A planter box is a container used for gardening, typically elevated or placed on hard surfaces like patios, decks, and balconies. This method of gardening appeals due to its ability to maximize space, making it perfect for urban environments or homes with limited yard area. Planter boxes also offer increased accessibility, allowing gardeners to tend to plants without excessive bending, and they provide portability, meaning the entire garden can be relocated as needed.
Matching Plant Needs to Box Environment
Before choosing plants, the physical constraints of the planter box and its location must be considered. The amount of direct sunlight the box receives dictates the selection process, as most fruiting vegetables require a minimum of six to eight hours of full sun daily. Conversely, a spot that receives only three to six hours of light is better suited for partial shade-tolerant plants like leafy greens or certain flowering annuals.
The depth of the box is another factor, directly influencing root development and plant health. Shallow containers, those around six to eight inches deep, are appropriate for herbs, annual flowers, and salad greens that have confined root systems. Deeper-rooted plants, such as tomatoes, peppers, and most perennials, require a container depth of at least twelve to eighteen inches to prevent the roots from becoming restricted. Furthermore, adequate drainage is required, necessitating holes at the bottom of the box to allow excess water to escape and prevent root rot.
Top Edible Choices for Containers
Choosing edible plants that are naturally compact or specifically bred for containers ensures a successful harvest in limited space. Many herbs are ideally suited for planter boxes, including basil, chives, and thyme, which can thrive in containers as shallow as four to six inches deep. Mint, while easy to grow, should be planted in its own dedicated container, as its vigorous root system can quickly overwhelm neighboring plants.
Leafy greens are excellent choices for their fast growth and minimal depth requirements. Loose-leaf lettuce varieties, spinach, arugula, and baby kale can be repeatedly harvested using the “cut-and-come-again” method, providing a continuous supply of fresh greens. For root vegetables, success depends on selecting short, round varieties like ‘Parisian’ carrots or radishes, which mature quickly and do not require the deep soil necessary for traditional, long-rooted types.
To grow fruiting vegetables, select dwarf or “patio” varieties, as standard plants become far too large for a container. Determinate tomatoes, such as ‘Cherry Falls’ or ‘Siam Kitchen Mini’, are excellent because their growth is genetically limited, allowing them to produce fruit without excessive staking or vining. Similarly, compact eggplants like ‘Patio Baby’ and small-fruited peppers naturally maintain a manageable size, making them productive and visually appealing centerpieces in a sunny edible planter.
Flowering and Foliage Recommendations
Selecting ornamental plants based on their light needs and growth habit will ensure the planter box remains vibrant throughout the season. For areas receiving full sun, annuals that tolerate heat and bloom continuously are the best option, such as petunias (especially the self-cleaning Supertunia varieties) and SunPatiens. These plants offer a dense blanket of color and thrive in the intense heat that can build up in containers placed in direct sunlight.
In locations with partial or full shade, colorful foliage plants and shade-tolerant annuals can provide long-lasting visual interest. Begonias are excellent for brightening dark spots with their showy blooms, while impatiens are a classic choice for continuous flowering in deeply shaded areas. Foliage plants like Coleus, Hostas, and Caladium are prized for their reliable season-long color and varied textures.
Trailing plants like Sweet Potato Vine (Ipomoea) and Creeping Jenny are particularly effective for spilling over the edge of the box. These foliage choices maintain their ornamental appeal even when flowering plants slow down, providing dependable texture and contrast.
Grouping Plants for Maximum Impact
An effective strategy for creating a visually stunning planter is to combine different plant types using the “Thriller, Filler, Spiller” design concept. This technique uses plants of three distinct growth habits to create a balanced and layered arrangement. The “Thriller” is a tall, upright plant placed in the center or back of the box to act as a focal point, providing vertical drama and drawing the eye upward.
Surrounding the thriller is the “Filler,” which consists of rounded or mounding plants that add mass and volume to the midsection of the container. Fillers like compact petunias, begonias, or bushy herbs help to bridge the space between the tall focal point and the edges of the box. Finally, the “Spiller” plant is positioned near the edge, where its stems or vines cascade downward, softening the hard lines of the container.
This principle works for both ornamental and edible plantings. Beyond aesthetics, combining certain edibles can offer functional benefits, known as companion planting, such as placing basil near tomatoes to potentially enhance growth and flavor. Strategic grouping of plants with complementary needs maximizes both the visual appeal and the productive potential of the planter box.