Clover and black medic can be considered either desirable plants or weeds, depending on who is telling the story. As desirable plants, they add nitrogen to the soil, mine minerals from the subsoil and reduce compaction because of the deep root systems. The flowers and foliage are considered attractive by many people. Some lawn seed mixes deliberately include clover. Other people consider the these plants weeds because they are of a different texture than the grasses.
If you are among those who consider them a weed and would like to remove them, try a premix such as Trimec that contains dicamba, MCPP, and 2,4-D can be effective. Folks often try 2,4-D with poor results; many clover and black medic populations are resistant to this herbicide. Surface portions of the plants are damaged, but they quickly recover and density can increase. Another good option for control is to carefully apply glyphosate (e.g. Roundup), because this herbicide will move into the root system. Glyphosate is relatively safe for humans and the environment and it breaks down rapidly. Remember that even though glyphosate is relatively benign in the environment, it will kill any plant it touches, including grasses and trees, so apply it very carefully. One method of application is to wear rubber gloves and apply it with a sponge or with a cloth glove worn over the rubber glove and dipped directly into the solution. If glyphosate is used, select the concentrate formulation rather than the ready-to-use products, which are often less effective. Mix the concentrate according to label directions. Herbicides containing triclopyr can also be useful. When using any pesticide, be sure to read all label instructions and follow them carefully. Wear necessary protective clothing and equipment.
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Written by Sherry Lajeunesse, Extension Urban Pest Management Specialist. Sept., 1997