Aquatic Weed Control: Tips For Controlling Weeds In Water Gardens

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By Jackie Carroll

Some of the most lovely and interesting plants for pools and ponds become weeds when conditions are favorable for their rampant growth. Once established, these plants are very difficult to control. This article will tell you more about controlling weeds in water gardens.

What are Water Garden Weeds?

Whether or not a water garden plant is a weed depends on where it is growing. In some cases, harsh winters help keep weeds in check. In warm areas, many common water garden plants become weeds. For example, these are all considered noxious weeds:

Some of them present such an extreme danger to the environment that they are forbidden in some states.

You may think that a plant that reproduces quickly to fill your garden pond with flowers and foliage is just what you’re looking for, but you’ll soon find out why you want to avoid them. The constant battle to keep them under control is more than most gardeners want to deal with, and you risk damaging the environment if they escape into waterways, lakes and streams.

Water garden weeds can clog waterways, make passage by boat impossible, and endanger fish and other wildlife by depriving them of sunlight and oxygen.

Controlling Weeds in Water Gardens

Here are some aquatic weed control methods suitable for garden ponds:

  • The mechanical removal of weeds that like water is the most work, but also the most environmentally friendly. It leaves no chemical residue or decaying plants that can encourage algae blooms. Use a net to remove floating weeds and rake the bottom of the pond to remove weeds rooted in the soil.
  • Woven or plastic barriers prevent the growth of weeds that root in the bottom of the pond by blocking out sunlight. They are expensive to use but very effective. Barriers don’t prevent floating weeds.
  • There are a number of herbicides approved for use in garden ponds. Identify an herbicide that lists the plant on the label. Buy an herbicide labeled for use in ponds, and never use more than the recommended amount.
  • Grass carp are artificially produced fish that are incapable of reproduction, so they can’t overpopulate an area. They consume at least their weight in vegetation every day. Common carp control filamentous algae by feeding on them at the bottom of the pond. One problem with common carp is that they keep the pond muddy because of their feeding habits.

Find out more about invasive water garden plants in your area by contacting your local Cooperative Extension Agent.

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