Gardening in Containers
Pay heed to their few special requirements. With practice, most popular vegetables grow in containers placed on your deck, balcony, patio, or walkway. Containers even have a place in raised-bed or open-soil gardens: They add new planting space and visual interest to home vegetable gardens.
First, choose a container large enough for the plants you wish to grow. Many vegetables grown in garden soil are deep rooted. Sweet corn, for instance, has roots that extend 3 ft. (90 cm) or more. Tomatoes grow roots as deep as 4 ft. (1.2 m), and the lowly beet and parsnip often extends roots into the soil 10 ft. (3 m) or more. Still, many of these are easily grown in much shallower soil as long as it is kept rich with nutrients and has proper drainage.
Container Size
For most vegetables, choose pots that are at least 18 in. (45 cm) deep. They must be sufficiently wide to accommodate stakes or other supports for tall or vining plants. Containers also should be as large in diameter as the recommended between-plant spacing for the vegetable species they’ll hold.
Select containers with adequate drain holes. Many pots are available with only a single hole that is just 1/4 in. (6 mm) wide or smaller. Enlarge existing drain holes or add more drains prior to planting [see Choosing and Preparing Containers].
Container Types and Materials
Containers come in a variety of materials, including concrete, glazed clay pottery, stone, unglazed terra cotta, and wood, as well as plastic and various other synthetic materials. Each material has its own pluses and minuses.
Concrete and stone planters are another option, durable, porous, and offering insulation from overheating. Remember that salts leaching from concrete and such natural stones as limestone or marble can alter soil chemistry in the container. Because concrete and stone are heavy, they’re best suited to ground-level containers.
Plastic pots are lightweight and economical, though they vary in durability, porosity, and their ability to insulate the soil within. Avoid those with built-in watering reservoirs.
Unglazed terra cotta pots are another popular option. They are moderate in weight, insulate well, are very porous, and are economical. Their one downside is being subject to drying due to evaporation, unless you treat them with waterproof sealant.
Glazed clay pottery is light, waterproof, and quite durable if handled with care; it is subject to breakage and often is less economical than other materials.
Wooden planters have the benefits of being natural, offering good insulation, and having good porosity; seal wood containers to protect them from fungal rot.
Some woods may stain walks or patios, and fungal growth in the damp areas beneath pots also discolor concrete surfaces. Always use so-called pot feet, bricks, or other risers placed under the pots to keep them raised above the soil or installation surface and provide access beneath them for cleaning.
Pre-Planting Preparation
Before you plant, always protect drain holes from clogging or from roots blocking their openings. Line the pot with porous landscape fabric set over pea gravel or cover drain holes with plastic mesh or broken pottery shards.
Next add 1 in. (25 mm) of pea gravel above these filtering materials. Such preventive measures help stop loose potting soil from washing down into the drains, but still allow water to pass through the drain holes so that the soil the container holds remains moist but not soggy.