Arnica montana aka European Arnica

Arnica montana is a perennial herb in the daisy family. Common names include mountain arnica, mountain tobacco, and leopard's bane. It comes from Europe, including central and northern regions. It is not native to Britain or Ireland. Wild plants grow in mountain grasslands, pastures, and open woods. They also occur in meadows, scrub, and dry pine woods. Many sites have poor, acid soil.

The plant forms an upright clump with a basal leaf rosette. Garden plants reach about 1.6 feet [0.5 m] tall and wide. One source gives heights up to 2 feet [0.6 m]. The green leaves fall away at the season's end. Broad, oval basal leaves reach 0.5 feet [0.15 m] long. Simple stem leaves grow in opposite pairs. Their edges have teeth, and veins run along their length. Fine hairs cover the upper leaf surface and upright stems. Each stem carries one flower head at its tip.

Yellow to orange-yellow rays surround a centre of yellow disc florets. Flower heads span about 0.16–0.26 feet [0.05–0.08 m]. North Carolina State lists flowering from May through August. Chicago Botanic Garden reports September to October, so timing varies. Bees, flies, moths, and butterflies visit the blooms. Achenes follow the flowers, with a tuft of yellow hairs. The bright heads suit borders, rock gardens, and meadow plantings. They also fit cottage gardens and beds for pollinators.

Grow arnica in sun, with moist soil that drains well. It also tolerates some shade. RHS recommends soil rich in humus. Sources list a broad range of soil textures and pH. Growth is moderate, and plants take two to five years to mature. RHS rates it H6 for winter hardiness. Published USDA ranges cover zones 4–8 or 4–9. Wind may make the stems need support. Cut stems down after flowering, and divide clumps every few years. Roots can spread beyond the space set aside for them. Slugs and caterpillars may cause damage, though serious disease is uncommon.

Arnica is not edible, and the whole plant is toxic. Eating it can cause vomiting, heart problems, and breathing trouble. Large amounts can be fatal. Contact can also cause a skin rash; wear gloves when handling it. Dried flower heads have a long history of herbal use. External preparations have been used for bruises and sprains. This history does not make the plant safe to eat. Collection for medicine has helped threaten wild populations in some places.