Agastache urticifolia aka Nettle Leaf Horsemint

Agastache urticifolia belongs to the mint family, Lamiaceae. It is a perennial, so it lives for years. Its common names include nettleleaf horsemint and nettle-leaved giant hyssop. It is native to southwestern Canada and the western United States. It grows in moist ground on open slopes and in canyons. It also grows in mountain valleys. These sites range from foothills to about 8,200 feet [2,500 metres]. It is not native to Britain or Ireland.

This tall plant grows in clumps and sheds its leaves each year. The RHS gives a garden height of 5–8 feet [1.5–2.5 metres]. Its shorter account gives a height of about 6.6 feet [2 metres]. Clumps spread about 1.6–3.3 feet [0.5–1 metre]. Plants take two to five years to reach full size. The stems are square, with green leaves in opposite pairs. The leaves have a slight sheen and a strong scent. They range from lance-shaped to triangular. Coarse teeth line their edges.

Small flowers grow close together in short, dense spikes. They may be pale pink, violet, or white. The plant blooms from mid to late summer. Its seeds are small nutlets that can be hard to handle. Its height suits flower beds and adds a strong upright form. The RHS suggests its use in cottage gardens. It also lists prairie planting and wildflower meadows. Both RHS and Plants For A Future support wildlife garden use.

Grow it in fertile soil that stays moist but drains well. It grows in full sun or light shade. It accepts chalk, loam, and sand. Soil can be acid, neutral, or alkaline. The RHS gives it a hardiness rating of H4. Plants For A Future lists USDA zones 7–10. Start plants from seed or divide clumps in spring. Cut off flower spikes once their blooms fade. Pests rarely cause harm, but powdery mildew can occur. Plants For A Future does not flag it as weedy.

Leaves, flowers, and seeds have food uses. Leaves and flowers give food a mint-like taste. Their coarse or gritty feel can make them less pleasing. Dried leaves and flowers also make herbal tea. You can eat the seeds raw or cooked. Their small size makes them slow to prepare. Plants For A Future records past leaf remedies for pain and other ailments. People took some leaf remedies by mouth. They also put mashed leaves on swellings. These records show past use, not proof that the remedies work. The same source lists no known hazards. That does not prove safety for every person or pet.