. Introduced to the United States some time during the mid1800s, it has since spread to almost every state in the country. In addition to spread by natural causes and recreational activity, curly leaf pondweed has been planted intentionally for waterfowl and wildlife habitat, and possibly has been spread as a contaminant in water used to transport fish and fish eggs to hatcheries. Curly-leaf has infested West Pond in Parsonsfield in southern Maine and is currently present in the nearby states of New Hampshire, Massachusetts, Vermont, Connecticut, New York and Rhode Island.
3.) Eurasian water-milfoil (Myriophyllum spicatum)
Description: Branching stems of Eurasian water-milfoil emerge from thick, spreading roots. Eurasian water-milfoil does not form winter buds.
Habitat: Eurasian water-milfoil is an extremely well adapted plant, able to thrive in a wide variety of environmental conditions. It grows well in still and flowing waters, endures mild salinities and can survive under ice. Eurasian water-milfoil grows rooted in water depths from 1 to 10 meters, generally reaching the surface in depths of 3 to 5 meters. Though adapted to a wide variety of substrate types, this species seems to favor fine-textured, inorganic (lifeless) sediments.
Annual Cycle: Eurasian water-milfoil is an extremely hardy aquatic perennial that grows through root division, broken pieces, and seeds. Flowering spikes typically rises from the water in mid to late summer, but not all colonies produce flowers. Splintering may occur during the growing season with stem sections developing roots even before they separate from the parent plant. Toward the end of the growing season some plants break apart and die back to their rootstalks; others overwinter intact. New growth sprouts from roots and overwintering plants and plant pieces as the water begins to warm in the spring, growing rapidly toward the surface. Certain milfoils are able to sneak in with other, closely related, milfoil species. Eurasian water-milfoil is known to sneak in with Maine’s native northern water-milfoil.
Origin and U.S. Range: Eurasian water-milfoil is native to Europe and Asia. It was introduced to North America in the 1940s. Spreading rapidly since its introduction, Eurasian water-milfoil is now present in most states, including in the Scarborough quarry pond of Maine. It also occurs in most Canadian provinces including Quebec.
4.) European naiad/ Spiny Naiad (Najas minor)
Description: Unlike most water plants, European naiad is a true annual. Seedlings grow from slender roots, developing stems up to 2.5 meters long that often branch abundantly near the top.
Habitat: European naiad is found in the underwater plant community, growing in ponds, lakes, and slow moving streams in depths up to 5 meters. Preferring sand and gravel, the plants thrive in a wide range of bottom surfaces.
Annual Cycle: A true annual, European naiad grows anew from seeds each spring. Seeds form in the leaf stem from July through September. Although European naiad can reproduce by broken pieces during the growing season, the primary means of reproduction appears to be by seed. It is estimated that a productive, one-acre infestation will produce tens of millions of seeds per season. During the late summer or early fall, the stems of European naiad become brittle, and break up. Seeds remain attached in the leaf axils, and wind and water currents disperse the pieces.
Origin and U.S. Range: European naiad is native to Europe. It is thought to have been introduced to the US sometime in the early 1900s and is now present in much of the Eastern United States including the nearby states of New Hampshire, Massachusetts, Vermont, and New York. European naiad is currently in Legion Pond in Kittery Maine. (In 2010 curly leaf pondweed was also found in Legion Pond, making this Maine’s first known “double infestation.”)
5.) Hydrilla (Hydrilla verticillata)
Description: Hydrilla is a perennial underwater aquatic plant with long slender, branching stems rising from horizontal underground. Identification of hydrilla is complicated by the fact that there are two distinct forms occurring in the United States.
Habitat: Hydrilla is found in the underwater plant community. The adaptability of this plant to a wide variety of environmental conditions has earned hydrilla its reputation as the perfect weed. Hydrilla can grow in a variety of bottom surfaces, in waters still or flowing, low or high in nutrients. Hydrilla may also threaten estuary systems, tolerating salinities up to 10 parts per thousand. Remarkably adapted to low light conditions, hydrilla can photosynthesize earlier and later in the day than most plants, grows well in murky water and, when the water is clear, to depths exceeding 10 meters. Hydrilla typically occurs in thick, rooted stands, but live pieces may also be found drifting in large mats. Hydrilla is considered one of the most problematic of all water invaders.
Annual Cycle: Hydrilla sprouts in the spring, the leafy stems grow rapidly (about 2 cm per day) toward the surface. Flowers, buds and bulb-like structures are produced during the growing season. The buds drop to the sediments when the leafy vegetation begins to break up in the fall. The plants die back completely to the sediments by early winter, a remarkable vanishing act given the amount of biomass involved. The buds will sprout the following spring, but the bulb-like structures may remain dormant for several years in the sediments. Research indicates that one bulb-like structures can lead to the production of over 5,000 new bulb-like structures per square meter. The bulb-like structures and buds can withstand ice cover, drying, ingestion by waterfowl, and herbicides. Studies also indicate that the form found in Maine, puts more of its energy into bulb-like structures and bud production than the other form, and may have a greater potential for spread by these means. In addition to reproducing like plants by way of bulb-like structures and buds, hydrilla grows readily from stem or broken root pieces. New plants can sprout from stem pieces.
Origin and U.S. Range: Hydrilla is native to Africa, Australia, and parts of Asia. The dioeciously form, found primarily in more southern latitudes, was first introduced to the US through the aquarium trade during the mid-1900s. The monoecious form, found primarily in northern latitudes, was introduced some time later and has now been confirmed in several New England states, including Pickerel Pond in Maine, Connecticut, Massachusetts and also New Jersey.
6.) European Frog-Bit (Hydrocharis morsus-ranae)
Description: European frog-bit is a small free-floating water plant. Its small kidney or heart shaped leaves (1.5 to 6.5 cm long) are not anchored to the bottom sediments.
Habitat: European frog-bit (or frog’s bit) is found in the floating-leaved plant community. It is a free-floating plant that thrives in open marsh habitat and quiet backwaters, forming thick floating colonies.
Annual Cycle: European frog-bit is an water perennial that grows primarily by vegetative means. Mature plants send out multiple offspring on trailing runners. Winter buds form during the summer, and fall to the bottom as plants begin to decay at the end of the growing season. In the spring the buds break dormancy, bob to the water surface, and sprout new growth. Flowers, followed by fruits, occur during the summer.
Origin and U.S. Range: European frog-bit is native to Europe. It is not native to New England and is considered invasive to this area. Nearby populations occur in Vermont and New York.
7.) Water Chestnut (Trapa natans)
Description: Water chestnut has two distinct leaf types. The floating leaves are somewhat triangular (or fan shaped) in form, with clearly serrated along the outside edges. The upper surface of the leaf is glossy, the undersides covered with soft hairs.
Habitat: Water chestnut grows in the floating-leaf and underwater plant community. It thrives in the soft sediments of quiet, nutrient rich waters in lakes, ponds and streams. The plant is well adapted to life at the water’s edge, and prospers even when stranded along muddy shores.
Annual Cycle: Unlike most water plants, water chestnut is a true annual. Plants sprout anew each year from seeds overwintering in the sediments. Underwater stems grow rapidly to the surface, where the floating rosettes form and the flowers and fruits develop. During the growing season rosettes may become detached and float to new areas. Water chestnut flowers from July to September. The fruit, or nuts, begin to appear by late summer. Each water chestnut seed can produce 15 to 20 new rosettes and each rosette can generate up to 20 seeds. At the end of the growing season, frost kills the plants and decomposition is rapid. The nuts fall and sink into the sediment where they overwinter and sprout in the spring. The nuts may remain viable for up to 12 years but most germinate within 2 years. The nuts have sharp barbs that readily attach to boating gear and wildlife and are easily dispersed by natural and human processes.
Origin and U.S. Range: Water chestnut is native to Europe, Asia and tropical Africa. It is cultivated in Asia and other parts of the world where the fruit is eaten. It was brought to this country in the late 1800s as a showy botanical garden specimen and later escaped to become a noxious aquatic invader. Nearby populations occur in New Hampshire, Connecticut, Massachusetts, New York, Vermont and Rhode Island.
Look a likes: Water chestnut is not easily confused with other aquatic plants.
8.) Yellow Floating Heart (Nymphoides peltata)
Description: Rounded to heart-shaped floating leaves rise on long stalks from rooted stems. Each rooted stem supports a loosely branched group of several leaves. Note that all heart-shaped floating leaved plants that are native to Maine produce only one leaf per rooted stem. The leaves are typically wavy (shallowly scalloped) along the outer edges and have purplish undersides.
Habitat: Yellow floating heart is found within the floating-leaved plant community. It can grow in various substrates (sand, mud, gravel, etc.), in littoral areas ranging from the damp mud along the water’s edge to water depths of 4 meters.
Annual Cycle: Yellow floating heart is an aquatic perennial that grows by seeds, broken pieces, and spreading creeping underground stems. Most floating leaved plants lack the ability to grow by broken pieces, but in the case of yellow floating heartbroken leaves with attached stem parts will form new plants. Viable seeds are produced abundantly and sprout readily. Seed hairs help the seeds float and aid their attachment to waterfowl, increasing possibility of spread to new areas.
Origin and U.S. Range: Yellow floating heart is native to parts of Europe and Asia. It is not native to North America and was introduced to this country as an ornamental pond species. Nearby populations occur in Massachusetts, Vermont, Connecticut and New York.
9.) Parrot Feather (Myriophyllum aquaticum)
Description: Long unbranched stems arise from roots and creeping underground stems. Unburied creeping underground stems function as a support structure for unusual roots, and provide resilience for developing growth. Developing stems may grow to a height of 30 cm above the water surface. Slender, feather-divided leaves occur along the trailing stems in groups of 4 to 6 leaves. Groups are openly spaced toward the base, and more closely arranged toward the growing tip. The developing leaves are hearty, vibrant green, and covered with a waxy coating. Underwater leaves, in contrast, are limp and brownish, and often in a state of deterioration. Small white flowers (female only) are hidden.
Habitat: Parrot feather is found in both the developing and the underwater plant communities of freshwater lakes, ponds, and slow moving streams. It is also adapted to waters with some salinity. While it grows best when rooted in shallow water, it has been known to occur as a floating plant in the deep water of nutrient-enriched lakes. It is well adapted to life at the water’s edge and can survive when stranded on dewatered river banks and lake shores.
Annual Cycle: Parrot feather is an water perennial that grows through root division and broken plant pieces. Plants usually flower in the spring but fall flowering also occurs. Male and female flower parts occur on separate plants, and male plants are only known to occur in the plant’s native range. As a result, parrot feather populations in the United States do not produce seeds. Plants die back to their creeping underground stems toward the end of the growing season. New shoots begin to grow rapidly from overwintering creeping underground stems as water temperatures rise in the spring.
Origin and U.S. Range: Parrot feather is native to South America, and is considered invasive in the United States. Nearby populations occur in New York and Rhode Island. Parrot feather is not known to be present in Maine waters.
10.) Fanwort (Cabomba caroliniana)
Description: Stems rise at intervals from slender roots. Fanwort has two distinct leaf types. Underwater leaves are finely divided, widely branched, and held apart from the stem on slender leaf stems, and looks like tiny fans with handles. The leaves are strictly arranged in opposite pairs along the main stem. The orderly formation of leaves and stems gives the plant a tubular appearance underwater. Plants range in color from grass green to olive green to reddish. Small white flowers (1 cm in diameter) develop among the floating leaves. Habitat: Fanwort is found in the underwater and floating-leaved plant communities, growing in a variety of substrates including sand, mud and gravel. It thrives in stagnant or slow moving waters of lakes, pond and streams in depths of up to 2.5 meters. Large mats of drifting pieces may occur.
Annual Cycle: Fanwort is an water perennial that grows primarily from stem pieces and root expansion. In the spring, new growth rises from buried roots and overwintering stem pieces. Plants grow rapidly to the surface, often forming thick mats. Flowers are produced from May to September. Although fanwort is self-breeding, seed germination in areas beyond its natural range does not appear to be significant. Both the roots and stems are easily broken as the season progresses, helping vegetative spread to new areas.
Origin and U.S. Range: Fanwort is native to South America. The previously held belief that this plant is also native to some parts of the southeastern United States is now under debate. It is not native to New England. An attractive plant, fanwort has long been popular in the aquarium trade. Release from aquaria into the environment is considered to be one of the ways this plant has spread beyond its natural range. Fanwort occurs, and is considered invasive, in many parts of the United States including the nearby states of New Hampshire, Massachusetts, New York, and Rhode Island.
11.) Brazilian Waterweed (Egeria densa)
Description: Underwater stems rise from trailing, unbranched roots. Bright to dark green leaves are thickly arranged in groups of 4 to 6 leaves along slender stems. (Note: some lower leaves may occasionally occur in opposite pairs or in groups of 3 leaves.) The small flowers (2 cm in diameter) have three white petals and a yellow center, and rise just above or at the surface on slender stalks. Unlike its invasive look alike hydrilla, Brazilian waterweed does not produce bulb-like structures.
Habitat: Brazilian waterweed is found in the underwater plant community. It may grow in bottoms with sand, mud or stone to depths of 6.5 meters. A resilient plant, most of its biomass is produced near the water surface. Infestations of Brazilian waterweed may occur in large thickly rooted stands, and drifting mats.
Annual Cycle: Brazilian waterweed is a rooted, underwater perennial. Areas on the stems play an important role in food storage and reproduction. Unusual roots and branches are both produced from the stem. If a piece of Brazilian waterweed does not have a double node, it cannot grow into a new plant. Regrowth of piece of the plant containing a double node is the only means for reproduction. Only male flowers are present on plants found in the US, therefore no seeds are produced. Brazilian waterweed prefers moderate water temperatures, and optimum growth occurs in the spring and fall. During the summer growth may slow, or cease completely. Plants will die back to their roots in the winter.
Origin and U.S. Range: Brazilian waterweed is native to South America. It has been widely distributed in the United States (usually under the name “anacharis”) as an aquarium plant and a beneficial oxygenator for water nurseries. Brazilian waterweed is currently present in many parts of the US including the nearby states of New Hampshire, Massachusetts, Vermont and New York.
12.) Chinese Mystery Snails (Cipangopaludina chinensis malleatus)
Description: Chinese mystery snails are distinctively large; at the size of a walnut or golf ball, they are half-again as large as Maine’s largest native freshwater snail. Though they spend a good portion of their lives under the water surface, half buried in the bottom sediments, Chinese mystery snails may also be encountered with their trap doors sealed up tight, floating along at the water’s surface. When these large snails die, they often wash up on shore, where their dark, olive-colored shells can be easily seen and (unpleasantly) smelled.
Habitat: Chinese mystery snails prefer the quiet water of lakes, ponds, roadside ditches and slower portions of streams.
Origin and U.S. Range: Chinese mystery snails, native to parts of Southeast Asia, were brought to this country as a food source for Asian markets. It is believed that imported snails were intentionally released in some areas to create a locally-harvestable supply. Since their introduction, Chinese mystery snails have spread too many parts of the United States, and can now be found in a number of Maine lakes and ponds.