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Keeping your pond weeds under control can be a vexing issue. The first step towards finding the right solution is properly identifying which specific weed is your nuisance plant. Most ponds have different types of plants and you don’t want to start the wrong treatment – some pond plants may be beneficial to local and migratory wildlife, and you may not want to eliminate those kinds.

Though there are many types of aquatic weeds, the good news is that in comparison to pasture and turf grass weeds, pond weeds can be easier to identify.

There are four main types of pond weeds: algae, emergent, floating and submerged.


Some algae, like planktonic algae, are microscopic, while others are large and resemble higher plants, except that they lack true roots – like chara. Algae are a common nuisance with no defined root system. It often floats on the pond’s surface in mats, although it may emerge at the pond’s bottom before floating to the surface.

Filamentous algae, sometimes called moss, can blanket the bottom of your pond while clumps of it can float to the surface. It will often form mats that float on the surface of your pond that resemble wet wool. This kind of algae is commonly referred to as “pond scum” – it’s also known as string algae or floating algae. If left untreated, it can cover the entire surface of your pond. Oscillatoria is a form of filamentous algae that is sometimes referred to as black algae, or blue-green algae. It can also give your pond a red-purple tint.

Chara looks like submerged weed, but can be differentiated by its musky smell. It grows on the bottom of the pond floor in large pillows and is frequently misidentified as a weed. It will not grow above the surface of the water. It features a crunchy texture.

Emergent Plants

Emergent plants are rooted plants that are often along the shoreline – they stand above the surface of the water, like cattails. The stems of emergent plants are somewhat firm or stiff.

Some common emergent weeds are alligator weed, water pennywort, and smartweed. Alligator weed forms very dense strands or mats, making shoreline access difficult. Their stems are hollow, their leaves are the opposite and they include prominent mid-rib. The flowers are white, and small, on long branches that resemble white clover. Water pennywort usually forms dense mats along shorelines, but can also be floating mats or islands. Leaves are dark green and round with blunt indentations rising from the center stem. Tiny white and greenish-white flowers with five petals arise from a single point on the stalk, somewhat resembling a four-leaf clover.

Smartweed can grow up to three feet tall in the shallow water. Stems are jointed, leaves are alternate and up to four inches long. Flowers are green and turn white or light pink as they mature.

Floating Plants

True floating plants are not attached to the bottom. They come in sizes from very small, like duckweed, to over a foot in diameter, like the water hyacinth. Most have roots that hang in the water from the floating green portions. Duckweeds form dense blankets that cover the surface of still water. They range in color from light green to dark green and they have a flattened, leaf-like structure with hanging roots and small leaves.

Submerged Plants

One of the worst submerged weeds is Hydrilla. It grows quickly, with long leaves and sharply serrated edges – its leaves are rough to the touch. Flowers grown from their upper branches are translucent to white in color. Coontail is rootless, and can grow up to fifteen feet tall. It forms dense colonies, with elongated stems, and branches that are rough to the touch. Curly-leaf Pondweed appears reddish-brown in the water, but is actually green when examined out of the water. Its leaves are wavy, stiff and crinkled, with a “crispy” texture. Eurasian milfoil is an exotic invasive submerged perennial. It reproduces in both a vegetative manner, and through seeds. A single piece of Eurasian milfoil can multiply into 250 million new plants in a single year!

Now that you know what you’re looking at, you can identify the right all-natural or chemical solution from Healthy Ponds® to help solve your pond issue.