What Soil Should I Use In My Raised Garden Bed?

Written by Brian Smith
So you’ve made the decision to purchase one or more Cedar Planters, to begin growing vegetables, herbs, or beautiful flowers! You're ready to enhance your patio, veranda, deck, or balcony. The next step is to fill them with soil to grow your plants ... but the question is

“What kind of soil should I use?" 

If you think that all soil is the same then think again. My alma mater, The University of Guelph (Go Gryphons) has an entire department dedicated to Soil Sciences. Here is what you need to know about the different types of soil you can use in your Cedar Planters (and which choice I'll be making for mine)! 
It is important to know that soil from your existing gardens is probably not a good option. It likely contains weeds which will drive you crazy, trying to continually remove these from your planters. Secondly, if you live in an area where the soil is basically clay, like myself in Hamilton, ON, you’ll end up with a big, giant brick in your Cedar Planter ... and nothing will grow in that!
Let’s look at three other options you can use and which option I found to be best in my Cedar Planters.The soils available to you are Potting soil, Triple Mix and Black Garden soil.


Potting soil is actually not soil at all. It’s a composition of compost, sphagnum moss, vermiculite, perlite, and sometimes coir which is coconut husks. After a short period of time the compost is depleted and the other components have no nutrients in them as they do not retain nutrients well. Thus you will constantly have to fertilize your planters with commercially made fertilizers, which I refrain from doing as I am an organic grower. It’s very expensive to fill a Cedar Planter with and doesn’t have enough nutrients to feed plants season after season. We’ve used this in the past with our hanging pots, but after one season, the planter soil is so dried up it turns into a clump of dust that can’t be used anymore. The only time I will use potting soil, is to start my seeds indoors in March, that I will then plant in my Cedar Planters in mid May. The conclusion here is avoid potting soil like the plague (and Covid) for use in your cedar planters!  


Triple Mix as the name explains, is comprised of 1/3 soil, 1/3  peat moss, and 1/3 compost or composted manure. You can gets this either in bags at your local gardening centre, or in bulk at a landscape centre and then have it delivered to your home. This is a much less expensive option, if you have multiple planters to plant. This is a good growing medium for your plants but does have one big draw back: after a period of time the peat moss and the compost/manure will become depleted, break down and low and behold (no pun intended), the soil in planters and raised beds will actually have sunk. This mean you now have to top up your planters, usually every year to bring them back to a normal level.
I consulted with my son-in-law who is a landscaper and he told me he only uses triple mix to enhance a garden bed, especially one that has a lot of clay in it as both the peat moss and manure will help to break down the clay for better soil for growing plants in. He also doesn’t recommend it for the Cedar Planters for the above reasons.


My choice for my Cedar Planters is black soil, which again can be purchased in bags at your local garden centre or in bulk at a landscaping centre. This type of soil has plenty of nutrients for your plants and a bevy of microorganisms to help break down these nutrients for the plants to absorb. To enhance this soil, I also combine this with composed mature for the perfect growing environment. Before you start adding composted manure, sheep or cow, please read my blog on manure as it will depend on what you plan to grow as to what type of manure to use. 


Right now as I look out my window writing this, snow is falling (I hate winter) and I’m already starting to plan my gardening for this year. Seeds have been purchased, and indoor planting will begin in March ... so watch for my next blog on “Starting Your Gardens From Seeds Indoors”. This will come after my wife and I return from our Caribbean vacation to get away from this Canadian winter and look forward to spring and summer! 

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