What does it take to keep a dandelion yellow for a long time after a fall?

The flower of the plant, being on the plant itself, receives nutrients all the time, therefore it lasts for a long time. If the flower is plucked, then, when the supply of nutrients and water stops, it will quickly fade. In order to keep it longer, it is necessary to provide food and water supply. To do this, it must be placed in a vessel with water. To keep it longer, you need to add nutrients, for example, a sugar cube, and so that harmful microorganisms do not multiply, an aspirin tablet.