I have grown Elecampane, Inula helenium, for years but never realized until this summer that Elecampane had a special relationship with ants. While the buds were getting fat and preparing to bloom, they were guarded by a swarm of ants. "Ants???," you say. "Most definitely," says I. And while I could not find a specific reference to Elecampane having these special structures, the presence of the ants tells me it is there - extrafloral nectaries. Extrafloral nectaries are special nectar producing glands located outside of the flower and unlike the nectar produced in flowers, this nectar has nothing to do with pollination and reproduction. In fact, it is to entice bodyguards who help discourage herbivores.
Peonies are very common plants to see this mutually beneficial plant - ant relationship on. You do not to spray the ants off your peonies or Elecampane with water or any bug repellents because the plant has put out a place setting for its ant friends and will only benefit from their presence.