Vegetables in Containers Require Enough Sun, Space, Drainage

by Kathryn L. Arthurs.

Kathryn L. Arthurs is a garden writer/ editor for a Western publishing company. She lives in Palo Alto, Calif.

Growing vegetables in containers can be fun as well as challenging, and for those of us with little or no ground space available it provides a good alternative. All you need to grow container vegetables is enough sun and adequate space for a good-sized container.

Most types of vegetables lend themselves to container gardening. All you have to do is find the varieties that have been hybridized for container growth, or those that can be adapted to confined quarters. Some crops like corn that produce large root systems will need a very big container. Other plants with indeterminate growth habits such as pole beans, cucumbers, and tomatoes require a support system. Still other vegetables will grow in average-size pots or in hanging baskets.

Container-grown vegetables make few demands when it comes to location. Absolute requirements are 5 hours or more of full sun, enough space to set the container, and adequate air circulation. A nearby water supply equipped with a hose and a soaker/sprayer nozzle attachment is a real convenience, but not essential.

Once these demands are met, you can place containers anywhere on a patio or deck, terrace, balcony, window box, garage roof, walkway. If you have no available ground space, consider growing vegetables in hanging baskets.

Drainage can be a problem in container gardening. With smaller containers, wherever possible use drip saucers to catch excess water. A large container without a saucer that sits directly on a solid surface (a cement or brick patio, for instance) may benefit from being elevated slightly. If the container stays in contact with a solid surface, water can accumulate, causing root rot as well as possibly staining the patio surface. You can use short lengths of wood to raise the pots one or two inches off the patio.

Types of Containers

Large containers are the best for growing vegetables. As long as the plants have ample root space, you can introduce most vegetables that normally grow in the ground.

For growing vegetables, a minimum-size container is a 6-inch diameter pot with a soil depth of 8 inches. This size can sustain lettuce, herbs, peppers, radishes, and other shallow-rooted vegetables. Root crops such as beets, carrots, radishes, and turnips need depth and enough surface space to fill out to their mature size. Thinning these crops will be essential.

Each vegetable determines the best size and style container it needs for an adequate harvest. Very large containers are required for regular-size tomatoes, for squash, pole beans, cucumbers, and corn. Half barrels, wooden tubs, or large pressed paper containers work well.

Adequate drainage is another requirement for growing vegetables in containers. Most commercial containers come with drainage holes, but you may find these insufficient. Since most vegetables in containers need daily watering, and fast draining is crucial, consider increasing the size or number of the drainage holes or slots. Wooden containers can have new drainage holes drilled. Existing holes in clay and ceramic pots can be enlarged by carefully chipping away the edges, or additional ones may be drilled with a masonry bit.

Stair-step benches hold containers filled with vegetables. Sunny brick patio is ideal location.

If a container lacks drainage holes, you can provide a drainage layer of rocks, pebbles, or pot shards to hold any excess water until it can be used or evaporated. Since vegetables need daily watering (depending on the individual plant and your climate), the drainage layer should fill from a quarter to a third of the total container volume. Keep in mind that this drainage layer won't guarantee success; containers with ample drainage holes are best for growing vegetables.

There are many types of containers you can purchase or make yourself that can be used for growing vegetables: red clay pots, wooden containers, pressed paper pots, plastic pots, and raised beds. Each type has advantages and drawbacks. Study your individual needs carefully, then select the containers that best meet them.

The container gardener's stand-by, red clay pots, have much to recommend them. They are readily available in a wide range of sizes and shapes; they are porous, allowing excess moisture to evaporate through their sides; they "weather" well; and their weight keeps them from being top-heavy. They are attractive and blend into most garden or patio designs.

On the minus side, clay pots are breakable and expensive. Filled with damp soil, large pots will be heavy and difficult to move. Their porosity lets the potting mix dry out quickly, requiring more frequent watering.

Tubs, half barrels (originally used to age wine or whiskey), rectangular or square boxes, and hanging slatted baskets all come in wood. Redwood is probably the most commonly used type of wood, with cedar a close second. Both woods resist damage by termites and "weather" well. Wood, like clay, is porous.

Wooden containers are available in a wide variety of sizes and shapes and are relatively inexpensive. Some wooden containers will deteriorate; those that are reinforced with metal bands are sturdier than containers held together with nails or glue. Like clay pots, half barrels and large tubs will weigh a lot when planted. Check plants in wooden containers daily for water needs.

Pressed paper pots, a recent innovation in plant containers, come in many sizes, are inexpensive and lightweight. Their weight can be a disadvantage if wind is a problem or if the vegetables grown in them are top-heavy.

Plastic is a common material used in smaller containers and hangers. Plastic pots are lightweight, inexpensive and non-porous. Most plastic containers come in green or white, colors that can be visually jarring in a garden. They are breakable.

Since plastic pots are non-porous, moisture is retained in the potting mix. This will be a problem only if drainage holes are inadequate or you tend to over-water. Plastic hanging baskets make good choices because of their weight and water retention. Hanging plants dry out more quickly than other container plants and need a firm support to hang from.

A raised bed lacks one of the basic qualifications for container gardening: it is stationary. It does, however, restrict the growing area and provide for good drainage.