Q: What is this horrible clover-like weed I am seeing everywhere, including my lawn. The flower is a round, yellow cluster. It runs similar to crabgrass but I think the leaves look like clover. My wife says it is not clover, but I think it is. We have a bet on this; the loser has to clean the kitchen for a week. So you get to decide – what is it?
A: I always hate to get into the middle of a husband and wife disagreement especially when cleaning the kitchen is the bet. So, I will have to agree with you that the leaves are similar to clover but your wife is correct in that it is not clover. The weed you brought to the office is Black medic, Medicago lupulina. The name sounds ominous does it not?
This plant originated from the Mediterranean. It has traditionally been used as a winter annual crop cover in the United States for corn, soybeans and small grains. The best time to get rid of the weed is as the black seed clusters are maturing. It is fairly easy to pull which is the best method of control, since it is an annual, and reproduces only by seed. Once the plant and seeds are removed then next years crop will be greatly diminished.
Any chemical weed killer will be of little benefit as these are currently fully grown adult plants. The time to apply a chemical is when the weed is very small and before it has reached reproductive stages. This weed grows in the same type of environment as clover and they are often seen together. One other important fact, black medic can be an indication the lawn has too little nitrogen.