Which plant's root is used as a sedative and sleep aid?

The plant whose root is used as a traditional sedative and sleep aid is valerian. Products generally come from species in the genus Valeriana, especially Valeriana officinalis, and are prepared from the dried underground parts rather than the colorful flowers.

Valerian has a long history in European herbal medicine. Ancient Greek physician Hippocrates described its properties, and the Roman physician Galen later prescribed it for insomnia. The dried root contains volatile oils and compounds such as valerenic acid, valeric acid, and valepotriates, which are thought to influence nervous-system signaling, including pathways involving GABA.

Evidence for valerian is mixed: some reviews suggest it may improve sleep quality, while others find the results inconsistent or inconclusive. That uncertainty is why “traditional sleep aid” is more precise than calling it a proven cure for insomnia. Kava is another calming herb, but it comes from a different plant and has distinct safety concerns, while lavender and chamomile are usually used as flowers or aerial parts.