keep trying)!
i always add at least 1 plant that will spill over the side.
i try to find a tall grass to put in the back (there were not any in stock when i was at the nursery buying these plants).
i shoot for a few different colors in the container. sometimes i keep the mix of flowers in the various different containers consistent and others i just grab the plants that speak to me that day (this year was a grab what speaks to me year).
i try to find plants with a mix of textures.
i look for plants of different heights. 1 or two tall plants, a spiller, and a few 