Gardening, whether in ground or in containers, outdoors or indoors, requires four things to maintain healthy plants: growing medium, light, water, and nutrients. As long as you have those things, you’re on your way to being a gardener!
If you have space constraints, or you’re moving at some point and don’t want to walk away from your work, or if you don’t have an outdoor area with growing medium, or if you want to grow indoors, container gardening might be just the perfect thing for you. I choose to grow primarily in containers because I move every few years and like to take my plants with me. Some people garden with containers in water, which is generally called hydroponics. Others, like me, focus on containers filled with soil, because I primarily grow plants that naturally grow in soil and I think they deserve that natural medium. This is the style of container gardening on which this series will focus.
Perhaps the first thing to consider with container gardening is how much soil you’ll need and what size container is best. For a plant which is currently smaller but will grow larger, start with a smaller container and increase as necessary.

This plant is a young (1st year) blackberry plant that I started from a root cutting off a larger shrub. It is, consequently, in a smaller container than its parent plant (3 years old).

There they are next to each other. If you give a smaller plant a larger container straight off, its roots will never reach the water that will pond in the soil at the bottom of the pot. This can cause all sorts of problems from rot to bad fungus to insect infestation. As your plant grows, increase its pot size once a year or when you see the ends of the roots peaking through the drain holes. Repot to a container roughly a half size bigger than the current container, or no more than twice as big. You want enough room and fresh soil for the roots to spread and delve, but not too much room that you’ll have lingering water.