Almost any vegetable, flower, herb, shrub, or small tree can grow successfully in a container. Dwarf and compact cultivars are best, especially for smaller pots. Select plants to suit the climate and the amount of sun or shade the container will receive. If you are growing fragrant plants, such as heliotrope (Heliotropium arborescens), place containers in a site protected from breezes, which will disperse the perfume.
Use your imagination, and combine upright and trailing plants, edibles, and flowers for pleasing and colorful effects. Container gardens can be enjoyed for one season and discarded, or designed to last for years. When designing permanent containers, remember that the plants will be less hardy than usual because their roots are more exposed to fluctuating air temperature. Nonhardy plants will need to have winter protection or be moved to a sheltered space. So consider how heavy the container will be and decide how you will move it before choosing a nonhardy plant.
Here are some suggestions to get you started:
Vegetables and herbs. You can grow vegetables in individual containers—from large pots to 5-gallon buckets or half barrels, the largest of which will accommodate a single tomato plant or several smaller vegetables such as broccoli or cabbage. Dwarf or bush forms of larger vegetables such as tomatoes, pumpkins, and winter squash are most suited to container culture. Theme gardens also are fun to try. Plant a salad garden with colorful lettuces, dwarf tomatoes, chives, and parsley. Or perhaps try a pizza garden, with different types of basil, plus tomatoes and peppers. Or plant a container with edible flowers such as marigolds, pansies (Viola × wittrockiana), and nasturtiums (Tropaeolum majus).
Annuals. For containers that remain attractive all summer long, look for warm-weather annuals that bloom all summer or have foliage that remains attractive. Geraniums, marigolds, wax begonias, coleus (Solenostemon scutellarioides), scarlet sage (Salvia splendens), and flowering tobaccos (Nicotiana spp.) are all good choices, but you will find many, many more in garden centers and seed catalogs. Experiment, and if one plant doesn't work out, don't worry about it—just cut it down and try something else. For large containers, dwarf cannas and dwarf dahlias also make satisfying additions.
Perennials and shrubs. Containers planted with hardy perennials and shrubs can be grown and enjoyed from year to year. Hostas and daylilies are great container plants, but many other perennials work as well. Try ferns, European wild ginger (Asarum europaeum), sedges (Carex spp.), lavender, lamiums (Lamium maculatum), sedums, and lungworts (Pulmonaria spp.). Ornamental grasses are great in containers, too, as are dwarf conifers and small shrubs.
Caring for Container Plants
Water container plants thoroughly. How often depends on many factors such as weather, plant size, and pot size. Don't let soil in containers dry out completely, as it is hard to rewet. To keep large containers attractive, spread a layer of mulch as you would in the garden. This will also help retain moisture. Be sure to keep mulch an inch or so away from plant stems.
Container plants need regular feeding. Fertilize them by watering with diluted fish emulsion, seaweed extract, or compost tea. Or foliar feed by spraying the leaves with doubly diluted preparations of these solutions. Start by feeding once every 2 weeks; adjust the frequency depending on plant response.
Since containers are focal points in the garden, you will probably want to give them special attention to keep them looking their best. Remove tattered leaves and deadhead spent flowers. Prune back plants that get leggy or stop blooming. To keep mixed pots attractive, dig out or cut back any plants that don't grow well or that clash. You can add something else or let other plants in the container fill the space. Keep an eye out for pests like aphids and mites.