Pots, tubs, and half barrels overflowing with flowers add appeal to any garden, but container gardens can serve a practical purpose too. Gardening in containers is ideal for those with little or no garden space. In addition to growing flowers, gardeners limited to a balcony, small yard, or only a patch of sun on their driveway can produce a wide variety of vegetable crops in containers. Basil, chives, thyme, and other herbs also are quite happy growing in pots, which can be set in a convenient spot right outside the kitchen door.
Container plants also add versatility to gardens large and small. They lend instant color, provide a focal point in the garden, or tie in the architecture of the house to the garden. Place them on the ground or on a pedestal, mount them on a windowsill, or hang them from your porch. A pair of matching containers on either side of the front walk serves as a welcoming decoration, while containers on a deck or patio can add color and ambiance to such outdoor sitting areas. You can use single large containers for outdoor decoration, but also consider arranging groups of pots, both small and large, on stairways, terraces, or anywhere in the garden. Clusters of pots can contain a collection of favorite plants—hen-and-chicks (Sempervivum spp.) or herbs used both for ornament and for cooking, for example—or they may feature annuals, dwarf evergreens, perennials, or any other plants you'd like to try. Houseplants summering outdoors in the shade also make a handsome addition to container gardens. Window boxes and hanging baskets offer even more ways to add instant color and appeal.
Containers planted with a single species—rosemary (Rosmarinus officinalis) or a bold variegated ornamental grass, for example—can be stunning garden accents. Containers planted with a mix of plants are fun to create and offer almost unlimited possibilities of combinations. The best combinations depend on plants that feature handsome foliage and flowers produced over a long bloom season. One easy guideline for choosing the plants to combine in a container is to include "a thriller, a spiller, and a filler." That translates to at least one focal-point plant (the thriller), such as coleus or a geranium with multicolored leaves, for example, combined with several plants that spill over the edge of the pots—such as petunias, bacopa (Bacopa spp.), creeping zinnias (Sanvitallia procumbens), or ornamental sweet potatoes (Ipomoea batatas 'Blackie'). Finally, add the fillers, which are plants with smaller leaves and flowers that add color and fill in the arrangement all season long. Good fillers include salvias (Salvia spp.), verbenas (Verbena spp.), ornamental peppers (Capsicum spp.), and wax begonias (Begonia semperflorens) as well as foliage plants like parsley or licorice plants (Helichrysum spp.). You may also want to include a plant for height, such as an ornamental grass like purple fountain grass (Pennisetum setaceum 'Purpureum'). Add a trellis or pillar to a container and you can use a vine to add height to the composition. You'll need a total of five or six plants for an 18- or 24-inch container, for example.
Pots and planters come in a wide range of sizes, shapes, materials, and styles. You can also modify everyday containers such as bowls or barrels to be planters.
Size: When choosing a container, keep in mind that it's easier to grow plants in large containers than small ones. That's because large containers hold more soil, which stays moist longer and is less subject to rapid temperature fluctuations. Small hanging baskets are especially prone to drying out, and during hot summer weather, you may have to water them twice a day to keep plants alive.
It's also important to decide what plant you want to grow in each container. Several factors help determine how large and deep the container must be. Consider the size and shape of a plant's root system; whether it is a perennial, annual, or shrub; and how rapidly it grows. Rootbound plants, which have filled up every square inch of the soil available, dry out rapidly and won't grow well. Choose a large pot or tub for a mixed planting, one that will offer enough root space for all the plants you want to grow. Light-colored containers keep the soil cooler than dark containers.
The maximum size (and weight) of a container is limited by how much room you have, what will support it, and whether or not you plan to move it. If your container garden is located on a balcony or deck, be sure to check how much weight the structure will safely hold.
Drainage: Whatever container you choose, drainage holes are essential. Without drainage, soil will become waterlogged and plants may die. The holes need not be large, but there must be enough so that excess water can drain out. If a container has no holes, try drilling some yourself. A container without holes is best used as a cachepot, or cover, to hide a plain pot. Cachepots (with holes and without them) are useful for managing large plants and heavy pots: Grow your plant in an ordinary nursery pot that fits inside a decorative cachepot so you can move them separately.
Self-watering, double-walled containers, hanging baskets, and window boxes are available. These are a useful option for dealing with smaller plants that need frequent watering.