Window boxes, outdoor planters and flowerpots provide green-thumb enthusiasts with creative options beyond the standard flower garden. They increase the aesthetic appeal of many flowers, brighten an entryway and provide space-limited gardeners with a workable medium. However, the design principles of a garden do not apply to pots, and gardeners must do some homework before throwing a group of plants together in one container. When it comes to arranging flowers in an outdoor flowerpot, think interior decorating as opposed to standard horticultural design.
Find a pair. As with indoor decorating, when planting outdoor pots it is important to think in terms of threes. Most people prefer to use two flowers that are similar in color and texture and one focal plant. To implement this, find two plants that are similar and complement each other. They should be roughly the same height and width and have blooms similar in size and color. According to "Pots in the Garden: Expert Design and Planting Techniques," it is also aesthetically appealing to have three pots filled with the same plants and grouped together.
Get focused on the focal plant. This plant should stand out above and beyond the paired combination. Green foliage—such as a coleus—is often used for this purpose. However, a wave petunia or other trailing plant may be your preference. If using three plants, place the focal flower between the pair. If using five, place the focal flower between two sets of two.
Arrange the plants in the pot according to how you want them to grow and fill in with dirt.
Water the arrangement well. Just-planted roots need to take hold of their new surroundings, and there is no better way to encourage this than by starting them out with a long drink.