Raised garden beds are used today to avoid vegetables and other plants from growing in soil that contains potentially harmful contaminants. These garden beds are raised boxes where the only soil contained in them, is the soil which you place there and so is clean and free from dangerous contaminants. Obviously the soil that you add will not contain vital nutrients needed for healthy growth and so you will also have to add those and as the soil in these types of beds seems to dry up faster than in ground soil, they will need to be watered more frequently. Unlike garden planters these beds have no bottom and so later, when the plants have grown and have become stronger, less susceptible to harmful contaminants; they can spread their roots into the ground soil where they will benefit from the natural nutrients that it possesses.
Although people do make their own raised garden beds from wood, most people prefer to buy plastic garden beds. If you opt to make your own from wood, it is advisable to use a cedar as that has its own protection from rotting and so will last much longer than most other woods. The size of the beds is personal choice, including how deep you make them. If you buy a bed, it will be available in a variety of depths ranging from 6 inches to 36 inches but the most commonly used is one that is 11 inches in depth. Usually 11 inches allows adequate soil for the healthy growing of your vegetables but some people prefer to have deeper ones as they can sit on their side and make it easier for carrying out different tasks like weeding.
As our planet continues to become increasing more contaminated with an assortment of toxic and other potential harmful contaminants, the quality of the soil also becomes increasingly contaminated and so an ever increasing number of people are resorting to the use of raised garden beds to ensure that the vegetables that they grow are healthy and good to eat. Even if currently, your soil in the area where you live is contaminant free, there is no telling how long it will stay that way and so if you have any concerns at all, you should perhaps consider making or buying a raised garden bed. There are of course disadvantages to raised garden beds but as these are limited to having to water more frequently and having to pay for the soil you use, the advantages far outweigh them. Some people, even though they live in an area where the soil is good, choose to use raised garden beds as they can add character to a garden and yet require little extra work. Once a raised garden bed has been placed in position and it is placed correctly, it can remain there for a long time, especially if it is made from plastic.
As contamination is the biggest concern for people that buy these raised garden beds, the manufacturers do not add to the problem; they use recycled plastic.