Urtica dioica (stinging nettle) and Urtica urens (dwarf nettle) are members of the Urticaceae family native to Eurasia, and are considered therapeutically interchangeable.1 The term nettle is used in this article to refer simultaneously to stinging and dwarf nettle. Urtica prefers wet, rich soil and tends to grow in large patches. Stinging nettle is taller than dwarf nettle and is perennial; dwarf nettle is an annual. Both plants have fleshy, drooping, serrated, roughly heart-shaped leaves. The leaves and stems are covered with stinging hairs (dwarf nettle leaves are smooth and more delicate). Both produce inconspicuous green-white flowers in late spring or summer. The leaf, flower, seed, and root of nettle are used differently and contain different chemical constituents.