The harmony between the plant kingdom and the human world is manifested in the fact that both are dependent on and complement each other. We see it at work, for example, in the most important of all vital functions: breathing. Human beings and animals inhale oxygen and breathe out carbon dioxide; plants take in carbon dioxide and give off oxygen. The well-known fact has far-reaching consequences from human life.

Today we know that plants contribute to the ionization of the air, mainly through the essential oils they release. In this context, the ionization of the air means the formation of the negatively charged oxygen molecules necessary for human life. The more ionized (negative ions) the air contains, the healthier and more vitalizing it is; the less ionized (positive ions), the greater the risk of susceptibility and poor health.

Various research studies have found evidence establishing that the aromatic compounds in plants have a constitution similar to that of the fluids in the tissue of the human body. This could explain the vivifying and harmonizing effect of aroma substances in plants. The relationship of our sense of smell with plants may be summed up as follows: smells we like benefit our health.

This harmony between plants and human beings is also expressed in other fields. Plants emit rays which have a positive effect on people. Each of us can verify this experience: we just have to think of the feeling of harmony and peace that we sense while walking in a forest, for example. The reverse is equally true. Our positive or negative attitudes towards plants can effect them in a positive or negative sense. No true gardener can deny that a plant looked after with care and love will grow to be stronger and more beautiful than the other. This also partly explains the mystery of "green thumb," or why some people's plants thrive so well compared to those of other people.

Try it for yourself: plant two seeds of the same plant in the earth. Water them alike, but pay more attention to one of them than the other by concentrating on it and talking to it. You will be astonished at the result. This interaction also explains why many amateur gardeners find gardening a relaxing, harmonizing and rejuvenating activity.