Chemical / herbicides can be harmful to fish, swimmers, and other pond users if they are used improperly. In many cases, aquatic herbicides contain restrictions regarding swimming, fishing, and watering livestock. They can be much more expensive than the other control options.
Timing is everything if you decide to mow or cut your cattails. Cutting them in May stimulates growth, so wait until late summer if you are only going to cut once. If you cut the cattails below the water line two or three times in a season, very few cattails will grow back the following year. Your cutting will have deprived the roots of their important food source and reduced the amount for storage. Winter cutting will have very little effect on the food in the roots of the plant.
You should cut or mow your cattails with a gas-powered weed trimmer, or another safe, sharp cutting tool. Do not use electrical tools near ponds. Cut the cattails as close to, or under, the water line, removing as much of the leaf blade as possible. Rake or pile the leaves away from the pond or add them to your compost pile. Cattail leaves make excellent, durable canes for chairs, mats, and other home crafts.
Many ponds are built with water control devices. These are useful mechanisms when controlling cattails and other pond plants. To control cattails, reduce the water level during the growing season for mowing or cutting. Alternatively, you can partially freeze the roots if the water level is drawn down in the fall and left low during the coldest weather. Dropping the water level too low may result in oxygen depletion for over wintering fish. Some ponds may refill slowly in spring depending on weather conditions. Avoid dropping the water level late in the fall as many pond animals will have already buried themselves in the mud for the winter and could die of exposure.
In some ponds, the water level can be raised above cattail growth, making it difficult for the plants to obtain oxygen. Flooding must be carefully controlled to keep pond dikes stable.
The methods of cattail control noted above can be combined for more effective treatment. For example, regular mowing and cutting, combined with freezing, can eliminate cattails almost completely. Pond owners should plan their cattail control in advance, taking into account seasonal with freezing, can eliminate cattails almost completely. Pond owners should plan their cattail control in advance, taking into account seasonal weather, wildlife uses, and disposal of cut or dredged material.