Which Aquatic Weed Do I Have? And Treatment Options
Alligator Weed
Treatment suggestions for Alligator Weed
Alligator weed is generally distinguished from other plants by its combination of small white papery flowers on short stalks, leaves in opposite pairs and hollow stems. The plant is perennial and generally appears in Australia from November to March. Alligator Weed has an extensive underground root system. Roots are relatively fine and short in water but become thicker in soil, able to grow more than 1m below the surface. The plant forms dense mats of interwoven creeping and layering stems.
Anchored Water Hyacinth
Treatment suggestions for Anchored Water Hyacinth
Anchored Water Hyacinth is closely related to one of the world’s worst aquatic weeds, water hyacinth. The plant leaves are glossy, round and around 5–16cm long and 2–16cm wide. Th stems are smooth and branched. The flowering stems are generally 8–12cm above water. The flowers on the Anchored Water Hyacinth are attractive, funnel-shaped, purple, with 6 toothed petals 1–3cm long. The plant flowers in Summer and Autumn. The plant is known to smother the surface of creeks, lakes and other water bodies.
Arrowhead
Treatment suggestions for Arrowhead
Arrowhead is an emergent aquatic weed with arrowhead-shaped leaves and fleshy, edible tubers. Arrowhead leaves are immersed. The petiole is triangular, erect and can reach lengths anywhere from 5 to 50cm. The leaf blade measures up to 30cm long and 15cm wide. The flowers are white and have rounded petals that appear in whorls of three. The plant blooms mid to late summer.
Azolla
Treatment suggestions for Azolla
Azolla, also referred to as mosquito fern, duckweed fern, fairy moss, or water fern, is a small free-floating fern usually found covering the surface of still or slowly moving waterbodies. Azolla floats on the surface of water by means of numerous small, closely overlapping scale-like leaves, with their roots hanging in the water. Tiny, round, spore-containing structures are sometimes produced at the bases of the side branches. These sporocarps can be green or brown in colour and are usually partially obscured by the ‘leaves’. The plant is highly productive—able to double its biomass in 1.9 days—making it highly invasive.
Marsilea (Common Nardoo)
Treatment suggestions for Marsilea (Common Nardoo)
Marsilea, often referred to as Common Nardoo, is an emergent aquatic fern that grows in wet soils and still to slow moving water. The plant has a long, creeping rootstock and fronds that resemble aquatic four-leaf clovers. The plants often form mats of rhizomes on the surface of the water. The leaflets are bright green and are often hairy when young and sometimes woody when older.
Blue Water Lily
Treatment suggestions for Blue Water Lily
Blue Water Lily, also referred to as cape blue waterlily, or blue Egyptian lotus, is a perennial free-floating plant with a tuberous rhizome. One plant can spread over an area of about 1m. The leaves have long petioles and are polymorphic, changing in form and texture depending on if they are underwater or floating. Blue Water Lily flowers from spring to summer. The flowers can be blue, white, mauve or pinkish in colour, but most commonly have pale bluish-white to sky-blue or mauve petals, smoothly changing to a pale yellow in the centre of the flower.
Blunt Pondweed
Treatment suggestions for Blunt Pondweed
Blunt Pondweed is a perennial submerged aquatic plant with flattened branches, spreading from branching roots. The plant has stalkless translucent narrow leaves with five main longitudinal veins and a rounded tip. Blunt Pondweed can live in stagnant to slow moving water up to 5m deep and can even tolerate mildly saline water.
Cumbungi
Treatment suggestions for Cumbungi
Cumbungi, also referred to as Bulrush or Cat tail, is a tall, rigid emergent weed with flat and strap-like leaves from 1 to 2m long. The plant flowers from spring to summer. The flowering stem is tipped with a cylindrical, brown fluffy spike of densely packed flowers. Fruit is a capsule that breaks off with the stigma and a short hairy flower stalk. Each mature spike can shed up to 222,000 seeds. This is what makes Cumbungi one of Australia’s most invasive aquatic weeds.
Cabomba
Treatment suggestions for Cabomba
Cabomba, or fanwort, is fully a submerged aquatic weed with multiple stems up to 10m long. The plant is an aggressive perennial that forms dense canopies below the water surface. The submerged leaves and stems have a thin gelatinous coating. There are 5 species of cabomba but only one is known to be naturilised in Australia: cabomba caroliniana.
Cape Pond Lily
Treatment suggestions for Cape Pond Lily
Cape Pond Lily, also referred to as Aponogeton distachyos, is a floating aquatic weed with roots attached to the floor. The plant grows in water up to 1.2m deep and produce a floating mat of mottled green and red leaves. The plant can flower all year round. When flowering, white, pinkish or blueish, vanilla-scented flowers protrude above the water surface.
Duckweed
Treatment suggestions for Duckweed
Duckweed is the smallest known flowering plant. The aquatic plants are light green and float on the surface of still moving water, forming large mats that grow quickly. Individual plants within the mat consist of a single, flat, oval-shaped leaf no more than 5mm long. Duckweeds grow mostly by division which is why they grow so fast. As more leaves grow, the plants divide and become separate individuals.
Common Rush
Treatment suggestions for Common Rush
Common Rush is a grassy, flowering perennial plant that grows at the water’s edge in large clumps about 1.5m tall. The plant is commonly found growing in humus-rich areas like marshes. The stems on Common Rush are smooth cylinders with light pith filling with a yellowish inflorescence appearing on one side of the stem about 20cm from the top.
Dirty Dora
Treatment suggestions for Dirty Dora
Dirty Dora is a grassy, hairless, tufted annual that grows up to 750mm high with globular clusters of seeds on short stalks. The plants have long single leaves switching to two short leaves at the top of a triangular stem. Dirty Dora is straw coloured to brown on the lower leaves. The plant stems are green, soft and easily compressed, smooth, triangular and erect.
East India Hygrophilia
Treatment suggestions for East India Hygrophilia
East India Hygrophilia grows underwater with stems emerging above the water surface. Underwater stems may grow up to 2m long, while emergent stems are usually less than 30cm tall. The leaves are pale green or reddish in colour when submerged and bright green on emergent stems. The tiny stalkless flowers are white, bluish or purplish and surrounded by two small hairy bracts.
Leafy Elodea
Treatment suggestions for Leafy Elodea
Leafy Elodea is a submerged aquatic plant that grows in water up to 7m deep. The plant has cylindrical stems that grow up to 1.5m long, sometimes up to 5m. Stems take root at the lower nodes but float for most of their length. The leaves are oval- to oblong-shaped and found in groups/whorls of 4–5. White flowers are found at the water surface on stems up to 8cm long. The flowers have three large petals centred by a cluster of generally nine yellow anthers.
Eurasian Watermilfoil
Treatment suggestions for Eurasian Watermilfoil
Eurasian Watermilfoil is a submerged aquatic plant with long stems that form surface-reaching mats. Leaves are dissected and feathery and in clusters/whorls of four containing 12–21 leaflets. The flowers emerge from the water and are orange to red.
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Floating Pondweed
Treatment suggestions for Floating Pondweed
Floating Pondweed, commonly known as broad-leaved pondweed, is long creeping aquatic plant with rhizome stems that grow up to 4m long. Large leaves grow below the surface and float on top. Submerged leaves are thin and translucent. Floating leaves are thicker and up to 10cm long. Flowers are brownish and appear as dense spikes up to 5cm long. Flowering occurs between September and April.
Giant Sedge
Treatment suggestions for Giant Sedge
Giant Sedge is a grassy perennial plant that grows in shallow waters near the shores of waterbodies. The plant stems are green to red-brown and grow up to 2m long. The flowers are long red-brown spears that start erect before becoming pendulous. The plants flower in late spring to early summer.
Horsetail
Treatment suggestions for Horsetail
Horsetail is a non-wooded, non-flowering perennial plant that grows near the shores of waterbodies and can be highly invasive. Depending on the species, heights vary from 5cm to 120cm. There are two types of stems: pale-brown, unbranched stems that produce fruiting cones and green, branched, hollow stems that do not produce fruit. The stems of common horsetail usually die back to the rhizomes each year, but in other species the above ground growth may survive over winter. Stems break easily at the joints and feel hard and rough due to their silica content.
Hydrocotyl
Treatment suggestions for Hydrocotyl
Hydrocotyl, also known as Pennywort, is a fast-growing aquatic weed that forms a dense mat on the surface of still or slow-flowing freshwater. When floating, the plant forms a tangled mass of roots and leaf stems that can be submerged up to 50cm into the water. The leaves are green, circular or kidney shaped and up to 18cm long. They are either floating or growing up to 40cm above the water’s surface or muddy bank. The flowers are often hidden below the leaf canopy. They are greenish, yellowish or white with five petals 2 to 3mm in diameter.
Hygrophila
Treatment suggestions for Hygrophila
Hygrophila is an aggressive emerging plant that grows on dam shores and in shallow freshwater wetlands. The plants are erect and grow to about 1m tall. Leaves are oblong to elliptic, coarse in texture and have prominent veins and a distinct midrib. The flowers are white, papery and around 10cm long. They are produced in clusters where the leaf joins the stem.
Jointed Twig-Rush
Treatment suggestions for Jointed Twig-Rush
Jointed Twig-Rush is a tall, clumping reed that grows in standing freshwater. The stems are deep green, stiff and cylindrical shaped, and grow up to 2.5m long. The plants typically flower in Summer when rusty-brown, drooping seed heads appear.
Kidney Leaf
Treatment suggestions for Kidney Leaf
Kidney Leaf is a sprawling aquatic weed with kidney-shaped leaves. It can form dense mats on the shore or surface of freshwater. The leaves are bright green, glossy and spongy, and grow up to 5cm wide. The plant typically flowers in summer and autumn when white, mauve to pale blue flowers with six petals appear. The flowers tend to open in the morning and wilt by early afternoon.
Lagarosiphon
Treatment suggestions for Lagarosiphon
Lagarosiphon is a submersed aquatic plant with branched, brittle stems up to 5m long. The stems can form surface-reaching mats of up to 4m from the waterbody floor. The leaves are stiff, curled backwards and arranged in spiral form.
Yellow Burrhead
Treatment suggestions for Yellow Burrhead
Yellow Burrhead is an emergent aquatic plant that grows up 120cm tall. The plants leaves arise from the base of the plant on long three-angled stalks. The leaves are large, fleshy and hairless and contain a milky sap. Flowering can occur throughout the year. Each flower has three large pale-yellow petals, three overlapping green sepals and a cluster of bright yellow stamens at its centre.
Liverwort
Treatment suggestions for Liverwort
Liverwort is a flowerless, spore-producing plant that comes in two main forms—Thallose Liverworts are branching and ribbon-like with flattish, green sheets and grow mostly on moist soil or damp rocks, while Leafy Liverworts consist of leaves on stems and are found in similar habitats as well as on tree trunks.
Primrose Willow
Treatment suggestions for Primrose Willow
Primrose Willow is an upright shrub that grows up to 2m tall. The plant has green to red-brown, hairless, square-shaped stems that are often winged. The leaves are green, elongated and glossy, and hairless or almost hairless. Primrose Willows can flower all year round. The flowers are bright yellow and have four greenish or reddish sepals and four (rarely five) bright yellow petals. The fruits of the plant are sharply four-angled and contain large numbers of tiny dust-like seeds.
Olive Hymenachne
Treatment suggestions for Olive Hymenachne
Olive Hymenachne is a robust perennial grass that grows up to 2.5m tall. The plant can grow above or below water with its roots in the ground. It produces runner stems that run along the ground. The stems can float on water but are not hollow, they contain white pith which makes them buoyant. Leaves are heart-shaped at the base where they clasp around the stem and can get up to 45cm long. They may be covered with long hairs; the upper part of the leaf is narrower and without hairs. The flowers appear as cylindrical clusters at the end of a spike.
Para Grass
Treatment suggestions for Para Grass
Para Grass is an aggressive perennial grass that grows up to 1m tall. The plants stems are hollow, robust and erect towards the ends. The leaf blades are dark green, hairy and less than 1cm wide, they grow up to 15cm long and taper to a fine point. The flower heads are up to 18cm long, made up of several spikes each about 5cm. The seeds cluster thickly along each spike.
Parrot’s Feather
Treatment suggestions for Parrot’s Feather
Parrot’s Feather is a semi-submerged aquatic plant with whorls of feather-like leaves, some submerged and some emerging above the water. Submerged leaves are green and up to 4cm long, while the emergent leaves are slightly smaller with a blue-green appearance. The plant’s stems are spreading, erect and hairless. The flowers are inconspicuous, occurring at the junction between the stem and the leaves on emergent stems.
Peruvian Primrose
Treatment suggestions for Peruvian Primrose
Peruvian Primrose, also referred to as Ludwigia, Water Primrose, Primrose Willow is a large wetland shrub that grows up to 4m tall. The leaves are green with prominent veins and arranged alternately, they grow up to 12cm long. The plant’s younger leaves and stems are hairy. The flowers are bright yellow and up to 4cm across. They appear singly and have four or five petals. The plant’s fruits are reddish or brownish, four-angled and hairy.
Common Reed
Treatment suggestions for Common Reed
Common Reed, also called Phragmite, is a semi-aquatic perennial grass with an extensive rhizome system that can grow up to 4m tall. The thick, leafy, erect stems grow up to 3m high and 2cm wide. The leaves are smooth and flat or loosely in-rolled, growing up to 80cm long and 4cm wide. The flower-heads are large ovoid, dense panicles from up to 40cm long. A tuft of fine silky hairs appears in each spikelet at the base of the upper flowers.
Pondweed (Potamogeton)
Treatment suggestions for Pondweed
Pondweed (Potamogeton) is a hardy aquatic species of plant containing around 160 sub-species. The plants are perennial and grow beneath the water where they form dense, interwoven stem-networks. Pondweed plants can have two different types of leaves; translucent forms that reside underwater and stiffer, more rounded floating leaves.
Red Watermilfoil
Treatment suggestions for Red Watermilfoil
Red Watermilfoil is a perennial aquatic herb with smooth, hairless stems up to 1.5m long. The submerged leaves are disc-shaped and appear in whorls of 3 or 4, growing up to 12mm long. Emergent leaves are a narrow oval-shape, tapering to a point at each end. They are green to reddish-purple and appear in whorls of 3 or 4 (rarely 5), growing up to 9mm long. Small yellowish flowers, up to 4mm long, can appear throughout the year.
Ribbonweed
Treatment suggestions for Ribbonweed
Ribbonweed, also referred to as Eel Grass, is a submerged aquatic grass that grows in fresh water up to 4m deep. The plant has long, green, strap-like leaves.
Salvinia
Treatment suggestions for Salvinia
Salvinia is a free-floating aquatic fern with small green leaves positioned in pairs. Leaf surfaces are covered with long, water-repellent hairs, joined at the tip to form eggbeater shapes. Young leaves are oval shaped, about 12mm across and lie flat on water, often resembling duckweed. As the plant matures, the leaves become thick and fold at the mid-rib.
Senegal Tea
Treatment suggestions for Senegal Tea
Senegal Tea is an emergent aquatic plant that grows on the surface of water, producing runners and floating stems up to 2.5m long. On land, the plant appears as a rounded bush. Leaves grow up to 20cm long and are dark green, shiny and positioned in opposite pairs. The stems are hollow, allowing the plant to float. Young stems are light green with dark green blotches, they start round and become six-sided as plant matures. Flowers are small, white and pompom-shaped, growing up to 2cm in diameter.
Torpedo Grass
Treatment suggestions for Torpedo Grass
Torpedo Grass, also referred to as Bullet Grass, is an emergent semi-aquatic plant growing up to 1m tall. The plant has long, creeping, rhizomatous underground stems with torpedo-like tips. The leaves are flat or rolled with a white waxy covering and grow up to 26cm long. Leaf sheaths can be hairless or hairy. Flowers can appear nearly year-round. When mature and fertile, the florets are yellow or straw-coloured.
Water Chestnut
Treatment suggestions for Water Chestnut
Water Chestnut, also referred to as Water Caltrop, is a free-floating aquatic plant that forms dense mats on the surface of waterways.Leaves are either submerged or floating. Submerged leaves are feather-like and arranged in whorls around the stem. Floating leaves appear in circular clusters with leaves radiating out. They are glossy on top and oval, triangular or diamond-shaped with a saw-toothed edge, and grow up to 3cm long. Flowering occurs in early summer. The flowers appear above the water’s surface and are white with four petals up to 8mm long.
Water Hyacinth
Treatment suggestions for Water Hyacinth
Water Hyacinth is one of the world’s most invasive free-floating aquatic weeds. The plant grows up to 65cm tall and has an extensive feathery, black to purple root system that can go down to 1m deep. Leaves are bright to dark green, sometimes rusty yellow on their edges. They are glossy, smooth and hairless, and grow up to 10cm in diameter. Leaf stalks of young plants are swollen into spongy, bulbous structures, while mature plants have elongated leaf stalks. Flowers appear as dense spikes above plant. They are light purple with a darker blue/purple and yellow centre and grow up to 6cm long.
Water Lettuce
Treatment suggestions for Water Lettuce
Water Lettuce, also called Water Cabbage or Nile Cabbage, is a spongey, free-floating aquatic plant resembling a small, open head of lettuce. Leaves are green, fan-shaped and covered with hairs. The roots are tufted, feathery and up to 80cm long. Flowers are small, green and grow up to 2cm long.
Water Snowflake
Treatment suggestions for Water Snowflake
Water Snowflake is a free-floating aquatic plant that spreads by rhizomes and forms clusters of flat, emerald-green leaves that float on the surface of the water, resembling water lilies. Leaves can grow up to 50cm in diameter. Flowers are small, about 1cm across, and are usually snow white in colour with orange/yellow in the centre. They are arranged in clusters, commonly with 5 petals in a star shape.
Water Soldier
Treatment suggestions for Water Soldier
Water soldier is a most-often submerged aquatic plant that grows in water up to 5m deep. For most of the year, the plant grows underwater, but in spring new leaves containing air pockets form causing the plant to float. Leaves above the water are dark green, fleshy and serrated with spines along the margins. Submerged leaves are lighter green or reddish-purple. In summer, the plant flowers above the water. The flowers are white with 3 roundish petals and smell foul. As older leaves die back in autumn, they become waterlogged causing the plant to sink again.
Sea Tassel
Treatment suggestions for Sea Tassel
Sea Tassel is a long, thin grass-like aquatic weed found in stationary freshwater or saltwater bodies like estuaries. The branches emerge from the sediment of the waterbody. They are narrow and have a zigzag branching pattern. The branches can grow up to 2.5m long, while the leaves, which are dark green and arranged along the branches, grow up to 25cm long. During summer, the plant often produces yellowish-green flowers, 3-5mm in size.
Brown Beetle Grass
Treatment suggestions for Brown Beetle Grass
Brown Beetle Grass is a narrow, erect perennial or biennial grass that grows to 150cm high and forms well-rooted tussocks. The leaves are smooth and hairless and rolled longitudinally upon themselves when dry. Leaf-blades are 15-30 cm long and 1-2 mm wide when flattened out.
Water Couch
Treatment suggestions for Water Couch
Water Couch is semi-aquatic, perennial grass with long rhizomes and stolons (ground runners). The plant stems stand erect and can reach 60cm tall. The stem nodes are often hairy. The leaves are sharp-pointed, flat blades that grow up to 20cm long and 7mm wide. The leaves are hairless but tiny, dense hairlike structures may be found along margins of the blades and sheaths.
