Aquatic Plant Species

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Alligatorweed (Alternathera philoxeroides)
Life History:
Native to South America.
Summer perennial that grows to around 1-2 m and whose horizontal stolons can reach 10 m. Was substantially more abundant in the SE U.S. 40 yrs ago than now.

Distribution:
Native range of is reportedly the Parana River region of South America. Can now be found elsewhere in South America, and on the continents of North America, Australia, and Asia, and on a number of adjacent islands.
In the United States, A. philoxeroides occurs throughout the SE from VA south to FL and west to TX. Has been reported as far north as IL, and now also occurs in CA.

Anatomy & Physiology:
Leaves and stems vary greatly in size and shape. Fleshy, succulent stems can grow horizontally and float on surface of the water, forming rafts, or matted clumps which grow onto banks. The horizontal stems (called stolons) may reach a length of 10 m. The leaves are opposite in pairs, with a distinctive midrib, and range in size from 5-10 cm.
Fibrous roots arising at stem nodes may hang free in water or penetrate into the sediment. Flowers, which appear from December to April, are thin and clover-like in shape. White flowers grow on stalks and are approximately 1.25-7.6 cm in length and 13 mm in diameter. Often forms very dense stands or mats that make shoreline access difficult. Aquatic stems are hollow and can be single or branched. Leaves are opposite, long, elliptical or lance-shaped up to 3/4 inch wide and 5 inches long with a prominent midrib. Often roots develop at leaf nodes. Soft, whitish hairs are found in the leaf axis. Single flowers are small (about 1/2 inch in diameter) white, fragrant clusters of 6 to 10 florets, borne on long branches (to 3 inches). The flowers resemble those of white clover. A single seed develops within the fruit.

Reproduction:
Reproduction is predominantly through vegetative means; individuals rarely produce seeds, and when they do the seeds are typically non-viable. Vegetative growth occurs at the apical stem buds and axillary stem and root buds and the plant is spread through fragmentation.

Habitat Characteristics:
Alligatorweed occurs in a range of habitats ranging from dry terrestrial to aquatic. To facilitate buoyancy, plants growing in aquatic habitats tend to have stems that are hollow and larger than those of plants growing on land.

Behavior:
Submerged portions of all aquatic plants provide habitats for many invertebrates. These in turn are used as food by fish and other wildlife species. After aquatic plants die, their decomposition by bacteria and fungi provides food for many aquatic invertebrates. Alligator weed has no known direct food value to wildlife and since it is a non-native should not be spread.

Control Methods:
None; Mechanical removal of mats is costly, and often results in dispersal of large #s of vegetative fragments that can exacerbate the infestation. Although biocontrol by means of the aligatorweed via flea beetle (Agasicles hygrophila) and other control agents has greatly lowered the threat of this plant, the cost associated with carefully studying, planning and managing the release of biocontrol agents is substantial.

Laws & Regulations:
Illegal to possess or transport
Brazilian Waterweed (Egeria densa)
Distribution:
This invader is originally from South America and, with the unintended help of aquarium enthusiasts, has invaded most continents. In the United States, the plant is present in the Pacific Northwest, CA, UT, IL, NE, KS, TX, the Southeast, and in the East from New England to FL. As of 2002 it has not been documented in MN. Was considered a desirable aquarium plant because it is a good "oxygenator." It was probably transmitted into natural areas by people pouring the contents of their aquariums into nearby lakes and streams.

Anatomy & Physiology:
Submerged aquatic perennial plant with a trailing growth habit. The basic structure of the plant is a stem with whorls of four to six small leaves. Leaves vary from one-half to one-and-a half inches in length and are sessile (lacking a stem). Brazilian waterweed leaves are noticeably longer and wider than our native waterweeds. Unlike our native waterweeds, which have a smooth leaf margin, Brazilian waterweed has tiny fine teeth along its leaf margins. Plants produce three-quarter-inch wide white flowers that are elevated about an inch above the water. All North American populations of Brazilian waterweed reproduce vegetatively as no seeds and/or female flowers have ever been observed on populations found here. Vegetative reproduction is achieved by lateral buds arising from numerous specialized nodal regions on the stems. Only fragments containing specialized nodes can develop into new plants. Brazilian waterweed fragments easily, which promotes the sprouting of new plants.

Habitat Characteristics:
Brazilian waterweed grows in water up to 20 feet deep and often occurs in warm freshwater ponds, lakes and reservoirs as well as in slow-flowing streams and sloughs.

Control Methods:
The best way to control this species or any aquatic invader is to prevent it from being introduced in the first place. Anyone engaged in activities in Maine's waters should be aware of the potential for spread of invasive plants and take steps to prevent their introduction. Your actions can make a difference. Simple things you can do include inspecting boats, motors and trailers at the boat ramp before launching them, and again after you haul them out. Prevent plant material from getting into bait buckets and live wells, and from getting tangled up in anchor ropes or fishing gear. Plants cleaned from boats and gear should be disposed of in a trash receptacle or away from water on dry land.
Once established, invasive aquatic plants are extremely difficult to eradicate. Control has been attempted with water level manipulations, mechanical control and herbicides. In most cases these plants have survived attempts at control. Biological controls for invasive aquatics are still being researched and may help limit growth of some species in the future. Note that the use of herbicide in Maine waters is strictly regulated. Only licensed professionals with a permit from the Department of Environmental Protection may carry out herbicide treatments in Maine's waters. Hand pulling of invasive aquatic plants also requires a permit. Also note that in Maine it is illegal to possess, import, cultivate, distribute or transport Egeria densa.

Laws & Regulations:
Curly Pondweed (Potamogeton crispus)
Life History:
A popular aquarium plant, curlyleaf pondweed was accidentally introduced to U.S. waters by hobbyists in the mid 1800's. The species first became established in the northeastern United States. By the 1930s it was established in the Midwest and is now readily present in nearly all of the lower 48 states.

Distribution:
Native to Eurasia, Africa, and Australia. Now reported in all of the continental US except for MN and SC.

Anatomy & Physiology:
Oblong blue-green leaves that attach to its spaghetti-like stems in an alternate pattern. Margins of the leaves are wavy and fine-
toothed. Leaves can be up to 3 in long and a 1/2 in wide. Produces small flowers that are arranged on dense terminal spikes that rise a few inches above the surface of water. In the spring, plant produces dormant vegetative propagules known as turions. Turions look like small greenish brown pinecones.

Reproduction:
Production of dormant vegetative propagules called turions. 100s of turions can be produced by each plant, and they can be dispersed by water currents. Turions are produced in the late spring, just before the plants begin to die. Turions remain dormant in the sediment through the summer until cooling water temperature triggers their germination in the fall. The germination rate of turions is very high, some estimates indicate between 60- 80%. Turions can also remain viable in the sediment for a # of yrs. Plants will also grow from the rhizomes of past plants.

Habitat Characteristics:
Considered a deep-water plant, but it will colonize in shallow water as well.

Behavior:
With a strong rhizome anchoring syst, can grow in a variety of diff locales and sediment types. Can tolerate extreme conditions including low light and cold water temperatures and has even been found growing under 20 in of snow covered ice. Actively grows during the winter months when most plants are dormant. Reaches its max. density in late spring and dies back in midsummer when most plants are at their peak of seasonal growth. Transportation is through the transport of plant fragments on aquatic equipment such as boats and trailers. These fragments can root and create a new infestation. Once the plant is established in a body of water it can spread quickly. Each plant can yield hundreds of turions. Water currents and wave action can transport turions throughout a waterway

Control Methods:
Prevention. Key is to remove the plant before turion production. Control efforts should take place for a # of consecutive yrs since some turions lay dormant for a few growing seasons. Early season mechanical removal using weed harvesters, hand cutting, or raking are possible methods of control. Plants should be removed as close to the sediment surface as possible to reduce turion product. All fragments must be removed from the body of water for this to be effective. To dispose of the remnants, composting, burning, burying, or trash disposal are all acceptable methods. Early spring treatments using contact herbicides with active ingredients of diquat or endothall. Chemical app of diquat or endothall should occur when the water temp is around 50 to 55 degrees to greatly reduce turion product. Fluridone applied early in spring has inhibited turions. Fluridone should only be used for large scale or whole lake treatments, whereas diquat or endothall may be used over isolated beds of curlyleaf or large scale treatments.
Eurasian Watermilfoil (Myriophyllum spicatum)
Life History:
1st introduced to USthru aquarium trade. 1st documented ID of it in open water in the US was in 1942. By 1950 species was into Midwest in OH and was also found in western states (AZ & CA). Now found throughout continental US w/ exception of northern Great Plains region and MN.

Distribution:
Native to Europe, Asia, and northern Africa. As of 2003, 45 states reported the presence of it. Has spread thru accidental and intentional introductions. Pond owners intentionally put it into ponds to give fish habitat. Since it is capable of reproducing by vegetative means, the spread into new bodies of water has been by fragments. Aquatic equip. used @ infested waters may have frags attached; can be transported to other waters & start new infestation. Plant can stay alive for weeks out of water if kept moist.

Anatomy & Physiology:
Submersed perennial. Long underwater stem that branches profusely when it reaches surface of water. Leaves are whorled on stem at each node, and there are generally 4 leaves per whorl. Leaves are finely divided and feather-like. There are 12 to 21 pairs of leaflets. Each leaflet is thin, fine and about ½ inch long. It produces small reddish flowers that emerge several inches above water on a spike grown from the tip of the stem. The leaves of are limp when held out of water.

Habitat Characteristics:
Can grow in a wide variety of habitats/conditions. Ponds, lakes, reservoirs, and slow flowing rivers and streams. Will grow in shallow or deep water, fresh or brackish water, a wide temperature range, as well as a pH from 5.4 to 11. Does well in waters that have had some sort of disturbance like intense plant management, overabundance of nutrients, or extensive motorboat use. Grows best in fine textured inorganic soils where it can get plenty of sunlight.

Behavior:
Each plant capable of making over 100 seeds but germination of seeds rarely takes place. New shoots begin to grow from the overwintering root crowns when water temperature reaches about 60o F in the spring. Growth is rapid and when the plant nears the water's surface it will branch out creating a canopy. Fast growth and topped out canopy generally occurs before native species peak in growth. Flowering generally occurs in July. Autofragmentation usually occurs after flowering. Plants die back to the roots in the fall. These roots store carbs in order to initiate rapid growth in the spring.

Control Methods:
Prevention... Mechanical: Only be considered if it is widespread & all available niches have become occupied by plant. Important bc mech. techniques usually result in fragmentation which help plant spread. Cut stems can also branch which can result in even denser plant beds if harvesting does not occur freq. through growing season. Harvesters & hand cutting are most common mechanical removal methods. All fragments must be collected and disposed of properly (composting, burning, burying, or trash disposal). Habitat Alteration: Winter lake drawdown. Biological: "environmentally friendly". Should be target specific and not cause harm to unintended species. Most common biological control used is grass carp or white amur. Plant pathogens have also been sought out as a biological control. Lab research has shown that fungus Mycoleptodiscus terrestris educes plants biomass. Most effective biological control method has been the North American weevil, Euhrychiopsis lecontei. This seems to only attack milfoil and causes a high level of damage to the plant. Adults feed on stems and leaves of plant and larvae bore into stem causing extensive damage. Chemical: Active ingredient Fluridone has been used at low rates to selectively control Eurasian watermilfoil. Aquatic herbicides containing Triclopyr or 2,4-D have also proven effective.
Giant Reed (Arundo donax)
Life History:
Asian native and was cultivated for thousands of years in southern Europe, northern Africa, and the Middle East. It was introduced
into southern CA as an ornamental, and was used as
an erosion control species along drainage ditches.

Distribution:
Arkansas and TX to CA, where it is found throughout the state, and in the east, from VA to KN and Missouri and generally southward.

Anatomy & Physiology:
Tall, perennial grass that can grow to over 20 feet in height. Its fleshy, creeping rootstocks form compact masses from which tough, fibrous roots emerge that penetrate deeply into the soil. Leaves are elongate, 1-2 inches wide and a foot long. The flowers are borne in 2-foot long, dense, plume-like panicles during August and September.

Reproduction:
Primarily vegetative, through rhizomes which root and sprout readily. Little is known about the importance of sexual reproduction in giant reed, or about its seed viability, dormancy, and germination, and seedling establishment.

Habitat Characteristics:
Moist places such as ditches, streams, and riverbanks, growing best in well drained soils where abundant moisture is available. It tolerates wide variety of conditions (high salinity) & can flourish in many soil types from heavy clays to loose sands. Disturbed and undisturbed streambanks, desert springs, flood plains, drainages, irrigation waterways, on sand dunes, and in wetland or riparian areas.

Control Methods:
Mechanical control (e.g., repeated mowing) may be somewhat effective, but if small fragments of root are left in the soil, they may lead to reestablishment. Chem: Systemic herbicides, such as glyphosate may be applied clumps after flowering, either as a cut stump treatment or as a foliar spray. Fire: Prescribed burning, either alone or combined with herbicide applications, may be effective if conducted after flowering.
Hydrilla (Hydrilla verticillata)
Life History:
Dioecious form of Hydrilla is believed to originate from the Indian subcontinent, specifically the island of Sri Lanka, although random DNA analysis also indicates India's southern mainland as a possible source location. The monoecious form is believed to have arrived on our shores from Korea. The dioecious strain of H. verticillata was imported as an aquarium plant in the early 1950s. Discarded (or intentionally planted ) colonies were found in canals in Miami and Tampa shortly after. Monoecious strain was introduced separately decades later in the Potomac Basin.

Distribution:
Stem fragments, although turions (buds) and subterranean tubers also play an important role. Main means of introduction is as castaway fragments on rec. boats & trailers and in their live wells. New colonies can often be found near boat ramps as such stem pieces become rooted in the substrate). Boat traffic thru established populations can shatter and spread it throughout the waterbody, similar to the spread of Eurasian watermilfoil.

Anatomy & Physiology:
Submersed freshwater herb. Being an invasive non-native weed, it often forms dense stands from the bottom to the top of the water, sprawling across the surface, although it may also be found as detached drifting mats. Pointed, bright green leaves about 5/8 inches long. The leaves grow in whorls of 3 - 10 along the stem, 5 being most common. The margins of the leaves are serrated. Thin stalks from stem end in a single, small, floating white flower at water's surface. Key IDing feature is presence of small, dull-white to yellowish, potato-like tubers which grow 2 to 12 inches below surface of sediment at ends of underground stems. Tubers form at end of growing season & serve to store food to allow it to overwinter.

Habitat Characteristics:
Often a contaminant on popular watergarden plants and may be unwittingly transported and established in private ponds in this manner. As with most invasive aquatic plant species, Hydrilla is a very opportunistic organism and can often be found taking over waters that have had populations of Eurasian watermilfoil chemically removed without a management plan for reestablishing native vegetation.

Control Methods:
Prevention... Power weed cutters mow underwater weeds below water surface and gather them onto a conveyor. Mechanical harvesting needs to be performed several times per growing season. Since the mowing and removal process cannot capture every single fragment of stem and leaf, water and wind currents moving away from harvest area can easily carry fragments to areas of a waterbody and result in new pops. Chemicals are easier to apply, but also costly. Herbicide spraying works best in small, enclosed bodies of water, and does not work at all in larger bodies, or in moving water.
Biological control insects as part of efforts to control Hydrilla have been attempted. Invasives. Another method is the control of water levels. Large-scale, long-term water drawdowns. However, since new plants can grow from the buried tubers, regrowth can take place when water levels are allowed to return to normal.
Suction harvesting by divers using very strong vacuum hoses can be used to remove it from confined areas. However, regrowth can take place from the tubers during the next growing season. Any fragments that escape during vacuum activities can float away to root and start new infestations.
Purple Loosestrife (Lythrum salicaria)
Life History:
European origin, spread & degraded temperate North American wetlands since the early 1800s. Introduced both as a contaminant of European ship ballast and as medicinal herb for treatment of diarrhea, dysentery, bleeding, wounds, ulcers and sores.

Distribution:
By the 1830's, it was well established along New England seaboard. Construction of inland canals & waterways in the 1880's favored expansion of the plant into NY and the St. Lawrence River Valley. The continued expansion of it coincided with increased development and road systems, commercial dist. of the plant for horticultural purposes, and regional propagation of seed for bee forage. As of 1996, it is found in all contiguous states (except FL) and all Canadian provinces.

Anatomy & Physiology:
Perennial, emergent aquatic plant. 30 -50 herbaceous, erect, annual stems rise about 9 feet tall, from a persistent perennial tap root and spreading rootstock. Short, slender branches spread out to form a crown 5 ft wide on plants. Somewhat squarish stems are 4 to 6 sided, w/ nodes evenly spaced. Stems submerged under water develop aerenchyma tissue characteristic of aquatic plants. The stalkless leaves can be opposite or opposite w/alternating pairs at 90 degree angles or sometimes in whorls of 3, near the base. Upper leaves & floral bracts can be alternate. Leaves are one ½ to 4 inches long, wider and rounded or heart-shaped at the base. Leaf shape varies from lanceolate to narrowly oblong, and is sometimes covered w/fine hairs. Variability in pubescence & leaf shape is influenced by light levels - leaf area increases and fine hairs decrease w/ lower light levels.
Magenta flowering stems end in a 4-16 inch flowering spike. Flowers appear from July to early October. The flowers are in pairs or clusters of the upper leaf axils. Each flower is complete, containing 5 - 7 petals, w/ the same number of sepals as petals, and 2x as many stamens as petals. Typical flowers have 6 sepals, 6 petals and 12 stamens. Ovary is superior, w/ 2 fused carpels. The narrow, wrinkled petals are from 1/4 to 5/8 in long. Petal color can range from white to pink to red to purple. Fruit is a 2-valved capsule enclosed in the pubescent calyx. Pollen grain color & size varies. Each flower exhibits one of three style lengths (tristylous). Flowers are short-styled (w/medium and long stamens), medium-styled (w/short and long stamens), or long-styled (w/short and medium stamens). Individual plants produce 1 style-type.

Reproduction:
Seed Production and Dispersal: A mature plant can produce 2.7 million thin-walled, flat seeds. Some seeds sink in the water, and resurface after germination. Water dispersal includes floating seedlings and floating ungerminated seeds. The seeds are small and light enough for wind dispersal. Most dispersal is down slope, (not downwind). Transport through wetland mud by animals, humans, boats, or vehicles. Spread also occurs when seeds eaten. Also vegetatively. Disturbance to plant (stomping/ breaking underground stems, or breaking off stems or roots during incomplete plant removal) initiates bud growth.

Habitat Characteristics:
Freshwater & brackish wetlands. Successful colonizer & potential invader of any wet, disturbed sites in North America. Can sometimes grow in upland sites.

Control Methods:
No effective method is available to control it. Uprooting plant by hand & ensuring removal of all vegetative parts can eliminate it. Water-level manipulation, mowing or cutting, burning, and herbicide application. These are costly, require continued long-term maintenance and are non-selective and environmentally degrading.
Biological Control: 4 host specific insect species have been released in the US. These species are a root-mining weevil, two leaf-eating beetles, and a flower-feeding weevil.
Water Hyacinth (Eichhornoa crassipes)
Life History:
Native of South America considered a major weed species in more than 50 countries. Introduced into FL in the 1880s & covered more than 120,000 acres of public lakes and navigable rivers by the early 1960s. .

Distribution:
Origin in tropical Brazil, but has become naturalized in many warm parts of the world: Central America, North America, Africa, India, Asia, Australia, and New Zealand. Present in the states of the southeast U.S., and CA, Hawaii, and the Virgin Islands.
Has been reported in NY, KN, TN and Missouri "where plants escape summertime cultivation but do not persist through the winter...it is annually stocked in farm fish ponds in southern Arizona and southern Delaware," but has not become established in the natural systems of these states.

Anatomy & Physiology:
Floating plant with thick, glossy, round leaves, inflated leaf stems, and very showy lavender flowers. Sometimes found stuck in mud, appearing rooted, and is rarely found as a single plant

Reproduction:
Free-floating plant that gets its nutrients from water from dangling roots. Reproduces by seeds & vegetatively thru daughter plants that form on rhizomes and produce dense plant beds. Can form impenetrable mats of floating vegetation. Individual plants break off the mat and can be dispersed by wind and water currents. A single plant can produce as many as 5,000 seeds and waterfowl eat and transport seeds to new locations. Seedlings are common on mud banks exposed by low water levels.

Habitat Characteristics:
Can survive freezing conditions

Behavior:
Because of aggressive growth rate, it is illegal to possess in FL w/o a special permit. Growth rate is among highest of any known plant. Pops can double their size in as little as 2 weeks.

Control Methods:
Prevention (people not dumping old plants). Harvesting, application of aquatic herbicides, and biological control agents.

Laws & Regulations:
Illegal to possess (true of most if not all invasives).
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