Potting/Nursery Soil Rant

Potting soil is not good for bonsai. A flower requires a good growing medium which will be thrown out in three months. Ta da, we have potting soil. It is a mix of sand and peat with a bit of fertilizer. Peat is dead moss. Roots find it easy to grow in this mixed medium, especially the freshly transplanted flowers. As moss is an organic compound and it has no cellulose structure it breaks apart over about 8 months. It breaks apart because of swelling and drying out, as well as through natural decay processes. The broken bits filter in between the sand and plug up the spaces. Water no longer flows through the soil watering the roots of the plant in it. Water pools on the top and seeps down the insides of the pot. What little water does make it inside the tight packed soil mass does not evaporate quickly and promotes rotting of the root. Of course rotting roots are bad, so potting soil is therefore bad too.
Nursery soil is about the same but the soil mixture includes a substantial portion of bark. Too much bark promotes too much moisture. As well, the high proportion of bark means a lot of organic material is breaking down at the same time. The bark is composed of cellulose, it has a harder structure which takes about 1 year to become compacted.
The solution to a plant in a compacted soil is to transplant the tree when the tree is healthy and vigorous. If it is not the right time for transplanting, the plant's soil should be fully immersed in water occasionally. Keep the plant's soil underwater until it stops bubbling.