Plants that will grow in small containers must be chosen carefully. The plants should have small root systems so they won't be cramped, and they should have small flowers and leaves so they don't appear top-heavy and overwhelm their containers. Almost any kind of container works for a small plant, as long as the container has bottom drainage holes and is large enough to hold at least 1 to 3 gallons of potting soil.
Several varieties of annual vegetables grow well in small containers. Leafy greens, such as lettuce (Lactuca spp), and small root vegetables, including radish (Raphanus sativus), grow well in containers when their soil remains moist. Dwarf varieties of other vegetables also are suitable for small containers. They include the tomato (Solanum lycopersicum) cultivars "Tiny Tim" and "Patio." Vegetable plants need well-drained soil kept moist with regular watering.
Most herbs grow best in a loose, well-drained potting mix and don't require as much water as vegetable plants. Each herb plant needs about 1 gallon of potting soil. So multiple herb plants can grow in one pot that holds 2 or more gallons. The best herbs for containers are compact rather than tall. Two options are dwarf cultivars of basil (Ocimum basilicum) and German chamomile (Matricaria recutita), which are both annual herbs. Perennial herbs for containers include English lavender (Lavandula angustifolia), which is hardy in U.S. Department of Agriculture plant hardiness zones 6 through 9, and sage (Salvia officinalis), hardy in USDA zones 4 through 8.
Most flowering annual bedding plants can be grown in small containers. Just check the plant labels when shopping to ensure flowering annuals' mature sizes will not overwhelm your containers. A plant's mature size should be no more than three times the plant container's height. Petunias (Petunia x hybrida), dwarf snapdragons (Antirrhinum majus), geraniums (Pelargonium x hortorum), dwarf French marigolds (Tagetes patula) and sweet alyssum (Lobularia maritima) are flowering annuals that can grow in small containers. Because small containers dry out more quickly than larger containers, check the plants' soil every day, and add water if the soil feels dry to your touch.
Some of the perennial plants that grow well in small containers are three-veined everlasting (Anaphalis triplinervis), which is hardy in USDA zones 3 through 8, and heart-leaved bergenia (Bergenia cordifolia), hardy in USDA zones 3 through 9. Both of those plants reach 12 to 18 inches tall. Low-growing ground covers also work well in a small container and can be paired with a taller perennial if the container is big enough for two plants. Keep perennial plants' soil moist during the growing season. Container-grown perennials should be overwintered indoors to keep their soil from freezing. A wintertime temperature of 50 degrees Fahrenheit is ideal for most perennial plants.