Container gardeners are devoted to their craft for many reasons: Some have no land to cultivate; others just prefer to contain their gardening adventures to ceramic bowls, clay pots, and hanging baskets. Gardeners who move often like taking their gardens with them to their new residences. Still others like the ease of container gardening. There's less weeding and stooping, for example, and plants in containers are generally less susceptible to pests and diseases.
The biggest advantage of container gardens -- with the exception of most window boxes -- is their mobility. If your container tomatoes do poorly in a back corner of your yard, you can move them into brighter sunlight. And if your morning-glories wither in strong afternoon sunlight, you are free to reposition them so they get a respite in partial shade.
You can also take advantage of mobility to rotate containers frequently so every side of a potted plant receives equal sunshine for equal growth. You can even mix and match container plants to provide new arrangements as often as you're inclined. Try, for instance, a pot of dwarf sunflowers, some brilliant geraniums, or one dramatic hibiscus plant as a porch display.
Consider all container choices: stone urns, half whiskey barrels, troughs, and containers made of concrete, terra-cotta, clay, or lightweight synthetic materials. Some homeowners have created small water gardens in old claw-foot bathtubs or have used hollowed-out logs to create a miniature, rustic landscape. The choices are limited only by imagination.
When choosing containers, make sure they will be the right size for the plants you want to grow. Slow-growing plants such as conifers, evergreens, cactus, and succulents generally will be happy in containers equal to the volume of the plant. Faster-growing perennials, annuals, and many vegetables should be overpotted to accommodate root growth.
Consider plastic containers (and dollies to move them) for larger plants such as fruit trees, which in northern climates need to be moved into a garage or other sheltered place in the winter. Several large containers or many smaller ones, especially after absorbing a heavy rainfall, may put undue stress on a balcony, a rooftop, or areas of decks away from supporting posts. And watch out for the heat: Dark-color containers sear a plant's roots in areas prone to blistering hot summer days. Metal containers may also conduct too much heat and often don't hold up under the corrosive effects of salts in fertilizers.
Scale is very important to overall success in any landscape. Many beginning container gardeners make a mistake by placing pots too low, where they get lost against a busy or conflicting background. Vary your levels by placing some plants on sturdy pedestal, benches, or stairs. Suspend hanging baskets at chest level, where people can see them, or more than 6 feet high, where there is no danger of bumping into them. Plants at waist level or lower should be located off beaten paths and out of the way of rambunctious pets and children. As a practical matter, you may want to group and locate containers to ease watering.
Virtually any form of flowering or foliage plant and compact vegetables or edible herbs will feel at home in a container if you provide the proper conditions for growth. First of all, there must be drainage. Most ready-made containers have one or more holes in the bottom to provide good drainage. Drill holes, if possible, in containers you've made or found. Layer shards of terra-cotta pots or pebbles on the bottom so roots won't clog drainage holes.
Instead of garden soil, use soiless potting mixes, which are lighter, absorb more water, and drain better. Potting soils made mostly of peat moss and vermiculite are usually sold in small packages and can get expensive if bought on a large scale. Less expensive planter mixes are made of composted materials and peat moss, and should contain perlite, a gritty white material that promotes fast drainage. Use planter mixes for containers larger than 6 or 8 inches in diameter.
About three weeks after putting plants in containers, start using a water-soluble fertilizer (15-30-15, which is 15 parts nitrogen, 30 parts phosphorus, and 15 parts potassium) but only one-fourth of the suggested amount. Use this weakened solution every other watering.
The amount of watering required depends on climate, varieties of plants, the sizes of their root systems, and even the types of containers. Midsummer heat can quickly turn a backyard bright spot into a microdesert. You may need to water plants in porous terra-cotta containers two or three times more often than plants in similarly sized plastic containers. In general, never let the soil get too dry or too wet.