Flowers are frequently grown in containers, but vegetables may also be grown in this way. This makes vegetable gardening possible for those who do not have the ground to work in. Gardening from a patio, balcony or porch is possible. Containers are a way to garden even if your outdoor soil has become contaminated or is of poor quality. Tomatoes, peppers, eggplant, green onions, beans, lettuce, squash, radishes and herbs may be grown in containers if a smaller variety is chosen and a large enough container is used. Vining plants like peas, beans or cucumbers may also be grown in containers if a vine support is added to the container.
After choosing the vegetable, select a container large enough to support the full-grown plant. Often this will be a gallon pot or larger. Any container that will hold soil and water may be used. Containers which are wide as well as deep are important for those plants whose roots spread horizontally. Some vegetables may need a five-gallon pail to grow well.
Container-grown plants require more frequent watering than those grown in soil, but they do not want their roots sitting in water, so drainage holes are required. A drip tray or saucer is also a good idea to prevent water stains from occurring on the surface the container is placed on. Even, consistent watering is important — especially for tomatoes — to prevent blossom end rot and other problems.
Place the container in a location where it will not have to be moved. Once the container has been filled with soil and the plant has grown and been watered, the container will likely be quite heavy. Gardeners who grow annuals in containers may place gravel, Styrofoam or sealed containers in the bottom of the container to keep containers from becoming too heavy. This practice is not recommended for vegetable growing because most vegetables have more roots and need more below-ground growing space than annuals.
Containers which need to be moved to follow the sun may be placed on wheels. However, those wheels may also make it possible for the container to be moved by a strong wind. Vegetables usually need full sun to grow which means six hours or more of sun each day (although eight hours is preferred — especially for warm-season crops). Cool season crops, such as lettuce or spinach, may grow with less than six hours of full sun each day.
The seed envelope or instructions included with a vegetable plant will inform the gardener whether the plant may be planted before the last frost or not. Seeds for warm season vegetables may be started, or plants placed in containers before the last frost if the container can be moved indoors at night.
Purchased potting soil is recommended for container use because it is lighter than garden soil and is often mixed with compost, perlite, or vermiculite to promote drainage. Fertilize the plants with fertilizer recommended for vegetable growing; but use half the amount recommended on the package. Additional fertilizer may be added if needed, but removing excess fertilizer is difficult and may kill the plant.
An online search for “container vegetable gardening” will supply additional details from several state extension sources.
Linda G. Tenneson is a University of Minnesota master gardener and tree care advisor.