(News article for April 10, 2020; updated 4/11/22)
Not everyone has a large, sunny yard in which to grow vegetables, and some people who do may not have the desire, equipment, or physical ability to cultivate a large garden in the ground.
A raised bed is often a good option for home gardens. They allow for better drainage in areas that have poor surface drainage or a water table close to the surface, and they can help make weed management easier. They can also help make gardening easier on one’s back.
But what about people who just have a sunny patio or don’t want to take on more than a few plants? Just about any vegetable can be grown in some type of container.
Some vegetables need larger containers than others. Among warm-season vegetables, tomatoes, peppers, eggplants, and squash will need relatively large containers (approximately 5 gallons or more), while cucumbers and beans, for example, can be grown in smaller containers.
One of the first things to remember when growing anything – edible or ornamental – in a container is that the container needs to drain well. It should have holes at the bottom, and the planting medium in the container needs to allow water to move through it easily. Potting soil rather than topsoil or soil from the garden should be used.
If you want to keep it really simple, you can lay a bag of potting soil on the ground, make several holes or slits near the bottoms of the sides, cut one or more openings on the top (depending on what you’re growing and how much space is needed between plants), and plant directly into the potting soil.
It’s probably easiest to just buy potting soil, although there are various ways to make your own. For example, you can combine soil, compost, and either sand or perlite in equal parts. We want something that retains enough water but not too much. If you mix your own, the pH of the mixture may need to be adjusted to bring it to around pH 6.5.
Many potting mixes will have fertilizer mixed into them. Fertilizers in newly opened potting mixes may provide nutrients over the course of several weeks or a couple of months. Vegetables that have a high nutrient demand, like tomatoes, will likely need some supplemental fertilizer, though. Soluble fertilizers like Miracle-Gro can be used. For fruiting vegetables like tomatoes, peppers, squash, and cucumbers, try to find one in which the concentrations of phosphate and potash are greater – or at least as great as – that of nitrogen.
One thing to note is that fertilizers that we dissolve in water before use typically do not contain calcium. All plants need this nutrient, and some – including tomatoes, peppers, and watermelons – will get blossom end rot if they don’t have enough. If you’re reusing potting soil or making your own, you may need to add calcium to the potting soil. Gypsum provides both calcium and sulfur and can be mixed into potting soil at a rate of 6 tablespoons per cubic foot or 2.5 teaspoons per gallon.
Some varieties of vegetables are better suited to container production than others. If you’re growing tomatoes, you might want to choose a determinate or bush variety, like ‘Celebrity’ or ‘Bella Rosa’, rather than an indeterminate or vining variety. Determinate or bush varieties grow to several feet tall and then stop growing vertically. Indeterminate varieties, like ‘Big Beef’ and ‘Better Boy’, can keep growing vertically as long as they’re given structural support and not limited by frost, disease, nutrients, water, etc.
Likewise, when choosing snap or lima beans for containers, you may want to go with a bush variety rather than a vining or pole variety.
If you do grow plants that need support, you may be able to place your containers next to a fence or rig up a make-shift fence with something like u-posts and welded wire fencing.
Containerized plants will need regular water (likely once or twice per day) if it doesn’t rain. To determine if plants need to be watered, you can stick your finger in the potting soil and see if it’s dry at one-half inch deep. When you water plants in containers, do so until some water runs out of the holes at the bottom.
The cost-effectiveness of container gardening is sometimes questionable. If you buy a new decorative pot and new potting soil, the costs of these things may outweigh the value of the vegetables produced in the container. However, there are ways to make container gardening more cost-effective, such as by reusing potting soil and containers.
If you’re using potting soil that’s been used before or including soil from the ground in a mixture, it’s best to pasteurize it before using it. This can be done by heating an oven to 180 °F, placing moist soil in a shallow pan, covering it with aluminum foil, inserting a meat or candy thermometer into the soil, and allowing the soil to remain at 180 °F for 30 minutes after it reaches that temperature. Yes, your oven may have a different smell after this process is complete.
Containers can be disinfected using a solution of bleach and water. First clean soil from the containers and then soak containers in a bleach solution, according to label directions.
Let me know if you have questions.
(Also see this article about vegetable gardening resources.)
Contact Mary Helen Ferguson.