The Big Four Bad Weeds

There are dozens of common lake weeds.

They may or may not be a problem, depending where they’re growing. Most of the native lake weeds mind their own business, but there are several exotic, invasive species that can literally take over a lake quickly.

Here are four of the most aggressive, problematic invasive species.

Wild Celery

The thing about wild celery is, it’s really great for wildlife; ducks and all sorts of critters love to eat wild celery, it helps prevent erosion and as lake weeds go, it’s not a bad looking plant.
On the other hand, wild celery is not so great for your beach front. The problem is, it’s hard to get rid of. Wild celery has rhizomes, (little connector-things that spread under the soil) so even if you pull up the plants or poison them, the rhizomes are almost impossible to control and will send up new plants.

That said, no plant can grow in the absence of sunlight, even tough rhizome plants like wild celery, cattails and lily pads can’t grow without any sunlight.

Placing a LakeMat® (a benthic barrier) over an area of your lake bottom not only blocks sunlight, it also increases the level of volatile fatty acids (VFA) in the soil beneath it. Rhizomes don’t like this type of soil at all.

Here’s a good little explanation about the characteristics of wild celery.
Wild Celery:  DNR State Maryland Gov

Starry Stonewort

“Starry stonewort may be the greatest challenge that has ever faced lake management professionals and lake user groups in Michigan. The impact on Michigan fisheries could be profound.”

Wow, is that scary statement, from the report “A Decade of Starry Stonewart in Michigan,” released by the University of Michigan. Here’s another quote from an aquatic biologist. “Starry stonewart grows to resemble something like a coral reef, it’s like a solid wall,” says Joel Steenstra, of Summit Laboratory in Grand Rapids, MI.

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Like a coral reef? Holy smokes!

Here’s more from the U of M report:

“The biology of starry stonewort is very different in Michigan, where it is a hardy and aggressive opportunist, and Europe, where it is a threatened species. It also seems peculiar that starry stonewort inhabited Lake St. Clair for nearly 30 years before it became conspicuous in inland lakes and then to have spread so rapidly throughout the lower peninsula of Michigan. This suggests that the starry stonewort now found in Michigan lakes is a particular genotype or even a hybrid that is distinct from the starry stonewort found in Europe…”

So, Europe’s starry stonewort is wimpy, and ours is ready to take on all comers! Why? It may have become a hybrid with our own native chara. The result: “Weeds Gone Wild!”

There is an upside to starry stonewort. It quickly chokes out eurasian milfoil and everything else. It also clears up the water like zebra mussels. In fact, zebra mussels seem to like starry stonewort. The thing is, starry stonewort chokes out just about everything and squeezes large fish bedding areas. It is not a good weed to have in your lake…not at all.

Though it responds to chemical treatment, starry stonewort grows so thick, the chemicals only “burn” the weeds on top. Some herbicide applicators refer to this as a “haircut treatment,” meaning they can’t get it all, just the upper portion of the mass of starry stonewort. There’s just too much bio-mass to get rid of starry stonewart completely without killing everything in the lake. And because it creates so much mass so quickly, mechanical harvesters have a difficult time with starry stonewart.

Starry stonewort isn’t a true (vascular) plant; it’s an algae. Vascular plants like coontail, naiad and curly leaf pondweed are far more complex and easier to control. Think of it as regular plants being like General Motors and algae is like a bunch of guys building cars in their garages independently. Each algae cell is its own little factory.

Placing a LakeMat® on the lake bottom will prevent sunlight from reaching starry stonewort, thereby controlling it. Even though starry stonewort has no true root system, (it could theoretically grow in a glass of water) it prefers to anchor itself in soil and will migrate with water movement until it finds a suitable spot…not on a LakeMat®, though it may move across it from time to time like a tumble weed.

Here’s a good link to more information on starry stonewart: Michigan Lake Info

Eurasian Watermilfoil

In northern areas, eurasian watermilfoil has been the king of invasive aquatic weeds for more than a century. It was brought to North America as an ornamental plant for ponds and aquariums and quickly escaped to lakes, becoming a nuisance, invasive plant that crowds out native plants.

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Many shallow lakes have been observed to have large mats of eurasian watermilfoil reaching all the way from one side of the lake to the other by late summer. The weed tends to grow very thick, in tangles masses. It is the primary plant many of us think of when discussing obnoxious lake weeds.

Because eurasian watermilfoil can reproduce by fragmentation, attempts at raking, pulling, or otherwise disturbing the plants creates more weeds as small eurasian watermilfoil fragments break off, sink to the bottom and create more weeds. It’s these small fragments that cling to boats and trailers that help spread eurasian watermilfoil from lake to lake.

Herbicide treatment can be effective, eradicating up to 85 percent of eurasian watermilfoil per season. However, with each application, eurasian watermilfoil becomes more resistant and harder to control with each new season.

A benthic barrier, such as a LakeMat® will prevent eurasian watermilfoil from conducting photosynthesis or taking root on the lake bottom. Masses of uprooted eurasian watermilfoil may float in from time to time, but with nothing to stick to, it will usually drift by any area where there are no existing weeds.

Here’s a good link from the Minnesota Dept. of Natural Resources about  eurasian watermilfoil:  DNR MN Depart. Of Natural Resources


Hydrilla might well be called the Godzilla of lake weeds. In many ways, hydrilla is the most difficult invasive aquatic weed in the United States. Hydrilla can reproduce in several ways, fragmentation, tubers, turions and seeds, it’s certainly tenacious.

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Hydrilla can grow up to one inch per day, with stems reaching up to 30 feet long. To make matters worse, it can grow in low light conditions, out-competing other plants.

There have been several instances of benthic barriers, such as the LakeMat® being used to successfully suppress the growth of hydrilla around boat docks and swimming areas.

In many cases, benthic barriers are used in conjunction with herbicide treatment to control hydrilla. The barriers are used in foot traffic areas and boat docking areas while the herbicides are applied farther out and in boating lanes.

The big trick with hydrilla is to stop it as quickly as possible and stay on top of it.

Here’s a very good piece on hydrilla from Washington State:  State Of Washington Depart. Of Ecology