Aquatic Weed Identification Guide

Identification White Water Lily: Large white flowers (sometimes pink-tinged) on stalks just above the water. Rounded, leathery leaves up to 30 cm across float on the surface. Yellow Water Lily: Smaller, cup-shaped yellow flowers with more oval and smaller leaves. Description Widespread across UK waters, growing in depths up to 5m. Flowers from June to August. While lilies are often visually appealing and beneficial, excessive growth can blanket the surface, restricting light and other plants' growth. Periodic cutting or rhizome removal may be needed to maintain balance.

Identification Canadian Pond-weed: Freshwater herb with much-branched stems up to 3m long. Leaves are dark green and grow in whorls of three along the middle and terminal parts of the stem, becoming denser toward the ends. Nuttall's Water-weed: Similar appearance but with longer, more slender stems, often freely branched. Leaves are pale green, evenly spaced, typically in whorls of 3 or occasionally 4. Description This highly invasive perennial plant family originates from North America. In UK waters they grow rapidly in shallow areas, outcompeting native species, reducing biodiversity, and clogging waterways. Despite being labelled as "oxygenating plants", dense growth can cause oxygen level fluctuations harmful to fish and invertebrates. Both species are listed under Schedule 9 of the Wildlife and Countryside Act (England & Wales), making it an offence to plant them in the wild. Best management involves cutting in spring to hinder new growth and removing all cut material from the watercourse.

Identification Leaves: Floating, dark green, leathery, 5–10 cm long, pointed tips and rounded bases. Flower: Dull yellow-green on 5–10 cm stalks. Description A fast-growing perennial common in UK lakes, ponds, and canals. Grows in still freshwater, typically in water under 1m deep but can reach 2m. Flowers from May to September.

Identification Appears as a "floating rope" with branched stems and strongly curled leaves that alternate along the stem. Individual stems can reach up to 3m long. Description Native to South Africa, this invasive species thrives in UK waters. Similar in impact to the Elodea family, it rapidly outcompetes native species, causes biodiversity loss, and blocks water flow. Despite its oxygenating reputation, dense infestations can destabilize oxygen levels and harm aquatic life. There have been cases of Curly Waterweed completely filling large lakes in the UK and Ireland. It is listed under Schedule 9 of the Wildlife and Countryside Act, making its planting in the wild illegal.

Identification Tiny floating plants, each 1.5–5 mm in diameter, forming dense yellow-green mats across water surfaces. Description Common in ponds, canals, and flooded gravel pits. Duckweed reproduces by division and can rapidly blanket entire surfaces, blocking light and oxygen exchange. Removal by hand is difficult due to its size. Aquaclear uses Truxor's specialized tools to scoop and remove duckweed effectively from watercourses.

Identification Leaves: Rosettes of sword-shaped, serrated leaves growing from a central point and attached by long, thin strands from the waterbed. Flower: Single, three-petaled white (sometimes pinkish) flower held above water during summer. Description Native to Europe, these plants remain submerged most of the year, surfacing and flowering from June to August. Manageable in small numbers, but large populations can choke small waterways.

Identification Appears as foam, scum, or mats on or below the water surface, usually bright green to yellowish in colour, often resembling a paint spill. Description Algal blooms occur from nutrient overabundance (from runoff), warm temperatures, and still water. These blooms can damage ecosystems by depleting oxygen and blocking light. Harmful Algal Blooms (HABs): Potentially toxic, often indistinguishable from non-toxic blooms, can harm or kill animals. Non-toxic Blooms: Still harmful, causing oxygen loss and disrupting ecosystems when decomposing. Control options include mechanical removal, improving water flow, and using barley straw rafts to limit growth. You can find out more about our work with blanket weed on our Blanket Weed Removal page.