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Controlling Phragmites – Pond & Lake Q & A

Picture of Phragmites.

Pond & Lake Q & A

Q: How do I control invasive Phragmites in my lake?

A: The common reed, Phragmites australis, may seem innocent enough, but these tall grasses topped with feathery tufts can quickly crowd a farm pond or lake. Native and non-invasive varieties of the plants have thrived in wetlands for centuries throughout the United States, but invasive varieties have taken root on the East Coast, Midwest and Pacific Northwest, and in your lake, creating a nuisance along shorelines.

Phragmites Explained
Growing along streams and ponds, phragmites is a perennial wetland grass that can grow to 6 to 15 feet high. The stems, which are erect, smooth and hollow, may be nearly 1 inch in diameter and are topped with 12-inch-long dense panicles, or purple-brown pyramid-shaped plumes of flowers, that emerge between July and September. Leaves arise from the stem are 10 to 20 inches long and up to 2 inches wide.

The plants propagate mainly via an extensive network of underground rhizomes, or horizontal stems, that produce roots and shoots that grow as deep as 39 inches, with their root systems growing down another 3 feet. Dense above ground and below, stands of these plants crowd out native plants and animals; block shorelines, reducing access for swimming, hunting and fishing; and create fire hazards from dry plant material. But they can be controlled.

Controlling the Common Reed
Once phragmites has invaded your lake or pond, you’ll need to develop a long-term management plan to control the plant. Unfortunately, because the plants spread through their rhizomes, they could be difficult to eradicate entirely. That’s where chemical and mechanical control can help.

Herbicidal Control: First, you can spray a herbicide and surfactant product, like Shoreline Defense® & Treatment Booster™ PLUS Combo, in the late summer or early fall. Mix 8 ounces of Shoreline Defense® and 4 ounces of Treatment Booster™ PLUS with 2 gallons of water. Pour into pond sprayer (like the The Pond Guy® Specialty Pond Sprayer) and spray on the plants to completely wet the surface of the leaves. Allow the mixture to absorb into the plant and the root system, the most difficult part of the plant to kill, for one to two weeks.

Mechanical Control: Once the herbicide has had a chance to soak into the phragmites’ root system, you can use a weed cutter to cut at the base of the plants, allowing for easier removal with a pond rake. If you can control your pond’s or lake’s water line, you can also cut the phragmites 2 to 3 inches below the water surface to cut off the plant’s supply of oxygen and drown the plant. To prevent the accidental spread of the plant, collect the cut material and bag it before disposing of it.

Plan to repeat this routine several years in a row. Patches may emerge even after regular treatments, but once you’ve wiped out the majority of the phragmites, the plant will be much easier to control. Good luck!

POND TALK: How do you control phragmites in your pond or lake?

3 Responses

  1. It’s late august and I am on my way out of my pond to wage war on the enemy phragmites. I have read your recommended plan of attack but have some questions.

    My phragmites range in size from about 2 feet to 6 feet tall and go around the way around the edge of my pond, about 2 feet to 3 feet wide. They have totally consumed the entire shoreline of my pad.

    1. I am planning to use a surfactant called Rodeo. Do you have an opinion of its effectiveness?

    2. If the stems are hollow, why wouldn’t you want to cut the plant down to about 12 inches from the ground and then spray the surfactant add to the plant? Wouldn’t that exposed the plants interior and allow the plant to soak up the poison in greater volume?

    Just trying to think outside the box and minimize the number of battles I am going wage on the enemy. I thought maybe you or some of your readers may have tried using this plan and wanted to hear if it helped shortened the war. Any feedback is much appreciated.


    • Hi Michelle – Rodeo is also a product that contains glyphosate just check the concentration against others for a strength comparison. The reason we don’t recommend cutting them down first is because you want the plant to still be green and growing so it will pull the chemical throughout its system and into the massive root system that you cannot see under the surface. Simply soaking the stalk of the plant does not incorporate it into the root system. Good luck!

  2. how do I control Cat Tails in my ponds ?

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