Question: the potting soil
Should the soil found in the pots be replaced every year to be able to plant flowers?
The soil: Answer: the potting soil
the soil we buy in the nursery is a mixture of various natural and non-natural products; in general it is peat, mixed with other types of earth, obtained from the decomposition of leaves, or from composting into different natural products; in addition to this there is added sand, or pumice stone, and even fertilizer; When this compound is used to fill the pots, the roots of the plants absorb mineral salts from the soil, which then, over time, tend to disappear from the growing medium. In addition to this, any mushrooms present on the plants tend to fall on the ground, where they can also survive the winter; the same applies to other types of parasites, such as larvae or pupae, which are coleoptera and lepidoptera. In the garden soil the same things happen, but in general the leaves of the trees also fall, which decompose enriching the earth with mineral salts; in addition to this, various animals feed on larvae and other insects, removing them from the ground, which is much less common in pots. So, after a whole year in the pot, the substance that we find in the pots is no longer the fertile soil we had bought, but it is certainly almost free of mineral salts, and very often contains many insects and various parasites. A plant buried in this compound certainly develops, but not in the best way, as well as being certainly an easy prey to a series of parasites, which are awaiting its arrival for months: in practice burying a geranium in the planter last year, you do not other than invite caterpillars and molds to a banquet.
Therefore, it is generally advisable to replace the soil in the pots every year, in this way you will have plants every year that will amaze your neighbors. However, if you choose a top quality soil: go to a nursery and ask for the best soil they have, avoid the one offered at the supermarket or discount store.
And the old soil?
If you have a composter, you can use it as an excellent composting material: after a few months in the composter the exhausted soil will be enriched with the lost mineral salts, and with the heat of the composter all the parasites will have died.