There are many choices. It really depends on the size of the planter boxes and the season. For now some marigolds would be nice. When frost kills them switch to pansies, viola, alyssum, or dwarf snapdragons. In spring try petunias, blackfoot daisy, dahlberg daisy, pentas, and 'Stary Eyess Nierembergia. These are all sun to mostly sun plants. If your planters are in shade please submit another question to the Monrovia website indicating that.
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