Most annual flowers and small vegetables will grow in containers from 5-inch pots to gallon or larger sized containers. Larger vegetables, such as dwarf tomatoes, peppers, or cucumbers will require 1 to 3 gallon containers. Fertilizer Since potting mixes drain water rapidly, causing fertilizer to be washed out of the containers as you water, you will need to replace lost fertilizer. Lighter mixes will require more frequent fertilizing than heavier mixes containing soil. Remember, you are growing a plant with a small, constricted root system so regular fertilizing and watering is important.
Many gardeners prefer to apply a dilute water-soluble fertilizer solution at every other watering.
There are several water-soluble fertilizer materials available at your garden supply dealer, including Rapid Grow, Hyponex, Miracle Grow, and other products. If you fertilize at every other watering, use only one-fourth the recommended rate unless the instructions state directions for continuous feeding for container gardening. Controlled release or time release fertilizers are also becoming widely available. These are pellets designed to release fertilizer gradually over a long period of time. Use these according to directions on the package label.