Bag culture can be defined simply as growing a plant out of a bag, the same way one would utilize a plant container or a pot. But bag culture can also be defined as a method for extending or expanding the volume of media available to a plant’s root structure. In the latter scenario, an already-potted plant would be placed inside or on top of a bag filled with new grow media. The original pot would have holes in the bottom or several slits made in it so that the roots can grow down and out of the container into the extended medium of the bag. Because of these aspects, container bags are a preferred method for many greenhouse and indoor growers looking to expand root zone volume.
However, whereas bag culture can be an add-on in this way, this is not the only use for grow bags. Grow bags can be your initial, stand-alone container for individual plants or for multiple plant sites within a garden or hydroponic system.
There are many advantages of using bags as containers, including the fact that they are generally cheaper than pots—to the extent that they can be disposable with little monetary loss—though, they then have to be replaced, rather than being reused or recycled like pots can be.
Perhaps the biggest advantage, however, comes with fabric grow bags, which are more durable than plastic bags and much more breathable than plastic containers or bags. This is an especially important consideration as many new growers underestimate the importance of getting air—specifically, oxygen—to the root zone. While the green parts of the plants (above ground) breath in CO2, roots actually breath O2, which is integral to their growth and development. It is for this primary advantage that many commercial growers chose fabric grow bags, as the size of the root structure is directly proportional to the yield of the plant.
Grow bags do have some drawbacks.
Sometimes drainage is less than ideal and additional holes need to be made at the bottom of the bags to aid in drainage. Additionally, grow bags may not be as durable as pots, lacking the structural strength that other more solid containers can provide. This can be especially true in heavy rain outdoors or in heavy-flow hydro systems. The larger bags can also be much more difficult to move because of the lack of sturdiness and the weaker fabric handles are prone to tearing with bags over 20 gallons. (Note: Fabric grow bags come in a variety of sizes ranging from 1-gallon to 200+ gallon bags for outdoor use.)