Potting Soils for Raised Beds and Containers

Growing in containers and raised beds is a good option for many gardeners. Some of the benefits include less space required,  less weeding, quick setup, mobile pots and they can be placed on hard surfaces or hard ground. Besides, the box or pot that you will use to grow your vegetables in you will need some type of soil.  In my 40 plus years of growing plants in containers, there is one thing that holds true,  once you put soil into a container it behaves very differently than the soil that is is the ground. Mainly the drainage has to be much better in a container or the soil will hold too much water and the plants will suffer. The swings between wet and dry soil are more dramatic. Potting soil will either dry out too fast or stay wet too long depending on how well it drains and what it is made of.

Sometime back in the ’50s and 60’s nurserymen starting putting more plants in containers and they needed a soil mix that was light and drained well. The mix that was used was called a soilless mix because it contained no mineral or native soil. Instead, soilless media made from organic materials like peat moss, composted pine bark, perlite,  and vermiculite or other non-soil amendments. Today we can buy these potting soil mixes in a variety of recipes and brand names. I have always liked the peat moss based potting soils but I am beginning to try some mixes that substitute peat with coir. Coir is a ground coconut husk which is a renewable resource and is said to support microorganisms better than peat moss. Until I am more familiar with how to use the coir all my recommendations will be using peat moss.

The recipe I use now for growing vegetables works well in a pot or a raised bed like a square foot garden. Be sure your pot has drainage holes or you can use a self-watering container as I discussed in a previous post titled Self Watering Containers. The recipe I show below is one that I have used many times with good results. The amounts in this recipe are enough to fill a 4×4 square foot garden 8 inches deep. The brand names I use are what is available in my area and I am sure could be substituted as long as they are similar. Every cook will tweak a recipe to make it his own and I am no different with my soil recipe so this is not the only potting soil that will work but it is the one that has worked well for me. If you are growing in the ground using your native soil you may want to read my post titled What is Good Soil.

What is in Mike’s mix

* Sunshine #1 natural & organic potting soil. This potting soil contains 70 % Canadian Sphagnum Peat Moss, Coarse Perlite, Dolomitic Limestone, Organic Wetting Agent.  It is an OMRI listed soil and can be used in organic production. It comes in a loose-fill 2.8 cu footbag. This is a product sold by Sungro Horticultural in their professional line so you would need to get it from an independent garden center or greenhouse that could order it for you. We try to keep it on hand and sell it from our farm in Newnan Georgia. You can read about it online at Sungro.

Pro-Mix and Sungro are also brand names that work well

* Black Kow cow manure compost and Black Kow mushroom compost.  Black Kow is composted cow manure and Black Kow Mushroom Compost is composted chicken manure that was used to grow mushrooms then bagged and sold as mushroom compost. By using two different types of compost in your potting soil you will get a wider range of nutrients and minerals. You can read about it online at Black Kow

* Organic Fertilizer. We use organic composted chicken manure fertilizer 3-2-3 for most plants and feather meal 7-1-1 for the plants that use higher nitrogen.

* AZOMITE  is a rock powder that contains a wide assortment of minerals. The name stands for A to Z  Of Minerals In The Earth. We use these minerals every time we plant on the farm and in our potting soil. We sell this at our farm in Newnan Georgia or go online to find a dealer near you. Azomite

*Worm Castings. We starting using worm castings in our potting soil years ago and notice a big difference in plant growth and disease resistance. Worm castings are basically worm poop and it contains beneficial microorganisms for your plants. We don’t use as much as we do compost because of the price but think of it as a probiotic to inoculate the soil. Look for a local source, maybe someone that is growing worms for bait.  Some bags of worm castings have fillers of peat moss and are cheaper but you get what you pay for.  We have worm castings available here at Country Gardens Farm that we produce here on the farm.

Here are the amounts you will need to mix up approximately 10 cubic feet ( enough to fill a 4×4 bed that is 7 inches deep)

2  Bags of Sunshine Organic Potting Soil Each bag is 2.8 cubic feet

2 bags of black Kow Cow Manure Compost 40 pounds approx 1 cubic foot each

2 bags of Black Kow Mushroom Compost 40 pounds approx 1 cubic foot each

3 Pounds of Organic Fertilizer 3-2-3

1 pound of Azomite

4 Quarts of worm castings

The easiest way I have found to mix these ingredients together is to spread out a 10×10 tarp next to where you are going to use the soil. Thoroughly mix together all ingredients with a shovel and add just enough water to make the mix damp but not too wet. It can also be stored in a trash can for later use.