I too don't think ants harm plants, but they are unaesthetic. My outside plants, particularly my staghorn ferns will sometimes end up with ants, and these are usually what I call "sugar-ants". Before I bring them in I put just a pinch of Orthene Fire Ant Killer on the potting material and the ants will be eliminated within 24 hours. I think the boric acid solution would be very effective as well, and without the odor of Orthene powder. I simply hose the plants down with water to eliminate the Orthene before bringing them in for the winter.
