Identifying Aquatic Weeds & Algae


Algae grow in various forms. Filamentous algae are most common, growing in strings or mats – often on the surface. Planktonic algae cause green water. It has millions of individual cells that cloud together. Chara is a weed-like form of algae. It grows like a carpet along the bottom of the pond. It has a musky odor and feels gritty. Use Cutrine liquid on filamentous and planktonic & Cutrine granular on chara.

Cattails and Other Emergent Plants

Emergent plants grow around the perimeter of a pond in shallow water with all or most of their foliage above water. Cattails, Bulrush, Reeds, Purple Loose Strife, Pennywart and Pickeralwood are common emergents. Use Shore Clear for best control.


The pondweed family has over a hundred species worldwide with approximately 35 common to North America. The four shown here are the most common. Each of these plants can grow in deeper water – up to 10′ deep in clear water. Sonar, Aquathol Super K and Hydrothol work well to control growth.


This plant grows in thick clumps and is usually not a big problem. The leaves are in whorls of three around the stem. It also grows in deeper water like the pondweeds above. Komeen or Reward are most commonly used to combat Elodea.

Duckweed & Watermeal

Duckweed is hard to control. It forms a thin layer over the surface in calm, wind free ponds. Duckweed will not grow well in moving water so use of a surface aerator will help in controlling growth. For chemical treatment Sonar is the best choice. Often times one Sonar treatment will last for multiple seasons. Reward or Weedtrine mixed with Cutrine and a surfactant can also be used but regrowth can occur quickly if application is not done properly.


While beautiful to look at, waterlilies can become a problem in many ponds. They grow off of a large central root system (much like popal trees). Some growth is great for shade and cover for fish but when left unchecked they will over populate. Use Navigate to control unwanted growth. Shore Clear/Aquastar with surfactant will also work if used after blossoms appear.

Eurasian Milfoil

A very prolific plant! Spreads easily since fragments of plant can re-root and grow. Do not try to remove by raking. Grows very dense making swimming and boating difficult. Sonar or Navigate are best for treatment options.

Other Less Common Weeds: