Family: Cabombaceae
  Gray.  (Carolina fanwort)

Field Description: Submersed aquatic perennial with low-branching stems forming two types of leaves. Submersed leaves are opposite, fan shaped and dissected into linear segments, each segment ending in a blunt tip. Floating leaves are alternate, smaller and diamond in shape. Flowers are borne singly, colored white to purple, and form elongated fruits with 3 seeds.
Habitat: Prefers ponds and lakes yet will colonize slow-moving streams in water 1 - 3 m deep.
Native Range: Southeastern United States, north to and including Virginia. Also native to South America.
Nonindigenous Range: Established sporadically in the Northeast, Great Lakes and northwest regions of the United States. Introduced in the Mid-Atlantic States north of Virginia where populations have been documented since the late 1800s.  Widely distributed and common throughout the coastal states, less occasional inland.

DE PA NJ NY CT RI MA VT 1897 1938 1901 1996* 1937 1932 1895 1962

Comments: Persistent and competitive with the ability to form dense stands.  Invasive where introduced in the U.S., as well as in Australia, India and Japan. Reproduction by seed is rare in the northeastern U.S., plants spread and perennate by vegetative fragments. Submersed plants are often mistaken for Myriophyllum or Limnophila.  Historical plant of the aquarium trade still sold today.

Family: Haloragaceae
  (Vell.) Verdc. (parrot feather)

Field Description: Submersed stems are lanky with widely spaced feather-like leaves.  Recognize this species by the distinctive emergent leaves that form dense blue-green masses of foliage that extend to 20 cm above the water. Entire plants become amphibious with water drawdown. Inconspicuous female flowers located in the leaf axils are rarely seen.  
Habitat: Shallow, sluggish waters to 1 m deep, including swamps, ponds and ditches.
Native Range: South America.
Nonindigenous Range: Occurring most frequently, often to become locally dominant, in the southern United States and Hawaii.  Occasionally established in more temperate states.  Introduced to the Mid-Atlantic States, especially in Virginia where it heavily colonizes sites in over ten counties. Sporadic and less occasional in the remaining states although extending recently as far north as Connecticut (Quinnipiac drainage).

VA  WV  MD  DE  PA  NJ  NY  CT 1970 1970 1950 1980 1950 1890 1929 2001

Comments: The absence of male plants in the U.S. implicates reproduction solely by vegetative propagules.  Mat formation is prevalent in the southern U.S.  Potentially invasive through the lower half of Region 5.  Popularly sold as a water garden ornamental as well as an aquarium plant, this species readily escapes cultivation. 

  Michx. (two-leaf water milfoil)

Field Description: Submersed aquatic perennial with thick red-green stems (3-6 mm). Brittle, filamentous leaves are arranged in compacted whorls spaced closely apart (3-6 mm) on the stem.  Each leaf dissected into 16-24 filaments with the lower filaments as long as or longer than the leaf axis.  Tips of flowering stems emerge 15-30 cm to carry tiny sessile, reddish flowers above leafy bracts.
Habitat: Lakes, streams and marshes to 3 m deep.
Native Range: Central and eastern United States, excepting portions of the Northeast,notably New England.  Considered rare and endangered in Pennsylvania, probably native in western New York.
Nonindigenous Range: Introduced and widely spreading in New England since the early 1930s. Locally abundant in Connecticut, Rhode Island and Massachusetts. Increasing in range in eastern New York since the 1950s where plants are reportedly introduced. Recently spreading to new drainages in New Hampshire and Maine. Native range in other Mid-Atlantic States is not adequately understood.  A recent New Jersey occurrence demonstrates dense monospecific growth in deep water that dominates the water column and surface waters, a characteristic of many of the invasive New England populations.

NJ NY CT  RI MA  NH  ME 2003 1953 1932 1983* 1940 1983* 1983*

Comments: Molecular analysis reveals that New England populations are comprised of two distinct introduced entities Myriophyllum heterophyllum and a newly described hybrid M. heterophyllum X M. pinnatum (Moody and Les, 2003).  The hybrid developed outside of the region. Both entities were likely introduced through the aquarium trade.  Myriophyllum heterophyllum rarely exhibits invasive characteristics, generally growing in scattered stands interspersed with native plants.  However, the introduced hybrid forms large, aggressive, dominating populations of management concern.  Plants propagate primarily by vegetative stem fragments.  Winter buds are produced along the stems and the rhizomes.  Waterfowl eat the fruit and may aid in dispersal.

  L. (Eurasian water milfoil)

Field Description: A submersed, rooted, perennial herb consisting of long underwater branched stems that can reach 1.8 - 2.7 m in length and produce many whorled, finely divided feathery leaves upon nearing the surface. Leaves are divided into threadlike leaflets that are ranked in compact pairs of more than 14.  Overall, the leaf shape resembles an equilateral triangle, curved at the base. Whorled flowers on emergent spikes produce a globular, 4-lobed fruit late in the season.
Habitat: Lakes, ponds, shallow reservoirs and low energy areas of rivers and streams, with the capability of inhabiting brackish waters.
Native Range: Europe, Asia, and northern Africa.
Nonindigenous Range: Established in nearly all parts of the United States, excepting Maine, Montana, Wyoming, Alaska, Hawaii and Rhode Island.  Very frequent in the Mid-Atlantic States where the first national introductions occurred and 90 river drainages have since become infested. Common and widely distributed in freshwater lakes and rivers, where in many states native submersed species, such as Myriophyllum sibiricum, are in decline.  Fluctuating with salinity in tidal regions of the Chesapeake Bay. More tolerant of salt intrusion and industrial pollution than native submersed plants in the Delaware River.

VA  WV  MD  DE  PA  NJ  NY  CT MA  VT  NH 1992 1982* 1942 1997 1950 1952 1968 1983* 1971 1962 1992

Comments: Aggressive colonizer forming dense underwater stands. Particularly troublesome in waterbodies that have experienced disturbances such as nutrient loading, intense plant management, abundant motorboat use, and fluctuating water levels.  Reproduces by plant fragmentation and seed. Distinguish this species from the native Myriophyllum sibiricum primarily by the shape of the leaf and secondly by the number of leaflets.  Myriophyllum sibiricum has basal leaflets that are as long as the leaf, curving over and extending almost to the top of the leaf. Myriophyllum spicatum leaflets are usually in pairs of more than 14 (Nichols, 1975) and are uniformly tapered so that the leaf shape is more like an equilateral triangle with a curved base.

Family: Hydrocharitaceae
  Planch.  (Brazilian waterweed)

Field Description: Continuously submersed aquatic perennial producing single (or few branching) stems, commonly 0.3 - 0.6 m long, capable of reaching 6 m. Leaves entire, sessile and in whorls, measuring to 2-3 cm or longer with lance shaped tips and minute marginal serrations.  When run through the hand, plant strands are overall smooth in texture. White flowers rise above the water, but no seeds are produced, as only male plants occur in the U.S. 
Habitat: Still and flowing waters of ponds, lakes, streams and ditches.
Native Range: South America.
Nonindigenous Range: Scattered yet established from coast to coast in the continental United States, including Hawaii.  Persisting at a few locales in most Mid-Atlantic States.  Although several early populations were short term, the species is well established and expanding to new territories.  In 2001, its first record for New Hampshire occurred in the Merrimack drainage.

VA  MD  DE  PA  NJ  NY  CT  MA  VT  NH 1946 1938 1941 1917 1990* 1893 1985 1939 1913 2001

Comments: Commonly forms dense populations.  Potentially invasive in Region 5 where new populations could arise from the spread of vegetative propagules by birds and boats. Hydrilla and Egeria are often found growing together, yet each species may fluctuate seasonally in abundance.  Resembling and often confused with Hydrilla or native Elodea species. Introduced as an escapee from aquaria and still widely sold, although often under the incorrect names of Elodea densa or Anacharis densa.

  L.f. Royle (hydrilla)

Field Description: Continuously submersed aquatic perennial with long ascending stems. Monoecious plants usually branching lower to blanket the bottom substrate, dioecious plants branching at the surface then growing horizontally to form floating mats. Leaves entire, sessile and in whorls, measuring to 1.5 cm with the opposite sides mostly parallel until reaching the tips. Teeth along leaf margins and under the midrib impart a rough texture when strands are drawn through the hand.  Translucent, white flowers with 3-6 petals rise above the water surface.  Monoecious plants produce male and female flowers and rarely develop fruit - a soft, spiny, few-seeded capsule. Dioecious plants produce only female flowers and are sterile.
Habitat: Freshwater lakes, ponds, rivers, impoundments and canals.
Native Range: The dioecious type likely originated from the Indian subcontinent, the monoecious type from temperate Korea (Madeira et al., 1997).
Nonindigenous Range: Frequently established in the perimeter states of the continental United States. Southern populations are predominantly dioecious and plants north of South Carolina are monoecious.  Established in 18 drainages and spreading in the Mid-Atlantic States, a region that appears vulnerable throughout. Dominating submersed plant beds in rivers and tidal freshwater marsh creeks in Maryland and Virginia, appearing in downtown Philadelphia in the Schuylkill River and reoccurring in ponds and reservoirs in remaining populated states. Recorded in the Pinelands National Reserve, New Jersey. New to Maine in 2002 at a pond in the Saco drainage where viable tubers overwintered in the substrate while the pond remained iced over from November to April. In 2003, the first documented occurrence for the state of New Jersey was reported from a small lake in the Lower Delaware drainage.

VA MD  DE  PA  NJ  CT MA ME 1982 1982 1976 1996 2003 1987 2001 2002

Comments: Highly invasive and competitive, often to become the dominant species where introduced.  Has the ability to alter physical and chemical characteristics of lakes; affects water flow and water use. Often confused with Egeria densa and Elodea spp. but readily distinguishable by its production of turions and tubers, both important features for overwintering and reproduction. Tubers are resistant to most control techniques and may be viable as a source of reinfestation for years.  Propagates through the growing season by stem fragmentation. 

Family: Najadaceae
  All. (brittle naiad)

Field Description: Submersed stems on this annual aquatic are notably slender, to only 1 mm thick, and highly branched.  Leaves are narrow, nearly linear, with serrated margins and arranged oppositely but may appear whorled. 1-seeded fruits are common and easily found late spring to fall deep in the leaf axils and surrounded by the leaf sheath.
Habitat: Prefers slow moving waters of streams, ponds, lakes and canals in water up to 4.6 m deep.
Native Range: Europe, Turkey, northern Africa, India and Japan.
Nonindigenous Range: Established occasionally through the eastern half of the United States.  Scattered populations exist in the Mid-Atlantic States, with the first sighting originating from the Hudson River drainage. New populations are distributed across Region 5 suggesting the potential for establishment throughout this range.

VA  WV MD  PA  NY MA  VT  NH 1985 1996* 1982 1951 1934 1974 1965 1992

Comments: Often found in eutrophic and alkaline waters and in association with Hydrilla verticillata and Egeria densa.  An extremely fragile plant, its fragmentation aids in its dispersal and potential for spread. Najas depends on seed germination for annual regrowth. Seed may also be dispersed by waterfowl.

Family: Potamogetonaceae
  L. (curly pondweed)

Field Description: Conspicuous teeth and strong undulations at the leaf margins distinguish this pondweed, which, excepting the inflorescence, has all parts submersed.  Flowers are loosely arranged on emersed spikes.  Reproduces by fruits and turions (budlike propagules at tips of branches) produced in early summer after which plants decline.  
 Habitat: Ponds, lakes and streams; tolerates brackish waters, as well as nutrient-rich or alkaline freshwaters.
Native Range: Europe, Middle East, northern Africa, India and Australia.
Nonindigenous Range: Established and frequent throughout the United States except Alaska and Maine.  Known in the Mid-Atlantic States for over 100 years. Found through more than 80 drainages in Region 5.  Especially abundant in tidal rivers and bays, such as the Chesapeake Bay and tidal Potomac.

VA WV  MD  DE  PA  NJ  NY  CT  RI MA  VT  NH 1874 1930 1877 1860 1861 1866 1879 1932 1932 1880 1911 1984

Comments: This is an aggressive, cool climate species that is potentially invasive to the entire Mid-Atlantic region.  Turions produce new plants in late summer or fall.  These new, small plants overwinter and give this species a competitive advantage by developing before other species in the spring.  Seed viability in the U.S. remains unclear. Creates eutrophic waters from the high amount of decaying plant matter when plants die off after flowering.  Sold as an aquarium plant.