Valeriana officinalis is a medical herb that has been associated with helping with sleeping disorders and anxiety since the times of ancient Greece.
WebMD has a decent, research-based overview regarding Valerian. At the risk of editorializing, it is difficult to fund modern, peer-reviewed research on herbs that grow like weeds and cannot be patented.
This herb is so potent that even the fragrance has been documented as calming and helping with sleep.
Unlike many medicinal herbs, Valerian can be a rampant grower. There are few herbs that can compete hammer-and-tongs with nettles but valerian is one of them.
Plants are widely available and can be found at many nurseries including locally at Umbel Nursery in Parma, Michigan.