Pot pourri is a mixture of dried flowers, herbs, grasses and pods. Just add a few drops of essential oil to the pot pourri – this way it will retain its aroma and you will feel a pleasant scent even after more than a month.
Another, even more effective way is to close the pot pourri after adding the oil, for example to a plastic box overnight, so that the oil is better absorbed into the contents. When you open the box in the morning, the room will be flooded with aroma, which will create a pleasant atmosphere for a long time.