Many gardeners use the concept of "thriller-filler-spiller" when building their summer baskets and container planters, but as is true with any simplified idea, it's not always black and white. Calibrachoas, also known as Million Bells, can fulfill all three functions, depending upon the size of the planters, the specific varieties used, and what you choose to combine with them. 'Hula Amethyst' is a great "blender" with two shades of purple and a yellow throat, opening the door to a broad spectrum of complementing colors. Mounding up to 10 inches tall, this variety also fills baskets and containers nicely with dark green foliage and spills over edges. Place calibrachoas in a sunny location, and water and fertilize regularly for beautiful blooms right up until frost.