The best potting mix for growing woody plants in containers

If you are not using this potting mix for perennial or woody plants, they are probably less than happy. Most bagged product mixes on the market are meant for annual plants such as vegetables, tomatoes, herbs, and flowers that have very fine roots and only live for one season. If you are growing perennials or woody plants for longer than one season, you need to use a very different mix!

Here's Why This Mix Is Fantastic

Potting Soil Mixes Need To Provide Long Term Aeration (Which This One Does)

Air space in your soil, or lack of, is usually the number one reason a potted plant doesn't do well long term. A plant's roots need quite a bit of oxygen just like all other tissue, but unlike animals plants do not have a good vascular system for transporting it (i.e. blood). A plant's equivilant to blood is sap, which moves slowly and transports nutrients and water just fine but very little oxygen. Therefore the roots have to absorb all their oxygen from within the soil, and to do that they need the soil to have fairly good air circulation.

More air spaces in soil results in more oxygen being available to the root tissue, while less air space means less oxygen is available. But having air space alone isn't good enough, because soil that is not well drained enough will have those pockets filled with water instead of air. If those air pockets are frequently filled with water your plant will drown and this is what is commonly referred to as "overwatering your plant." Over time, two things will happen to those air spaces: First, as the structural components of your soil decompose the soil will compress and those air pockets will slowly get smaller. Second, your plant's roots are going to grow and expand and fill in those air pockets. With annual plants, this doesn't cause as much of a problem because the roots stay smaller and decay at the end of the year, plus many gardeners follow the general strategy of revitalizing their soil by churning it up a bit to restore the air spaces. But with long term plants, this process doesn't happen and the roots get thicker and more numerous every year and the soil breaks down and compresses. So you need a potting mix that will combat both issues.

Adding Shredded Bark Provides Ample Air Space And Breaks Down Slower Than Other Materials

Shredded bark breaks down very slowly and generally will keep its structure for several years. It also provides a significant amount of air space, so much that even agressive plant roots will take a long time to fill it all in. A good bark mix will provide around 30% air space with no large pockets. You can measure this by filling a container to the rim with bark and then pouring in water until it starts to overflow. Cover the top of the container with a mesh screen and pour out only the water into an equally sized container. The water that pours out should fill the second container about one third of the way up. This represents how much air space is held by the mix.