Types of Texas Lake Weeds

Algae

Filamentous Algae

Filamentous Algae Known as “pond scum”, filamentous algae forms greenish mats upon the water’s surface. It typically begins its growth along the edges or bottom of the pond. Has a thread-like appearance, due to the fact that a series of cells join ene to end.

Planktonic Algae

Planktonic Algae: Planktonic algae are microscopic plants, usually suspended in the upper few feet of the water. It appears as a “pea green soup” or brownish in color.

Chara (Chara vulgaris)

Chara: Chara has a leaf-like structure around a hollow stem. Dense growth is attached, but does not root to the bottom. Mineral deposits on the weed surface can give it a gritty texture. Has a strong musky odor when crushed.

Submersed plants

Submersed plants are generally rooted at the bottom and are completely underwater. Submersed weeds are usually flacid and lack rigid cellular tissue. If any flowers are present, the may extend above the water surface.

Bushy Pondweed (Najas gracillima)

Bushy Pondweed: May be confused with Chara or Coontail. Unlike Chara, Bushy Pondweed does not have a musky odor when crushed. Leaves are narrow with tiny spines along the edges. Stems are slender with frequent branches. Leaves are densely concentrated at tips, with leaves oppositely attached or in groups of two or more at a node.

American Pondweed (Potamogeton nodosus)

American Pondweed: American pondweed is a perennial plant that has both floating and a few submerged leaves in an alternate pattern. The floating leaves are elliptical to oval 4 to 7 inches long and to 1 inche wide on long petioles. Submerged leaves are not abundant and are blade-like, somewhat transparent and smaller than floating leaves.

Cabomba (Fanwort) (Cabomba caroliniana)

Cabomba: (Also known as Fanwort) is multi-branched submerged perennial plant except for a few small (1/2 – 1 1/4 inches long) alternately arranged elongated floating leaves. The submerged leaves are opposite, attached by a single petiole, but above the petiole form a finely divided “fan-shaped” leaf. Fanwort has a small (1/2 to 3/4 inch diameter) white to pink flower which arises from the tip of the stem and stands slightly above the waters surface.

Coontail (Ceratophyllum demersum)

Coontail: Coontail has leaves with a serrated appearance. Spacing between leave whorls varies, with the whorls being crowded at tip. Branches fork repeatedly. Can be confused with Bushy Pondweed or Chara. Unlike Chara, Coontail does not have a musky odor when crushed.

Eurasian Watermilfoil (Myriophyllum spicatum)

Eurasian Watermilfoil: Eurasian watermilfoil is a perennial plant native to Europe, Asia, and Africa and was probably brought to the U.S. as an aquarium plant. Today it is considered one of the most aggressive and problematic plants in the U.S. because of the dense colonies which it forms. The stems are multi-branched, somewhat reddish in color, with gray-greenish feather-like leaves. The leaves are in whorls of 3 to 5 around the stem with each leaf divided into 12 or more pairs of thin thread-like leaflets. Reddish flowers are borne on leafless spikes that rise above the surface a few inches. Eurasian watermilfoil can spread from seeds or by fragmentation.

Hydrilla (Hydrilla verticillata)

Hydrilla: Hydrilla is a perennial plant that forms dense colonies and can grow to the surface in water over 20 feet deep. Hydrilla branches profusely and after reaching the surface it extends across it forming thick mats. Hydrilla can reproduce by fragmentation, from seeds, from turions (axilary buds), and from tubers. Leaves are blade-like about 1/8 inch and 3/8 inch long with small tooth margins and spines on the underside of the midrib which make them feel rough. Leaves are usually 4 to 8 in a whorl.

Hydrilla is native to Europe and Asia and was probably brought to the U.S. for the aquarium industry. It is considered a noxious pest because it grows so rapidly, out competing and eliminating native species, and forming surface mats that hinder recreation, navigation, and water intakes.

Hydrilla is often confused with the native Elodea or the non-native Egeria. Hydrilla has one or more teeth on the underside of the midrib, neither Elodea nor Egeria have these midrib teeth. The teeth make Hydrilla feel rough when drawn through your hand from base to tip. Flowers of Hydrilla are much smaller (1/4 inch in diameter) than Egeria.

Parrotfeather (Myriophyllum aquaticum)

Parrotfeather: Parrotfeather is a native of South America and was probably brought to the U.S. for the aquarium industry. It is a rooted, submerged perennial plant that usually grows in shallow water. Parrotfeather gets it name from the gray-green thickly bunched leaves that rise above the water. These exposed leaves are whorled and have frilly divisions that give it a feather-like appearance. Underwater leaves are similar but less dense. The stems are relatively stiff.

This plant is not native to North America but has naturalized in much of the United States. While it is not illegal to possess this plant in Texas it probably should not be introduced into new water bodies.

Emergent Plants

Emergent plants grow above the water in shallow areas of ponds, lakes, rivers, and irrigation ditches. They are generally rigid, and are not dependent on water for support. Many are not a true aquatic plant, but can survive in saturated soils, or submerged for a long period of time.

American Lotus (Nelumbo lutea)

American Lotus: Floating leaves are circular with stems attached to the center of the leaf underside. Flowers are solitary pale yellow and are made up of numerous petals.

Floating Heart or Banana Lily (Nympoides aquatica)

Floating Heart or Banana Lily: Banana lily is a perennial plant with leaves that arise from “banana-shaped” rhizomes on the long slender petioles. The floating leaves are 2 to 6 inches in diameter, kidney to heart-shaped, yellowish-green above and reddish-purple underneath, with obvious veins. Flowers are small, white, in clusters on short stalks that rise above the water’s surface. The fruits are capsule-like and contain many seeds. Late in the growing season clusters of fleshy, tuber-like roots form below the flowers.

Spatterdock or Cow Lily (Nuphar luteum)

Spatterdock or Cow Lily: Spatterdock is a perennial plant with leaves that arise from a large spongy rhizome. The leaves have a slit that makes them roughly heart-shaped, 8 to 16 inches long by 10 inches wide, and can float on the surface or stand above the surface on thick round (in cross section) stalks. Flowers are spiracle with 6 to 9 green sepals and yellow petals. Flowers can float on the water or stand above it. Fruits are oval with a flat top and greenish or yellowish in color. Spatterdock can spread from seeds or the rhizomes.

White Water Lily (Nymphaea odorata)

White Water Lily: The white water lily is a perennial plant that often form dense colonies. The leaves arise on flexible stalks from large thick rhizomes. The leaves are more round than heart-shaped, bright green, 6 to 12 inches in diameter with the slit about 1/3 the length of the leaf. Leaves usually float on the water’s surface. Flowers arise on separate stalks, have brilliant white petals (25 or more per flower) with yellow centers. The flowers may float or stick above the water and each opens in the morning and closes in the afternoon. The flowers are very fragrant. White water lily can spread from seeds or the rhizomes.

Water Shield or Dollar Bonnet (Brasenia schreberi)

Water Shield or Dollar Bonnet: Water shield is a perennial plant with relatively small, floating oval to elliptical leaves (to 5 inches in diameter) with no slit. Water shield has a distinctive gelatinous slime on the underside of the leaves and coating the stems. Leaves are green above while the underside of leaves and stems are reddish-purple. Stems attach at the center of the leaves. Flowers are small (9 1/2 to 3/4 inch), rise above the surface, are dull-reddish in color and consist of 3 to 4 sepals and petals. Water shield tends to be found in soft, acidic waters and can form large colonies.

Floating Plants

Plants with leaves that float on the surface of the water and have their roots planted in the bottom are part of the category. Free-floating plants that derive their source of nutrients directly from the water are also included. The key component is that water is critical for the support of the plant or its leaves.

Duckweed (Lemma minor)

Duckweed: Common duckweed is a very small light green free-floating, seed bearing plant. Duckweed has 1 to 3 leaves, or fronds, of 1/16 to 1/8 inch in length. A single root (or root-hair) protrudes from each frond. Duckweeds tend to grow in dense colonies in quiet water, undisturbed by wave action. Often more than one species of duckweed will be associated together in these colonies. Duckweeds can be aggressive invaders of ponds and are often found mixed in with mosquito fern or watermeal. If colonies cover the surface of the water, then oxygen depletions and fish kills can occur. These plants should be controlled before they cover the entire surface of the pond.

Common Salvinia (Salvinia minima)

Common Salvinia: Common salvinia is native to South American. It is a small free-floating plant that grows in clusters and develops into dense, floating mats or colonies in quiet water, undisturbed by wave action. The floating leaves of salvinia are more or less round (1/2 to 3/4 inch) with a distinct midrib along which the leaf may fold forming a cup-shaped appearance. Salvinias have stiff leaf hairs on the upper surface of the leaves. In common salvinia the leaf hairs have a single stalk that divides into four separate branches. Underwater the leaves are modified into small root-like structures. The entire plant is only about 1 inch in depth. Salvinias are ferns and have no flower. Common salvinia can reproduce by spores or by fragmentation and is an aggressive invader species. If colonies of common salvinia cover the surface of the water, then oxygen depletions and fish kills can occur. These plants should be controlled.

Giant Salvinia (Salvinia molesta)

Giant Salvinia: Giant salvinia is native to South American. It is a small free-floating plant that grows in clusters and develops into dense, floating mats or colonies in quiet water, undisturbed by wave action. The floating leaves of giant salvinia are oblong (0.5 to 1.5 inches long) with a distinct midrib along which the leaf may fold forming a compressed chain-like appearance. Salvinias have stiff leaf hairs on the upper surface of the leaves. In giant salvinia the leaf hairs have a single stalk that divides into four branches that reconnect at the tip, giving the hair a cage-like or egg-beater appearance. Underwater the leaves are modified into small root-like structures. The entire plant is only about 1 to 2 inch in depth. Salvinias are ferns and have no flower. Giant salvinia has sporangia but are thought to reproduce only by fragmentation. Giant salvinia can double in size in 4 to 10 days under good conditions. Giant salvinia is an aggressive invader species. If colonies of giant salvinia cover the surface of the water, then oxygen depletions and fish kills can occur. These plants should be controlled.

Water Lettuce (Pistia stratiotes)

Water Lettuce: Water lettuce is a free-floating plant with many spongy, dusty green simple leaves. The leaves are covered in very fine hairs and arranged in a spiral pattern from the center of the plant. The leaves are 1 to 6 inches wide and have large veins running their length. The flowers are seldom seen. Water lettuce is a very aggressive invader and can form thick floating mats. If these mats cover the entire surface of the pond they can cause oxygen depletions and fish kills. Water lettuce should be controlled so they do not cover the entire pond.

Shoreline Plants

Shoreline plants found primarily along the edge of water, which are grass-like in form, are included in this category.

Alligator Weed (Alternanthera philoxeroides)

Alligator Weed: Alligator weed is a perennial plant native to South America and 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.

Arrowhead (Sagittaria spp.)

Arrowhead: There are many species of Sagittaria but all are perennial plants that have arrowhead-shaped leaves. Usually leaves have 3 points giving it the arrowhead shape but some are narrow and almost grass-like. Arrowheads can grow in shallow water or in wet areas. Leaves grow in clusters from the base and can be from less than a foot tall to over 4 feet. Leaf petioles are long, often spongy and have a milky-like fluid if crushed. Rhizomes can be extensive and some species have large tubers off the roots. Flowers are borne on separate stalks above the water in whorls of three and are usually white to light pink with three petals. Arrowheads spread rapidly by seeds and extensive rhizomes

Bulrush (Scirpus spp.)

Bulrush: There are several species of bulrushes. Bulrushes are perennial grass-like plants and can grow to 10 feet tall in shallow water or in moist soils. Soft-stem bulrush can grow to 10 feet and grows in dense colonies from rhizomes. Soft-stem bulrush has a round (in cross section), light gray-green, relatively soft stem that comes to a point with no obvious leaves (only sheaths at the base of the stems). Flowers usually occur just below the tip of the stem.

Cattails (Typha spp.)

Cattails: Cattails have flat to slightly rounded leaves that twist slightly over their length and can grow to 5 or 10 feet in height. Flowers form a dense dark brown, cigar-shape at the end of spikes (called the catkin). Cattails can be partially submerged or in boggy areas with no permanently standing water. Cattails spread rapidly because their seeds blow in the wind and float on the water’s surface and vegetatively they spread from underground rhizomes.

Maidencane (Panicum hemitomon)

Maidencane: Maidencane is part of a family of perennial grasses that are common but somewhat hard to tell apart. Maidencane can grow up to 8 feet tall and often forms dense colonies. It has long, narrowly tapered leaves(up to 12 inches long and 1 inch wide) with rough upper surfaces and margins. Flowers are on a long narrow spike (up to 12 inches long). Maidencane forms extensive rhizomes by which it spreads rapidly.

Pickerelweed (Pontederia cordata)

Pickerelweed: Pickerelweed is a perennial plant that can grow up to 3 1/2 feet tall. Leaves are shiny green, heart-to-lance shaped(up to 7 inches long) singly attached to a long petiole which grow in a rosette from the roots. Each stem can produce a terminal flower spike 3 to 4 inches long. The numerous tubular flowers on the spike are violet-blue in color. Each flower lasts only one day. Pickerelweed reproduces from seeds and rhizomes.

Red Ludwigia (Ludwigia repens)

Red Ludwigia: A classic aquarium plant, grows along the margins of freshwater bodies of water (ditches, rivers, lakes, and ponds). A very polymorphic species in that it readily crosses over with other species of its genus. Similar to Water Primrose.

Smartweed or Water Pepper (Plygonum hydropiperoides)

Smartweed: Smartweed (or Water Pepper) is a perennial plant that forms dense colonies in shallow water or moist soils and can grow to 3 feet tall. Stems are jointed or have swollen leaf nodes that are surrounded by a tubular sheath. Roots can develop from the leaf nodes. Leaves are alternate, lance-shaped up to 4 inches long but usually less than 1/2 inch wide. Flowers are on spikes at the end of stems (often numerous spikes on the same plant). Flowers begin as greenish then turn whitish or light pink in color as they mature. Fruits are flat, triangular (1/8 inch), dark brown to black.

Water Pennywort (Hydrocotyle spp.)

Water Pennywort: Water pennywort is a relatively small perennial plant that seldom exceeds 10 inches in height. Leaf petioles arise from creeping stems and attach to the center of the leaf. Leaves are round with bluntly rounded toothed margins, up to 2 1/2 inches in diameter. Flowers are borne on separate stalks as tall or taller than the leaves. Flowers are white to greenish-white somewhat inconspicuous with tiny simple flowers that arise from a single point on the stalk Pennywort can spread across moist soil or form floating mats on the water’s surface. These mats can break off and form floating islands.

Water Primrose (Ludwigia spp.)

Water Primrose: Water primrose is a perennial plant that stands erect along the shoreline but also forms long runners (up to 16 feet) that creep across wet soil or float out across the water surface. These runners form roots at their nodes. Leaves range from lance-shaped or willow-like (2 to inches long by 1/2 to 1 inch wide) on the erect stems to round or oval 91 to 2 inches in diameter on the floating stems. Leaves can be green to reddish depending on the species. The single flowers are yellow with 4 or 5 petals depending on the species. Flowers vary in size from 1 inch to 2 inches in diameter.