Ashwagandha, or winter cherry, is a non-toxic herbal shrub whose roots and berries are used for their medicinal properties. The herb is an important part of Ayurveda, the traditional system of medicine in India. It helps modulate stress and anxiety, increase energy level, and improve the immune system as it works to energize your nervous system. It is used to treat a range of conditions, such as rheumatism and insomnia.