When the crisp foliage and cigarlike flower heads of cattail plants (Typha spp.) combine in a home pond setting, the effect can be striking. The hardy, freshwater plants add vertical interest and unusual texture, and they attract birds and other wildlife. Given time, however, these vigorous plants get out of hand. Salt block effectively battles cattails but comes with ramifications. Depending on your goals, other elimination methods may be better suited to your needs.
Cattails reproduce through copious seed and robust rhizomes growing in a pond floor. The rhizomes store the plants' energy and fuel their annual growth. Healthy rhizomes can grow as much as 2 feet during a summer, and they form underwater shoots that eventually rise above the water's surface. Those stems become essential pathways that deliver air to the rhizomes. Cattail hardiness depends on the species. Broadleaf cattail (Typha latifolia) is hardy from U.S. Department of Agriculture plant hardiness zone 3 through 11. All cattails have a very low tolerance for salinity.
Controlling Them with Salt
Adding salt blocks to your pond water will slow cattails' growth, prevent the plants' seed germination and eventually kill the cattails at all life stages. The number of salt blocks needed depends on the pond's size. According to the U.S. Department of the Interior's Fish and Wildlife Service, saline rates of 10 parts per trillion are sufficient for cattail control. Seawater, at 30 to 50 parts per trillion, kills cattails within two months. In order for salt applications to be effective, the water needs to stay stagnant, not refreshed. The salinity created will affect all the other freshwater plants and creatures in the pond.
Exercising Mechanical Options
According to the Fish and Wildlife Service, the most effective non-chemical way to eliminate cattails is to cut off their air passage. The passage functions whether stems are green or brown. Cutting cattails several inches below the water's surface stops airflow and prevents the replenishment of energy reserves. The best time to cut stems is in summer, when rhizome reserves bottom out. New shoots won't have enough energy to break above the water. Summer cutting also removes flower heads before they go to seed and eliminates the eyesore of slowly dying, yellow plants that saline creates.
Using Chemical Remedies
Properly applied and timed, aquatic chemicals effectively and safely kill cattails without the side effects of salt. In late summer and fall, cattails store rhizome reserves. Chemicals applied during that time move speedily through the plants. Glyphosate products designed for aquatic use kill the cattail parts it contacts and the rhizomes below. A 0.75-percent solution of one aquatic glyphosate product is made by mixing 2 tablespoons of aquatic glyphosate with 1 gallon of water, but directions differ among products and brands. Wear gloves, other clothing to cover all of your skin and eye-wear, and follow precisely the instructions of the product you use. Spray cattails until they are wet but not to the point the solution runs off them. Results should be visible in about one week.