Managing Wetlands: Controlling Undesirable Species

Undesirable plants are defined as plants that can cause problems in wetlands under certain conditions. These plants in turn can provide beneficial conditions in other circumstances. For example, marsh smartweed, being a perennial, produces very little seed and can crowd out other more beneficial plants, but it provides an excellent environment for invertebrates, another important food source for many wetland wildlife species. In some cases, plants are listed as undesirable because they are very aggressive and will crowd out other plants, resulting in a monotypic stand, which is less desirable than a mixture of plants.

Problem Plants and Their Control

1. Cocklebur: Summer flooding with shallow water when plants are less than 12 inches. Mowing to 4 inches when plant begins to put on seed. Shallow discing any plant height. 2-4D at 1/4-I/2 pound/acre.
2. Willow, cottonwood, maple, green ash: Heavy/deep discing in summer. Double cross discing in growing season. Mowing in fall, followed by flooding next growing season.
3. Marsh mallow, buttonbush: Heavy offset discing in summer, repeated 2-4 weeks. Spraying Rodeo in early growing season at rate 1 pt.-l qt./acre. Weed wipe 50 percent Rodeo.
4. Cattails, river bulrush: Burn twice in summer, flood 3 feet deep from fall through next growing season. Muskrat populations to create openings. Spray Rodeo, 1 qt./ acre.
5. American lotus: Dewater in February or at any point before new leaves reach water surface, optional shallow discing after dewatering. Spray Rodeo, 1 qt./ acre.
6. Marsh smartweed (P. coccirzeum): Heavy deep discing in summer followed by herbicide treatment of regrowth. Apply Rodeo at 1 qt. /acre.
7. Purple loosestrife: Applying Rodeo during full bloom (July-August) in a 1 to 2 percent solution with a surfactant is the only reliable control technique

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