Playing in the Dirt: Choosing Soil for Container Gardens

Soil is the most important component in gardening and it is even more so in container gardening. In my opinion, the whole point of container gardening is great results, huge plants and constant blooming. The best way to achieve this is to use the best soil possible. Soil can make or break a container. In some instances, rich soil will be a detriment (i.e. morning glory, moonflower and other vines in the ipomoea family) but for the most part, good soil is a must.

I don’t really recommend filling your pots with soil from the garden for several reasons. One, you don’t really know what the content of that soil is and just how well your plants might do. And again, the whole point of container gardening is good results. Second, the soil tends to be heavier (particularly here) and less rich. Perennials may do well but for short term growth? Not so much. In order to get this soil up to snuff you would have to add things like peat, perlite, and fertilizer and you still won’t be able to predict results. There’s also the possibility of having a high salt content, high or low ph or toxins in the soil that will affect plant growth.

I really recommend using potting soil that you either buy of make yourself. In our region Minnesota, peat based potting mixes work best with our water conditions. I have used Miracle Gro soil (which is a bark based soil) with satisfactory results so I can’t discount that entirely. Whichever you choose, I do recommend a potting mix with time release fertilizer mixed in the soil. If you can get a mix with the water saving crystals, I say get it. There have been some studies that say these crystals don’t significantly reduce watering. And I would say that likely true but I think what it does do is reduce stress on your plants in the hotter weather. You will still have to water everyday but the plants won’t dry out as bad between waterings. If it buys you a couple of hours until you get home from work and your plants aren’t stressed and wilting, I think it’s totally worth it.

If you have a lot of large pots or the cost of the premixed potting soil is cost prohibitive you can mix up your own soil. Buy the very basic potting soil for a couple of dollars per 20 pounds. In this area it’s sold under the name Hyponex. It does come with perlite added so you won’t have to add that, but you will have to add peat. Peat is fairly cheap and one of the best things you can do for any soil. As is the way I do things, I don’t have an exact ratio of soil to peat. I would do about half and half or at least enough peat to give the soil a more brown color and a lighter texture. Also, you will need to add Osmocote, a time release fertilizer. Follow the directions on the package. Mix up all the ingredients in a wheelbarrow or other large container. You can also add the water crystals if you desire.

I also recommend using new soil in your containers each year. The soil will be largely depleted after a season of use and the effort to get it back up to snuff, in my opinion, just isn’t worth it. In very large pots, I don’t dump all the dirt but probably about the top third or at least what it compacted with old roots. I dump all the old dirt in my garden. I figure if it has any magic left in it, it can help my perennials.

Choosing the right soil will vastly improve your container results. It’s the foundations of gardening. Get this part right and everything else is practically effortless.