When planted singly, tomatoes require containers with a 20-inch minimum diameter. Green peppers require 16-inch diameter containers. When grown together, the two plants require containers that are usually oblong, and not round. The containers are also usually deeper than those found in garden centers. Choose non-traditional oversize containers like galvanized feeding troughs or children's wading pools with depths of at least 2 feet. Drill drainage holes if the container does not already have them. Elevate the containers above the ground to allow for better drainage. Never use containers lined with creosote or creosote-based materials as this is unhealthy for plants and, if you are eating the plants, unhealthy for you.
Any pepper plant variety is suited for container garden. Peppers have a determined growth habit -- meaning that they do not become spindly or grow out of bounds. Regardless of pepper variety the plants reach heights up to 48 inches and require up to 24 inches of space.
Tomato plants, on the other hand, can be determinant, indeterminant or a hybrid of the two. Their spacing requirements and heights vary according to cultivar. Some tomato plants are particularly tall while some continually produce until frost prevents blooms from developing. Container gardeners choose determinant varietes because of the limitations containers place on supportive root systems. Some tomato varieties suited for container gardens are: Gardener's Delight, Tiny Tim and Patio VF.
Before planting prepare your container by placing landscape cloth over the bottom and across drainage holes. This prevents soil loss. Lining container bottoms with light materials causes the containers to become top-heavy making them unstable in the event of wind or inclement weather. Site your containers in an area receiving at least six hours of direct sunlight. Peppers and tomatoes are flowering plants and require sunny locations to produce high yield harvests. The container will be heavy so ensure it is sited in the best area before filling with soil and planting crops. You may purchase rollers for the containers or build your own, if necessary.
Plant tomatoes and peppers in a container much as you would plant them in the ground. Purchase starts or start seeds indoors in small peat pots. Once the plants have lost their seed leaves and developed their own true leaves, plant them in your container. Instead of planting the starts' stems and peat pots flush with the soil level, inter them one-third or one-half deeper and loosely pile soil around the stem. This encourages shallow root development and allows the plant to grow freely within a container's confined space.