Many gardeners are confusing about the choice for the soil for their favorite indoor plants. Actually, the main functionalities of the potting soil are to support the plant in the container and provide adequate nutrients and water for the root of the plant. Also, the soil will be responsible for the air circulation for the roots as well.
Currently there is a variety of potting mixes products for sale in all gardening stores. Although it looks like soil, it is actually a mix of some base components such as peat moss with some types of organic matters such as barks adjusted together. These organic components are capable of improving the drain ability and the air circulation. The main ingredient of most commercial potting mix is the peat moss which is actually some deposited plant remaining. The shape of the potting mix is coarse power which is used for keeping the water. This ability is very useful for some plants which prefer a moist environment. Apart from some water-retention components, the indoor plant soil mixes also includes fertilizer to provide nutrients to the plants.
Although the peat moss based potting soil is good for the growth for most indoor plants, the fast growth will slow down after some time. This is because those soil mixes are not designed for the long term growth for the plants. So, after the first couple of weeks, the growth of the plants will slow down. The reason is because of the decomposition of the peat moss is very quick and so is the organic matter. The breaking down of these components will cause a number of bad things. The drain ability and air circulation is caused poorly because of the size of the particles is turning smaller when the organic matters are decomposed. This will cause some undesired objects such as salts accumulated in the roots of the plant, which will result in serious damages on the plants' roots.
The solution for the above problem is to change indoor plants soil mix every year to remove the old decomposed ones. Also, some elements such as perlite can be added to the soil mix to slow the decomposing process. You can also make your own soil for household use by using some long-term components like bark and vermiculite. It is believed that some homemade soil mix can last a longer period than the expensive commercial ones from the market.