Planter boxes are a space-saving and design solution for many gardeners. Planter boxes can be portable, allowing them to be moved from sun to shade as needed. They can also be raised for easier flower management. When choosing flowers for the planter box, choose groups of plants with approximately the same growing needs. Moisture requirements, nutrients and sun exposure should match so that all of the flowers can thrive. The size of the planter will also be a factor when choosing flowers, for both design and safety.
Choose Plants for Sun
Planter boxes in a sunny location will need to be checked more regularly for moisture content. Petunias are a favorite flower because they are available is so many varieties and colors. Other flowers that do well in planter boxes are nasturtiums, chrysanthemums and pelargonium. Consider adding a licorice plant--the woolly, silver-colored foliage adds an attractive color and texture to the planter box even after the flowers fade, and the trailing leaves can be allowed to drape over the edge of the box.
Choose Plants for Shade
Planter boxes located in the shade can give home to many flowering plants, annuals and perennials alike. Impatiens, fuchsia, cyclamen, begonia are all shade loving plants with beautiful flowers. Bring the illusion of light into a shaded planter box by choosing brightly colored flowers. Flowering shrubs like skimmia japonica will also grow well in a planter box in a shady location and serve to give a structural design element to the display.
Choose Plants for Height
Planter boxes come in all sizes, from small boxes that can be moved from a shelf to a window sill, to the huge permanent planter boxes made of stone. Choose a variety of flowers that fit the size of the container. Tall, spiky flowers like snapdragons and irises will be safer and more attractive in a large planter box while low growing flowers like begonias and petunias won't tip a shallow box over. Check the mature height of the bedding plant before purchase to be sure it will not overgrow the available space of the planter box. Planter boxes holding masses of the gardener's favorite flower can be very appealing. Other gardeners like a variety of flowers in the planter box. A large planter can hold groups of plants. Consider surrounding a tall flower like a bearded iris with groups of shorter flowers like chrysanthemums or petunias. Plant the surrounding plants in groups of uneven numbers to avoid a patchwork look in the large planter box.