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. 'Minifamous Double White is often used to make brighter colors pop, but it can add an elegance to any container on its own. Reaching about 12" in height at maturity, it can fill a small pot all by itself, or trail over the edge of larger pots with taller centerpieces. Calibrachoas bloom best in sunny locations with regular watering and fertilizing, pushing out flowers right up until freeze.