Here's a weird problem: for the first time in the three years we lived in our 6th floor apartment we have an infestation of little black ants. Worse yet, they seem to have taken over several potted plants and turned them into "ant hills" by colonizing through the bottom of the pots.
Do you have any suggestions about how to clear them out? I will appreciate any guidance you can offer, as I know the Horticultural Society has been able to help us in the past about other matters.
Nice to hear from you. Honestly, that ant situation is a new thing to me. I must admit, though, that I do not know as much about ants as I do other garden pests. This is what I do know:
Ants themselves do not typically do damage to or kill plants. (If they are doing damage to the roots via their tunneling, that might be another story). If ants are present, it is typically because they have found a source of honeydew to feed on. Aphids and other garden pests feed on the leaf tissue and their excrement, technically called frass, is a sweet, sticky substance called honeydew. Large quantities of honeydew on leaves can lead to a dark fungal coating called sooty mold, and can also invite ants to feed.
I would recommend inspecting your plants and seeing if you see any other signs of insects. Be sure to look on the undersides of the leaves and at the nodes, the junctions where stems and leaves meet, as these are safe places for pests to hide and feed. If you find other culprits, (aphids, mealy bugs, etc.), treat your plants with an insecticidal soap, which you should be able to find in the Flower District or at a local garden center. The insecticidal soap will not deter the ants directly, but hopefully it will wipe out any food sources that might be present and they won't be so inclined to stick around. As far as a treatment for the ants themselves, I am sorry to say I do not have a quick answer right now. We have some text here in the Library so I will review that and see what we come up with. Given this day and age I'd probably do some Google searches too and see what others recommend.