Ageratum
They are clump-forming or mounding plants with felted or hairy, roughly oval to heart-shaped leaves with shallowly toothed or serrated edges. Flowerheads are a mass of fine filaments, usually dusky blue, lavender or pink and crowded in terminal clusters.
Best grown in full sun in moist, well-drained soil. Regular deadheading is essential to prolong the flowering. A good border plant.