Answer: Ants are terrific soil builders and as a general rule don't harm plants. My friend the entomologist is an "ant expert" and she says there are only a couple species of ants that actually eat plants. The more likely scenario is the ants are interested in the other insects on your plants. In cooler weather, ants "herd" aphids, protecting them from predators in exchange for honeydew, the sweet excrement the aphids produce. It'll be obvious if this is the case in your garden - you'll see ants on plant stems and leaves and clusters of pale green/brown soft-bodied aphids nearby. You can control them by first blasting them off the plants with a strong spray of water. You might need to do this daily, making sure you get underneath and between leaves where the aphids may be lurking.
In warm weather, if you still want to try to get rid of the ant hills, make an orange slurry in a blender with orange rinds and water. Immediately pour it into the ant hill. It gives off fumes the ants can't handle. This works best in warm weather and must be done immediately or it loses its potency. I personally don't do anything to control ants if they aren't damaging plants since they are aerating the soil so industriously!
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