Horse balm is a large leafy woodland member of the mint family. It spreads only slightly by underground roots which form small tubers that are extremely hard giving rise to another common name for the plant: stone-root. The plant is very upright growing with several large leaves at the top of the stalk from which a spike of yellowish flowers emerge in the summer from July to September. Preference is for full to part shade and rich woodsy soil often in areas abounding with limestone. 2-4 feet tall. zone 4-8. VA ecotype.