Planting flower boxes is a type of container gardening. A flower box is typically a rectangular or square shape, but it can be any shape. It may be mounted on brackets along a deck or fence, or you might use a flower box to edge a patio or pool. Flower boxes are sometimes mounted outside a window sill as window boxes. They are an excellent way to create growing space where there was none before.
A flower box can be made from just about any weatherproof material. Brick or stone built-in patio planters are permanent installations, but you might also choose lightweight plastic or fiberglass boxes. Flower box planters are molded from terracotta and concrete, or you can make your own from wood.
A flower box should be at least 9 inches deep and 8 inches across, with a length appropriate for its location. Staple heavy construction plastic or pond liner material to the inside of a wooden box to make a leak-proof liner. Place a large flower box where you want it to remain before you fill it with soil. A 9-by-8-inch by 4-foot fiberglass flower box might weigh 100 pounds or more once it is filled with soil and plants.
Many European buildings are adorned with window boxes. Americans are beginning to revive this kind of charming flower box. A window box is mounted on brackets that are bolted to the wall studs of the house. East or west walls are good locations for window boxes, so they will have morning or afternoon sun. A south-facing window box will receive full sun all day and will need extra watering. North-facing window boxes are fine for shade-loving plants.
Planting a Flower Box
Select the flowers and foliage plants you want to use in your flower box. Add some smooth stones for drainage in the bottom of the box and a shallow layer of compost and potting soil mix. With the plants still in their pots, practice the arrangement you would like in the box. When you are satisfied with the placement, remove the plants from the pots one by one and place them in the flower box, beginning at one end and working toward the other. Fill spaces between the plants with more soil as you go.
Any plant that grows well in a pot will grow nicely in a flower box. New varieties, such as the WAVE® petunias, were developed for containers and will bloom all season long. Use some upright flowers that like sun, such as geraniums, French marigolds, dwarf zinnias or salvia, or plant some “drooping” flowers, such as impatiens or begonias, for shady locations. Fill between the flowers with trailing verbena or vinca, or add colored foliage like coleus.
A small flower box will fit on a window sill indoors. This is one way to grow fresh culinary herbs in your kitchen window.