A container garden is a smart choice if you have limited space or your yard's soil is poor. These mini gardens require little care other than watering and fertilizing, but they do require loose, well-draining soil and plenty of room for the roots to grow. Choosing attractive containers adds to the beauty of your container garden, but choosing the right size container is more important.
Vegetables and Herbs
Some annual plants, such as lettuce (Lactuca sativa), radish (Raphanus sativus) and other salad greens have shallow roots and do not need large planters. These vegetables can be grown in hanging pots with a 6- to 10-inch diameter or tucked into window boxes. Likewise, most herbs can be grown in a 4- to 6-inch pot. Larger vegetable plants, such as tomatoes (Solanum lycopersicum), eggplants (Solanum melongena) and cucumbers (Cucumis sativus), need a 4- to 5-gallon container to allow room for their roots to grow.
Annual flowers you buy at the garden center may be thriving in tiny pots or plant cells, but don't let this fool you into thinking they can be grown in tiny pots. Repotting them into larger pots allows their roots to grow and encourages healthy flowering. As a rule, the taller the plant is at maturity, the larger its root system will grow. Most annual flowers can be grown successfully in 10- to 12-inch pots that hold 2 to 3 gallons of soil.
Practical and Aesthetic Considerations
The size of your containers also contributes to the overall appearance of your container garden. Container gardens designed with the primary goal of producing fresh fruits or vegetables can be grown in any container with drainage, as long as it has not been used to store or transport toxic materials. When it comes to a decorative container garden, attention to the proportions of the container is important. Typically, containers that are one-third the height of the mature plant are more pleasing to the eye and showcase your blooming plants. Pots with wide, flat bottoms with relatively straight sides resist tipping in the wind better that pots with wide tops that taper to a narrow base.
Just because a plant can grow in a small container that holds the minimum amount of soil for the roots to grow doesn't always mean it is a good idea. Soil in small containers dries quickly, while a larger container may stay moist for longer. As a rule, small containers require more frequent watering than larger containers. Likewise, plants grown in containers where their roots fill most of the container absorb the water quickly, further contributing to the need to water your containers often.