The best containers for container gardening are ones you not only find attractive but ones that also create a good growing environment for the plant. Any plant can be grown in a container that is of the appropriate size for the plant, has good drainage and is made of a durable material. The best containers will contain an adequate amount of soil for plants to reach their optimal size and performance.
Container Size and Material
All containers must be of a durable material so moist soil does not cause the container's walls to collapse or rot. Choose containers that are of a weight that you can safely lift or move. Concrete or stone containers are extremely durable but are quite heavy. Fiberglass, vinyl, resin or other modern composite containers are sturdy but of minimal weight. Metal containers may rust, and metal conducts heat and cold quickly, sometimes to the detriment of the plants. Clay and plastic pots are universally popular. Clay pots are porous and sturdy, but they may crack in the extreme cold and the soil can dry out very quickly. Plastic pots are inexpensive, lightweight and durable in comparison and do not dehydrate soil. Regardless of the material, containers must be of a size that houses enough potting soil to sustain the plant's expected mature size.
There are concerns regarding the leaching of toxins from containers made of treated lumber and recycled vehicle tires. Never grow edible plants in containers made of questionable materials.
Each garden container needs drainage holes in its bottom or the plant will succumb to rot and will eventually die from water and salt buildup. Holes of at least 1/4 inch are ideal, as they are easy to see, clean and unplug. Larger holes may allow soil to wash out, whereas very small holes can become clogged by soil particles or not let water escape fast enough.
In general, container shape is not important, but certain container forms can lead to plant maintenance issues. The soil in small and shallow containers will dry out more quickly; those in large, deep containers hold and retain moisture longer.
Containers that are wider at their bottoms and mid-sections and narrower at their tops can be problematic. Once plants fill out and expand their roots below the narrow rims, it becomes extremely difficult to remove plants and soil through the narrow neck. If you choose an attractive container with a narrow neck, the only option to remove a plant may be to break the container or invest a lot of time and labor to remove the plant and its large root ball in many small pieces.