Alternanthera philoxeroides (Mart.) Griseb.: Alligator weed. Amaranthaceae (pigweed family)
Exotic perennial. Rooted in submersed substrates, at shoreline, or in moist to dry soil. Herbaceous; forms dense stands of slightly fleshy growth. Stems are pinkish, usually hollow, upright to trailing, to 3.3 ft (1 m) long; on floating portions of the plant they can be swollen or inflated. Leaves are opposite, 2 - 5 in (5 - 12.5 cm) long, linear, oval, pointed to rounded at the top, and tipped with very small spines; they have distinct pale midveins and mostly smooth margins. Where the two narrowed leaf-bases join around the stem there is a small tuft of hairs. The stems form thickened joints at the leaf nodes; these readily produce roots, contributing to the plant's ability to spread. Flowers are interspersed with stiff bracts in white, round, clover-like heads borne singly on stalks in leaf axils. This plant can hinder access to waterways, and slow water movement.
Bacopa caroliniana (Walt.) Robins: Blue-hyssop, lemon bacopa, Carolina water-hyssop. Scrophulariaceae (snapdragon family).
Native perennial. Emergent growth from rhizomes rooted in substrate of moist shorelines or where water is shallow. It can grow completely submersed in neutral to acidic water. Can crowd to form dense mats 12 in (30 cm) tall. The plant's tissues are succulent to fleshy and give off a lemon odor when crushed. Leaves are small (0.2 - 0.8 in; 0.5 - 2 cm), opposite, without leaf stalks, oval to wedge-shaped, with bases that partially clasp the slightly hairy stems. The leaves are covered with clear dots (glands) that produce the characteristic citrus smell. The 4- to 5-petaled blue flowers emerge singly on short stalks among the leaves at the top of the stem.
Mayaca fluviatilis Aubl.: Bog moss. Mayacaceae (bogmoss family).
Native perennial. Can be found in moist soil, as an emergent along shorelines and in shallow water, or fully submersed in water to 6.5 ft (2 m) deep. The emergent plants resemble shining clubmoss; bog moss, however, produces true flowers. On land, the leafy stems can be upright, or run along the ground and then turn or branch upwards, to at most 2 ft (60 cm). Stems of emersed plants are covered with short narrow pointed leaves arranged in a close spiral. These leaves are lance-shaped to linear, pointed at the tip and up to 0.4 in (1 cm) wide at the base; leaf midveins can be seen. Submersed plants usually have more flexible, much longer stems, up to several feet; their leaves are slender and thread-like, 0.25 in (0.6 cm) long. The 3-petaled flower is borne singly near the emersed stem tip on a slender stalk; it can range from purple to white. The flower stalk elongates as the fruit matures. Emergent plants can become densely packed.
Sagittaria lancifolia L.: Bulltongue arrowhead, duck potato. Alismataceae (water-plantain family).
Native perennial. Can grow in shallow to fairly deep water, or in very moist soil. The strong, spongy leaf stalks emerge fan-wise from seed or from the thick, knobby rhizome to a height of 30 in (80 cm), holding the robust lance-shaped leaves upright. Leaves lack the arrowhead shape of many Sagittaria; there are no leaf-base extensions on either side of the stalk. The firm leaf blade is a long slender oval, 10 - 25 in (25 - 64 cm) long and 1.5 - 4 in (3.75 - 10 cm) wide, pointed at the tip, and tapering gradually into the leaf stalk at the base. There is a ridged or keeled midrib down the center of both sides of the leaf blade; 2 or 3 additional main veins may be seen paralleling this one. The showy white flowers are borne on tall (to 5 ft; 1.5 m) leafless stalks, usually in whorls of three. Flowers have three short broad petals attached by a narrow strip or "claw" of tissue to a center of many thread-like yellow parts. The flattened-sphere or button-like fruits, indented in the middle, are firm and rough textured. Large starchy corms are produced at the ends of rhizomes.
Scirpus spp. Bulrush species. Cyperaceae (sedge family).
Native annuals or perennials. Grow from rhizomes to form clumps of slender, smooth, jointless stems arising above water or lower marsh plants. Rarely grows submersed. Many species are tall, growing to 10 ft (3 m), while others are as short as 6 in (15 cm). Stems are often round but can be edged or three-angled (triangular in cross-section); they usually have pith. Leaves are found at the base or lower stem; they consist of a cylindrical sheath that entirely encloses the stem and that usually gives rise to a linear blade of varying length; some species have leaf sheaths but lack blades entirely. A cluster of flowers, often hanging from slender stalks and resembling a brown club or plume, emerges from the top, or from one side of the upper third, of the stem. Individual flowers are grass-like rather than showy, variable in shape and usually made up of brown or green bracts or spikes.
Spargania americanum Nutt.: Bur-reed. Sparganiaceae (bur-reed family).
Native perennial. Grows emersed in shallow water, or submersed in deep water, where the leaves float along the surface; water bodies can be still or flowing. Slender rhizomes are produced in the substrate, giving rise to stout stems and spongy foliage resembling cattail. Plants to 24 - 40 in (60 - 100 cm) tall; leaves arise from the base and higher up along the stem, over-topping the stem apex where flowers emerge. Leaves are spongy, long and slender, to 3 ft (90 cm) long and 0.8 in (2 cm) wide. They have a channel running down the middle of the upper surface and a distinct V-shaped keel down the midrib on the underside; cattail and Vallisneria lack this keel. The leaf margins are smooth, without teeth. The upper, flowering, portion of the stem tends to angle back and forth at each flower node, forming a characteristic zig-zag. The shaggy white spherical flowers are set close against the stem. The fruits are also spherical, covered with short, spiky, wedge-shaped nutlets; they look similar to a sweet-gum bur. This plant produces corms. Its thick colonies are useful to wildlife.
Typha latifolia L.: Cattail, tule. Typhaceae (cattail family).
Native perennial. Grows in shallow water or very moist soil from thick rhizomes to form dense stands over large areas in ditches, wetlands, and water margins. Stem and leaves upright, to over 8 ft (2.5 m) tall. The stiff, cylindrical, jointless stem emerges out of the clasping sheaths that form the bases of the leaves. The long, narrow, strap-like, spongy leaves are bright green and smooth, with tapering tips; the front surface is almost flat and the back is flat or slightly curved. The stem terminates in a spike carrying two types of flowers: the velvety brown cylinder, to 1 ft (30 cm) long, is made up of numerous, densely packed female flower tufts; the upper portion consists of more shaggy male flowers. These latter often disintegrate and fall off before the female flowers do. Although the starchy rhizomes are edible and form a wildlife food, the leaves are said to be poisonous to livestock. Dense stands out-compete other plant species in aquatic areas, reducing desirable habitat; colonies can fill in open water and degrade wetlands.
Large Flower Primrose Willow
Ludwigia uruguayensis (Camb.) Hara (formerly Ludwigia hexapetala, Ludwigia grandiflora): Large flower primrose willow; water primrose. Onagraceae (evening-primrose family).
Native perennial. A shoreline and water margin plant that forms dense mats, rooting from leaf nodes into moist soil or water and growing up to 3 ft (90 cm) in height. When overwintering and before flowering the plant has a compact rosette form, with shiny, mostly smooth, bright green leaves on very short stems. These rosette leaves are rounded ovals with well-marked mid- and side veins. As plants approach flowering, the stems lengthen, become more hairy, and produce leaves of another type; these are alternate on the stem, very narrow, pointed, and up to 4.75 in (12 cm) long. The showy flowers, 1.5 in (3.75 cm) wide, are borne singly, having usually 5 (sometimes 6) bright yellow petals; their stalks and sepals are hairy. The fruit is a 5- to 6-ridged cylinder and has numerous cube-shaped seeds. Considered a nuisance species in many areas, water primrose's aggressive dense growth clogs waterways and interferes with shoreline activities.
Pontederia cordata L.: Pickerelweed. Pontederiaceae (pickerelweed family).
Native perennial. This plant produces stout upright emergent stems and leaves from a thick rhizome or root base, growing to 3 ft (90 cm) in water or along water margins in very wet soil. Large, dense stands are common where it is established. The leaf blades are up to 12 in (30 cm) long and 6 in (15 cm) wide; they vary from broad to narrow. They are usually heart-shaped and indented at the base, with rounded basal lobes; however, they can be lance-shaped and tapering, with no basal lobes. Leaf blades are thick, smooth and leathery, evenly covered with numerous parallel veins. The leaf stalks are usually shorter than the blade; they form a tube-like sheath that almost completely encloses the stem. The showy flower spike is held above the leaves at the top of a stout stem; flowers are numerous, small, purple to blue (sometimes white), each with a yellow spot in the middle of the upper petals. This plant can create dense stands; it is valuable for wildlife but occasionally reaches nuisance proportions.
Hydrocotyle umbellata L.: Water pennywort, marsh pennywort, giant floating pennywort. Apiaceae (carrot family).
Native perennial. Low-growing and spreading, with slender, smooth stems that run horizontally on or in moist soil or water; the whole plant can grow floating. Roots arise from nodes on the stem. Leaves are borne upright on stalks up to 12 in (30 cm) long, emerging from the running stem. Leaf blades are almost circular, edged with slight notches and one deeper indentation, and are up to 2.75 in (7 cm) across. Leaves are shiny and leathery, with a pale spot in the central shallow depression where the leaf stalk attaches to the underside. Veins radiate out from this point. Whitish flowers occur in open spherical heads borne on stalks that arise from the horizontal stems. These umbels are usually held above the leaves and are quite showy. This is the largest of the pennyworts.
Colocasia esculenta (L.) Schott: Wild taro, elephant-ear. Araceae (arum family).
Exotic perennial. The plant's stout leaf-stems emerge to a height of 1.5 - 4 ft (0.45 - 1.2 m) from a large round, roughly-ridged, brown corm (the taro root); they produce dense clumps in shallow water or moist or swampy soil. The large leaves, 10 - 24 in (25 - 60 cm) long, are arrowhead-shaped, with long rounded basal lobes; leaf margins are wavy. Midveins from the main blade and the lobes form a 'Y' and the leaf stalk attaches to the underside of the blade where these veins meet. Small flowers are borne on a short spike within a slender, yellow, leaf-like structure. Vegetative reproduction is common, from corms produced on underground stems. The raw leaves and fleshy root contain irritating calcium oxalate crystals that can cause poisoning. While these plant parts are used for food in certain areas of the world, they require thorough cooking.