In a previous article I recommended raised beds as one of the preferred methods of gardening. In this article I want to go into growing mediums for your garden.

First I want to explain the three basic components to the process required for plants to grow. They are photosynthesis, respiration and transpiration.

Photosynthesis is the process of capturing light energy and converting it into sugar energy, in the presence of chlorophyll using carbon dioxide (CO2) and water (H2O).

Respiration is the process of metabolizing sugars for energy to grow, reproduce and perform other life processes.
Transpiration is a process whereby a plant gives up water vapor through the stomata of their leaves.. As a plant transpires it pulls up water and nutrients from the growing medium which in this case is your soil but it could just as easily be a hydroponic liquid.

That explanation justifies the reason why you want to have the best growing medium possible in order to produce the best plants possible.

Let’s take a segue into calculating the amount of growing medium need for a raised bed. Although this is a nobrainer for some it’s a challenge for others so I thought it would be worth explaining here.

This is the basic formula Length x Width x Height = total cubic feet of growing medium. Each dimension must use the same unit of measure or you won’t get the correct answer. In this case we are going to use feet. So before you can multiply everything together you must convert the height of your raised bed from inches to feet.

For example if you will be using 10 inch lumber or stone, the formula is inches divided by 12 equals feet. In this case 8 inches / 12 inches = .83 feet rounded off.

Let’s say that your raised bed will be 4 feet wide by 8 feet long. The total amount of growing medium needed would be 4 feet x 8 feet x .83 feet = 26.56 cubic feet.

If you are going to buy soil in bags it’s an easy process to divide 26.56 by the cubic feet per bag to get the total number of bags needed to fill the bed. If you are buying a bulk deliver of soil or compost you will need to think in terms of (cubic) yards. A cubic yard is 3 feet x 3 feet x 3 feet = 27 cubic feet. In the calculation above you only need 26.56 cubic feet. That’s less than 1 cubic yard.

The formula for converting cubic feet to cubic yards is cubic feet divided by 27 (cubic ft/yd).

Raised Bed Volume CalculationWith that out of the way, back to quality growing mediums. All plants require an assortment of basic nutrients to grow and thrive. Purchasing a known quality growing medium is the only way to be assured that you will have sufficient nutrients for your garden.

Get the best that you can afford. If you are buying bags of product, read the analysis of the ingredients in the bag. Along with the major nutrients N (nitrogen) P (Phosphorous) and K (potassium) you also need a blend of micro nutrients like Calcium, Magnesium, Boron, Copper, Chloride, Iron, Manganese, Molybdenum and Zinc.

Mushroom CompostYou can skip the bag reading process altogether and just get mushroom compost. It’s also possible to get it delivered in bulk depending on where you live.

The alternative to buying bags would be to supplement your growing medium with the needed ingredients.

You could get a soil test and supplement the deficiencies or you could just purchase a complete blended supplement. Check out the Mittleider nutrient formula from Amazon or you can check out the Mittleider weekly feed here.