Garden soil can be used as the base of a homemade potting mix, but it is never ideal. This is because it has more unknowns and weed seeds than commercially available potting mixes, which is not desirable for either an indoor or outdoor container. Using any potting mix will ensure that you have the right balance of aeration, drainage, moisture retention and nutrition.
Plants need good drainage, to prevent root rot. The ideal potting medium for containerized plants has a very open texture. This allows good aeration for the roots and prevents the soil from becoming waterlogged. Soil in containers can become waterlogged because it expands when it absorbs water, but cannot easily shed it. So, the plant's roots sit in an environment where the air is already saturated with water, and this causes plant diseases. Garden soil often is not very open structured and will not allow good aeration or drain freely.
Garden soil is actually a very poor choice of potting mix because of its low nutrition, especially for houseplants. If you use this type of soil in a container, you will see your plants grow smaller and less healthy than they should be. In fact, houseplants grown in pots with garden soil are often more susceptible to disease.
The organic matter and nitrogen levels in garden soil are not high enough to promote good plant growth. Over time, this can lead to nutrient imbalances in the soil resulting from the lack of proper balance. These imbalances can also lead to root rot and fungus problems if left unchecked. Even plants that do well under poor conditions can become weaker when grown with this type of soil.
Potting mix has this all figured out already - it has been treated with composting agents, such as peat, bone meal and has loads of organic matter. These are all very good fertilizers for many plants. You can add these to the resultant mix to suit your needs and types of plants. When you use commercial potting mix in pots, then the nutrients are mixed in properly.
You can create potting soil with garden soil by mixing in commercial potting mix and other fertilizers according to your needs. The proper balance is important, so you should add the right amount of each to your garden soil for the best results. You can also create a soil booster by adding ground up egg shells, coffee grounds or peat moss to your garden soil.
You can buy bags of prepared commercial potting mixes online or at garden centres. Make sure you read the instructions on the bag before starting. If you choose wisely you should be able to get good results every time.