Winter is a good time to freeze out pond weeds

Pond Milfoil

Eradicate rooted pond weeds by freezing the roots

Winter has finally arrived. You’re curled up by your wood stove with a good novel and perhaps a mug of hot chocolate.  You mull it over: holidays are coming; family will soon be here, the joy of the season is settling in. Your pond, which may have iced over already,  is the furthest thing from your mind.

Isn’t that a lovely story? Unfortunately, there is one thing that could be done now before you can settle in for your long winter nap: Pond Weeding. You know what I mean – those pesky, tangled mats of vegetation that take up residence in around your pond each summer. They’re ugly, they’re unpleasant, they tangle fishing lines, they gross out swimmers and they’re embarrassing.  But are they preventable?  Yes.   All you need to do is start now.

There are a couple approaches to this task, and most of them suck. You can wait until they appear again next summer then get out a weed rake and cutter and start hacking at them yourself, if hard labor is how you want to spend a summer afternoon.  You can try sprays, but these are both scary to use and very bad for the environment.  Too little spray and you’ve wasted your money, too much and your fish will be floating belly-up.  Another solution is grass carp, which are effective, but illegal in many states.  So what works?

The answer, as usual, is simpler than one might think: Freezing.

Freezing can work for you if:

•             You live far enough north that ground freezes six to twelve inches deep in the winter


•             You can draw down your pond’s water level and maintain it at that point for 30 days

The basic concept is to freeze the root systems of pesky underwater weeds so they can’t send up new sprouts in the spring.  Small, soft plants such as water milfoil, naiads, water violets, etc. have a shallow root system and can be removed quite easily.  Larger plants, especially those with tubers such as water lilies or particularly resilient cattails will take some more time.

Lowering the water level to freeze the bottom might sound dangerous, but if done correctly it poses no harm to your fish.  Here’s how:

  • Lower the water enough to expose the pond bottom in the zone that grew weeds last year.
  • Leave a pool of water deep enough so that your fish have room to survive without risk of being frozen

The above two goals may result in a compromise between the two for shallow ponds.  If so, always err on the side of protecting your fish.

  • Keep the water level low for one month
  • Aim for the coldest 30 days of the year

§  For the mid-Atlantic, that’s January to February

§  Further south, that’s December to January

§  Further north is a different case; aim for the coldest snow less month.  Snow tends to insulate, slowing the freezing process

Finally, sit back, enjoy your hot cocoa, and think about how glad you are that all your pond weeding is done for next year.