Echinacea purpurea
Very popular medicinal plant for strengthening the immune system.
Echinacea needs between 5 and 10 hours of direct sunlight per day, so it should always be grown outdoors in a well-sunny spot. Water it moderately, allowing the soil to dry out slightly between waterings, as it does not tolerate excess moisture. It is a very hardy plant with strong frost resistance, so it survives without winter protection in most climates. Plant it in autumn or spring in well-drained soil and enjoy its purple flowers throughout the summer.