Plants in pots depend on the gardener for nutrients. The roots cannot grow deep enough to access other nutrients from the earth in the same way that plants grown in a garden bed can. Your container plants need a good supply of nutrients in order to produce the fruit and pods you eat, but fertilizing is an important step that is often forgotten. Gardeners think that buying a good commercial soil mix will be enough to sustain the needs of their vegetable plants all season; however, this is incorrect. Veggie plants need a little boost during the season. Fruit and berry plants usually need a good fertilizing with manure or an all-purpose fertilizer in the early spring and once they start fruiting.
About a month after planting, start fertilizing your containers; continue to do so every ten days. There are some great organic fertilizers available. One option is to use a combination of liquid kelp and liquid fish fertilizer; the labels will tell you how often and the amounts they recommend for different sizes of containers. Choose organic fertilizers as they are better for your vegetables and for you. If you want to save some money, make fertilizer teas from compost or manures.
There are fewer disease and insect problems in container gardens. Plants grown in containers will avoid soil-borne pathogens, and slugs are less of a problem.
For a quick and easy fertilizer tea, fill a bucket half full of compost or hot animal manure and then fill it with water. Let the bucket sit for a day or two (overnight if you are in a hurry) and then pour out the dark brown liquid. Mix it with water in a one-to-two ratio. Use this liquid to water the plants in your containers. Fill the pail with water again and keep using the liquid until it starts becoming lighter in color; then throw the sludge into your compost and start over, making a new batch.