Arnica cordifolia aka Heart Leaf Arnica

Arnica cordifolia is also called heartleaf arnica. It belongs to Asteraceae, the daisy family. This North American plant is a perennial. Its native range starts in the subarctic. It extends into the western and west-central United States. Records cover much of western Canada. They also include several provinces in central Canada. In the United States, it grows south to Arizona and New Mexico. It grows in woods, from foothills to high mountain sites. It is not native to Britain or Ireland.

Plants grow about 1.6 feet [0.5 metres] tall. They live for more than one growing season. They come back each year. The supplied species account says they bloom in July. Each flower has both male and female organs. Insects move pollen from flower to flower. The evidence gives no leaf shape or fruit details for this species. It gives no measured spread for plants grown in gardens.

An edge of a woodland garden suits this plant. It can grow in sun or light shade in woods. It prefers moist soil with good drainage and much humus. Sand, loam and clay all suit it. The notes also list a mix of sand, loam and peat. Soil can be slightly acid to neutral. The growing notes favour soil with no lime. PFAF lists it as hardy to UK zone 2. This is not a rating on the RHS H-scale.

Grow new plants from seed or divide them in spring. Sow seed in a cold frame in early spring. Cover it with just a thin layer of compost. Do not let the compost dry as seedlings grow. Move each seedling to its own pot when large enough to handle. Keep young plants under glass for their first winter. Plant them out in late spring or early summer. The evidence names no specific pests or diseases.

The supplied account records no food use for heartleaf arnica. PFAF warns that all parts are poisonous. Records describe its use on bruises, sprains and swelling. These uses involve treatments put on the outside of the body. For these treatments, the records favour flowers over roots. They describe past uses, not proof that treatment is safe. The safety note restricts use to unbroken skin. Records also list its use as a hair conditioner. They give no details on how to prepare it.