If you aren't sure about what size container to choose, it is best to err on the larger side.
Choosing the right size container means choosing the size pot that will support a productive, full-sized plant. You must also consider the weight, cost, and your ability to water. You can grow a single tomato plant for a season in an 18- to 20-inch pot or a half-barrel. A basil plant will be happy in a 16-to 18-inch pot. A thyme might be happy in a 10-inch pot if you can keep it watered.
However, if you want to be more creative or limit your number of pots, buy a significantly larger container to combine several kinds of vegetables, herbs, and flowers. You can surround an upright tomato with a ring of chives at the edge of the pot, or combine a tomato, basil, parsley, and onions in a 24-inch or larger container. A large strawberry jar with deep pockets is perfect for herbs and leaf lettuce.
Keep in mind that not all pots are round and tall. Shallow-rooted plants such as lettuce will be happy in a bowl, that is, a pot that is wider than it is tall. However, most vegetables will need a deeper pot. Broad plants such as a zucchini or pumpkin will benefit from a pot that is both broad and deep. Half-barrels are perfect for bigger plants such as tomatoes and squash. Use your best judgment to give your plants plenty of room for optimum harvests. Sometimes experience provides the best advice for the future.
