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I think I have grass growing in my pond. Could it be Sago pondweed? | Ponds & Lakes Q&A


Q: I think I have grass growing in my pond. Could it be Sago pondweed?

Q: I think I have grass growing in my pond. Could it be Sago pondweed?

Lewie- Gwinner, ND

A: Sago pondweed, or Potamogeton pectinatus, is a distinctive aquatic plant that kind of does resemble grass.

Sago is a perennial that grows from thickly matted rhizomes. It has no floating leaves, but it has thin, long and branching stems with tapering, filament-like leaves that are 1/16 of an inch wide and 2 to 12 inches in length. The leaves grow in thick layers and originate from a sheath. The plants produce a nut-like fruit that’s 1/8 to 1/4 inch long and 1/10 to 1/8 inch wide.

Pondweed Pros and Cons
The Sago pondweed, like other aquatic plants, provides habitat for many below- and above-the-surface critters. From the birds that eat the plant’s fruit and tubers to the fish that find food and safety in their stems, the pondweed has lots of fans. Even fungi and beneficial bacteria benefit from it – as the plant decomposes, the microorganisms feed on the detritus.

But Sago also has its drawbacks. Plants rapidly spread between bodies of water. In a small water body or backyard pond, unchecked Sago can become a nuisance. And when you do mechanically remove it, remaining plant fragments, including leaves and roots, can sprout new growth.

Controlling Sago
If you suspect Sago in your pond, you have several management options. Here’s what we recommend to help you get the weed under control.

  1. Herbicides: To rid your pond or lake of Sago, an herbicide will be necessary.
    • Sonar™ A.S. is a season-long herbicide. One treatment wipes out Sago and many other common floating and submerged pond weeds for the entire season.
    • Ultra PondWeed Defense® is a broad-spectrum herbicide that will quickly kill Sago. It doesn’t stay in the water body, however, so multiple treatments may be necessary.
    • Clipper™ is a fast and selective herbicide that controls tough invasive and nuisance floating and submerged aquatic plants. It comes in a fine wettable powder to spray weeds.
  2. Mechanical Removal: Once it has turned brown and died, Sago pondweed can be removed by raking it with a Weed Raker™ – but remember that the plant will sprout and reestablish from any remaining roots, seeds and foliage fragments.
  3. Pond Dye: Non-toxic dyes, like Pond Logic® Pond Dye, reduce and prevent Sago pondweed growth by limiting sunlight penetration.
  4. Aeration and Beneficial Bacteria: Aerating your pond or lake with an Airmax® Aeration System can help, too – particularly if you’re using the beneficial bacteria found in PondClear™ . The extra oxygen in the water fuels the tiny bacteria as they break down nutrients that fertilize the Sago.

Pond Talk: Have you ever had Sago pondweed in your pond or lake? How did you get it under control?

Broad Spectrum Control - Pond Logic(r) Ultra PondWeed Defense (r)

6 Responses

  1. to Ranger Bill: I like that idea — and that’s basically what I have been doing –ripping it out. Actually, I never even gave the “grass” that grows in my pond (a half acre and 9 to 11 feet deep) much thought or even knew it had a name. It “tickles” my legs only at the very lowest depths (it’s a banked pond) and doesn’t bother me at all. I feel the less I hassle with nature, the happier nature will be. It does what it needs to do. Maybe that’s oversimplification . . .

  2. does the Sonar herbicide kill water lilies and other aquatic plants? So many pond cleaners are guilty of that and I am reluctant to use them. The only thing that seems safe is a product I use that colors the water a gorgeous dark blue and filters out the sunlight to prevent algae growth

    • Hi Silvia – Sonar is an aquatic herbicide. When used in the spring (with little outflow), it will kill and prevent many submerged pondweed growth. Sonar is not effective at killing or preventing water lily growth.

      • Mel, thank you! One issue I have is that I am at my country house (where the pond is) starting only mid-June so I’m not up here to do anything in the spring. Does it really matter if I were to apply the Sonar in mid to late-June?

      • We suggest the spring so that it’s in the pond prior to when weeds begin to grow. By June, some weeds will already be established, so it will take longer for you to see results. Perennial pondweed growth is similar to perennials on land. Certain pondweeds are found are certain times of the year. So, while you may miss the early pondweeds, you will still protect against the weeds that show up later in the summer.

  3. I think Sago Pondweed is beneficial and I just rip some out if it gets too big.

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