Utricularia foliosa L.: Bladderwort. Lentibulariaceae (bladderwort family).
Native perennial. This carnivorous plant traps insects, crustaceans, and other small aquatic animals in tiny pouches called bladders. The plant does not have true roots or leaves; it floats freely in the water and most of its parts are coated with a jelly-like substance. The stem tissue is strap-like, thick and flattened; stems can be over 0.4 in (1 cm) wide and elongate to over 3 ft (90 cm). The plant forms dense feathery branches made up of numerous thread-like divisions; a portion of these carry the little green bladders, thickly scattered along the side branches. The spherical bladders have a very short stalk and an opening on one side. Yellow flowers are carried above the water, with up to 20 on the stiff leafless flower stalk 0.4 - 1.2 in (1 - 3 cm) long. Plants can be found in large stands.
Ceratophyllum demersum L.: Coontail, hornwort. Ceratophyllaceae (hornwort family).
Native perennial. This plant grows submersed in slow-moving water; it does not attach firmly in the substrate as it lacks true roots. It is able to colonize water to 18 ft (5.5 m) deep. The light-colored stems are slender and brittle and they branch freely, although branches are limited to one per node. Plants multiply vegetatively when broken pieces of stem grow to whole plants. The stalkless leaves occur in brush-like whorls of as many as 12; they can be up to 1.25 in (3 cm) long. Individual leaves consist of very slender segments that fork one or more times; these segments have pointed ends and toothed edges that make the leaves feel rough. The rather stiff leaves curve in toward the stem when removed from the water but do not flatten or collapse completely. The denser arrangement of leaf whorls near the tips makes the stems resemble bushy raccoon or fox tails, particularly when the wet plant is held tip-down. Inconspicuous flowers emerge at nodes. The long-branched stems provide wildlife habitat, but the plants can aggregate to form areas of dense matted growth, and the plant sometimes becomes a nuisance to a range of water uses.
Elodea canadensis Rich. in Michx.: Elodea, American or Canadian elodea, waterweed. Hydrocharitaceae (frog's bit family).
Native perennial. Rooted in the substrate, vegetative reproduction is by stem fragments. Stems are very slender and brittle. The leaf is stalkless; the blade is linear, 0.4 - 0.8 in (1 - 2 cm) long, narrowing to a pointed but not sharp tip, with a single main vein. There are tiny teeth on the leaf margins (may require magnification to see). Leaves are almost always in whorls of 3 (occasionally up to 7), but the lowest leaves on the stem can be alternate, opposite, or whorled. Long slender flower stalks emerge from a tubular structure, and the flower floats on the surface. Elodea differs from hydrilla and egeria in having smaller plant and leaf size, consistent whorls of 3 leaves, and a lack of spines on the lower part of the underside of the midvein. Elodea feels smoother than hydrilla. While elodea can produce dense colonies and requires control in certain areas, it does not often become a nuisance.
Myriophyllum spicatum L.: Eurasian water milfoil, spiked milfoil. Haloragaceae (watermilfoil family).
Non-native perennial. Submersed except for emergent flower spike; rooted in substrate and growing in still or flowing water. The spongy, stretchy, reddish stems grow to 10 ft (3 m) long and branch frequently, forming dense canopies at the surface. Rather stiff, feather-like leaves, to 2 in (5 cm) long, are arranged 4 to a whorl. The slender leaf divisions are almost paired on either side of the central midrib; these divisions extend out and then up toward the leaf tip where their ends form a blunt or squared-off edge across the top of the leaf, rather than a point. The number of leaflet divisions per side of an individual leaf is usually more than 12 to 14. In comparison, native Myriophyllum species usually have fewer, from 5 to 12, divisions per side. The emergent flower spike has whorls of inconspicuous flowers spaced at intervals. This plant reproduces rapidly within a season from easily-rooted stem fragments. It also forms dense clusters of leaves at some branch tips; these winter buds can detach, fall to the substrate, and give rise to new plants in spring. Eurasian watermilfoil's thick surface canopies cut off light and oxygen to the lower water levels beneath it, and this competition eliminates native submersed plants. It is an extremely noxious weed and has devastated many aquatic environments.
Cabomba caroliniana Gray: Fanwort. Cabombaceae (water-shield family).
Native perennial. Rooted submersed plant with many long, branched, flexible, spongy stems and dense, feathery foliage; it occurs in 3 - 10 ft (0.9 - 3 m) of water. The stem has pairs of finely-cut, pom-pom-like leaves at each node. The leaf stalk is flexible and gives rise to a leaf blade consisting of numerous narrow, flat divisions that branch several times. The ends of these divisions are blunt or squared-off; the leaf forms a characteristic fan-shaped semi-circle when it is spread out flat. Leaves may have purple or reddish coloration on the underside. Flowers are white to pale purple, about 0.5 in (1.25 cm) wide, and are borne at or a little above the water surface; they may be accompanied by small, narrow, diamond-shaped leaves whose stalks are attached in the center of the lower surface as in the related watershield, Brasenia schreberi. Fanwort's dense structure can cause access and water flow problems where population numbers are high.
Zannichellia palustris L.: Horned pondweed. Zannichelliaceae (horned-pondweed family).
Native perennial. Submersed plant; branches freely from slender rhizomes in the substrate and grows to 3.3 ft (1 m). It has very slender, flattened, grass-like stems and leaves. Leaves are opposite (unlike Potamogeton species), sometimes whorled, with 2 to several emerging per node. The stalkless blade is flat, strap-like, 1 - 4 in (2.5 - 10 cm) long, with smooth edges. A thin sheathing stipule at each node surrounds the stem and leaf bases. Flowers and later fruits are borne underwater in short clusters at the nodes. The inconspicuous flowers are inside small bracts, 0.1 in (2.5 mm) long. The curved fruits are hard, rough-surfaced and ridged, 0.125 in (3 mm) long, and topped by a prong or horn about half as long as the fruit itself. The plant can form mats at the surface.
Hydrilla verticillata (L. f.) Royle: Hydrilla. Hydrocharitaceae (frog's bit family).
Non-native perennial. Submersed, roots in substrate; branches freely from base. Slender rhizomes in substrate produce small starchy oval tubers at their tips. The thin stems can elongate to over 20 ft (6 m). From 2 to 8 branches emerge at each branching node; plants can grow with minimal branching to reach the surface and then branch explosively to form dense mats. Leaves occur in whorls around the stem, usually at least 4, but the number varies with position, from 2 to 3 at the base of the stem, and up to 8 per whorl at the tip. The stalkless leaf is linear oval, widest in the middle and narrowing to the base, to 0.6 in (1.5 cm) long, with a sharply pointed tip. The leaf margins are toothed; the single main vein on the underside of the leaf is slightly ridged, or keeled, and has teeth all along it. These teeth or spines are usually visible without magnification and make the plant rough to the touch. Insignificant flowers, less than 0.25 in (6 mm) wide, are carried to the surface on threadlike stalks. Vegetative reproduction occurs from stem fragments and turions, which are plump, bud-like clusters of crowded leaves produced at nodes on the stems. Colonies can cover many acres. A major noxious weed, able to out-compete all other submersed aquatic plants, hydrilla hinders aquatic wildlife and all water uses and activities.
Hygrophila polysperma (Roxb.) T. Anders.: Hygrophila, East Indian hygrophila, Indian swampweed, Miramar weed. Acanthaceae (acanthus family).
Exotic perennial. A robust rooted plant growing densely in slow-moving water to a length of 6 ft (1.8 m). Can generate unattached but solid-appearing mats that float just below the surface The plant is mostly submersed but stem tips can emerge to a height of about 6 in (15 cm). Stems change from cylindrical when underwater to almost four-square when above water; they are brittle, and root and branch readily at the nodes. Leaves are opposite, oval, broadly pointed, 1.5 in long by 0.5 in wide (4 by 1.25 cm), with short stalks when submersed and none when emergent. Leaves contain tiny granules of calcium carbonate (cystoliths) that feel rough. Flowers are two-lipped, white to light blue, but inconspicuous, borne on the upper stem. Small cylindrical fruits split apart to shed a couple of dozen seeds each. Invasive and weedy, forming dense mats that hinder water use and aquatic wildlife, this species is listed as a U.S. Federal noxious weed. Note that the native lake hygrophila is almost entirely emergent, with larger leaves.
Najas spp.:Naiads, water nymphs. Najadaceae (water-nymph or naiad family).
Native and non-native annuals. Rooted in the substrate; roots emerge from seed or nodes on the stem. The long slender green stems branch frequently, grow to several feet, and extend horizontally at the surface. Leaves are opposite, sometimes in whorls, without stipules or sheaths (compare to the alternate leaf arrangement and stipules of Potamogeton spp.). The small leaves are narrow, linear, and strap-like, 0.25 - 1.5 in (0.6 - 3.75 cm) long; each blade has a widened base that clasps the stem, meeting the leaf base on the opposite side. Leaves are more or less conspicuously toothed along their margins. Leaves are green to reddish-purple; the midvein and/or underside may be more reddish than the rest of the blade. Inconspicuous, single, stalkless flowers are borne in the angle between the leaf bases and the stem; one-seeded pointed fruits are produced and seed production is usually high. These species are often a component of varied submersed plant communities.
Myriophyllum sibiricum Komarov: Northern milfoil. Haloragaceae (watermilfoil family).
Native perennial. A submersed plant, growing to 10 - 14 ft (3 - 4 m); rhizomes root in sediment in still or moving, preferably clear, water. Unlike M. spicatum, it does not usually form a canopy at the surface. The stem is stouter than in M. spicatum, and the whorls of 3 to 4 leaves are spaced wider apart on the stem. The feather-like leaves are made of up thread-like divisions arrayed flat along a central midrib; leaves are up to 1.6 in (4 cm) long. The number of leaflet divisions is usually less than 14 per side on an individual leaf, fewer than in M. spicatum. These divisions are longer at the leaf base and shorter at the tip so the overall outline of a flattened leaf is pointed and lance-shaped. The flower stalk emerges above water. Plants can reproduce via rooted stem fragments and by winter buds, which are dense clusters of leaves formed at branch tips. Provides worthwhile habitat and seldom reaches nuisance levels.
Myriophyllum aquaticum (Vell.) Verdc.: Parrotfeather. Haloragaceae (watermilfoil family).
Exotic perennial. Grows from rhizomes in shoreline mud or in water depths to 3.3 ft (1 m), often with all or most of the plume-like plant emergent. Can form large dense colonies and compete with other emergent aquatic plants. Stems can be reddish and up 6.5 ft (2 m) long. Emergent foliage is soft and feathery, a striking light- to gray-green, with a waxy-looking bloom. The rather stiff emergent leaves are in whorls, 3 to 6 leaves around the stem, and up to 2 in (5 cm) long. The individual leaf resembles a tiny narrow feather; it is made up of 20 or more paired leaf divisions that are shorter than in most other milfoils. Underwater leaves are similar, but more flexible and a little longer. Inconspicuous flowers can occur around stems at base of leaves, but are not often produced. This species spreads by underground stems or from rooted stem pieces, and is able to produce dense stands that hinder water use and degrade habitat.
Tape Grass, Eel Grass, Water Clery
Vallisneria americana Michx: Tape grass, eel grass, water-celery. Hydrocharitaceae (frog's bit family).
Native perennial. Plants are rooted in the substrate and consist of a cluster of stalkless, ribbon-like leaves that emerge from a compressed, hidden stem. The leaves, crisp to spongy and flexible, are 1 - 2 in (2.5 - 5 cm) wide and up to 7 ft (2.1 m) long, with one or both surfaces slightly curved; the tips are broadly pointed. They may extend horizontally when they reach the surface. Leaves differ from those of bur-reed, Spargania americanum, in lacking a prominent midrib or keel but having minute teeth along the margins. Individual cross-veins, perpendicular to the long edges, do not extend across the whole leaf width. Long slender flower stalks grow from the base of the leaves, each carrying a single tubular female flower to the surface for pollination; the stalks then coil to pull the flowers back underwater where the elongated fruits ripen. Vegetative reproduction is common via daughter plants produced on slender horizontal stolons. This plant is very valuable to wildlife but may require control in certain situations.
Myriophyllum heterophyllum Michx.: Variable-leaf water milfoil, two-leaf milfoil, foxtail. Haloragaceae (watermilfoil family).
Native perennial. Rhizomes buried in the substrate produce roots and stout reddish stems (0.1 in, 3 mm, thick). Stems grow to 6 ft (1.8 m) under water; upon reaching the surface they can emerge up to 6 in (15 cm). The submersed and emergent stems have distinctly different leaf forms. Underwater leaves are arranged in close whorls of usually 5 to 6. They are up to 2.5 in (6 cm) long and consist of very slender, soft, thread-like divisions projecting on either side of a central midrib; there are from 6 to 14 of these leaflet divisions per side. The underwater stem forms a dense tuft at its tip and resembles a soft bottlebrush. As the stem reaches the surface it changes its growth pattern to become a stout emergent flower-spike carrying an entirely different type of leaf (actually a bract). These emergent leaves are stalkless, wedge-shaped, stiff, and pointed, with variably-toothed margins; they are up to 1.2 in (3 cm) long. Inconspicuous flowers are borne just above the bases of these leaves. The plant can form dense growth, rooting from stem fragments, and reaches nuisance levels in some regions.
Zosterella spp (Jacq.) MacM.: Water stargrass Pontederiaceae (pickerelweed family).
Native perennial. Submersed rooted plant found in quiet water, streams, shallow water and mudbanks. Roots are long and slender, and are formed at the nodes of the slender branching stems. Grass-like, linear, stalkless leaves are 4 - 6 in (10 - 15 cm) long and arise alternately on the stem. Leaves do not have a prominent midvein. The base of the leaf enlarges to clasp or almost surround the stem like an open tube; this structure has two upward-pointing tips. A single star-shaped yellow flower, made up of 6 strap-like petals, arises from the end of a long slender stalk and is held at the surface. This plant produces dense stands and can be a weed problem.
Waterweed, Brazilian Elodea
Egeria densa Planch.: Waterweed, egeria, Brazilian elodea, anachris. Hydrocharitaceae (frog's bit family).
Non-native perennial. Submersed and rooted in the substrate; multiplying from stem fragments. The firm, crisp stem has relatively few branches and grows to 6 ft (1.8 m). Leaf arrangement is most often in whorls of 4, although groups of 3 to 6 are found; leaves at the base of the stem can be opposite. At intervals along the stem two whorls occur very close together, like one node with twice the usual number of leaves; these double whorls are the only ones that produce branches (one to two branches each) and adventitious roots. Leaves are bright green, thin, shiny and almost translucent. The narrow linear blade is stalkless, up to 1.2 in (3 cm) long and 0.2 in (5 mm) wide, with a single main vein and pointed end. Tiny teeth are found on the leaf margins and toward the tip on the midvein of the underside of the leaf (may require magnification to see). Three-petaled white flowers, up to an inch (2.5 cm) across, are held at the water surface. Compared to hydrilla, a close relative, egeria feels softer and smoother due to the fineness of its foliar teeth. The axillary buds that give rise to side-branches in egeria are large, stiff, and sharply pointed; they are very noticeable when running one's hand down a stem. Widespread and invasive, multiplying vegetatively and creating very dense stands, this is a major nuisance species, obstructing boat traffic and hindering water flow and use.