Eupatorium perfoliatum

Eupatorium perfoliatum is a robust perennial with creamy white corymbs and a slight vanilla scent. Belonging to the Asteraceae family, it is also known as American boneset, Indian ague weed, March sage, Wild sage, Feverwort or Thoroughwort.

Native to North America, it gets its name from the arrangement of its leaves on the stem, distinguishing it from other species of Eupatorium. The leaves are lanceolate, opposite, and sessile, meaning they are directly attached to the stem without a petiole.  They are deciduous, green-grey in colour, and pubescent on the lower surface. The plant bears its flower heads assembled in corymbs on robust, pubescent stems, reaching over 1 meter in height, giving it an upright and bushy habit. Smaller in stature than other species, it still reaches 40 cm (16in) in width. The corymb heads can reach 10 cm (4in) in diameter, resembling creamy pompons with a slightly fuzzy appearance.  Eupatorium perfoliatum flowers have a vanilla scent.

The late flowering adds charm to a garden throughout the summer until the end of October. It retains its decorative aspect in winter thanks to its seed heads which are topped with small fluffy crests that disperse with the wind. An easy plant to grow, it is resistant to insects and diseases. It is also an extraordinary pollinating plant, especially for bees and butterflies. Hardy, it can withstand temperatures down to -15°C (5°F). It is also a plant called a bio-indicator: in its natural state, it prefers to grow on damp or even wet terrain. It thus indicates a certain degree of soil moisture. It can be planted it by the edge of a pond. It adapts to all types of soil, but prefers moist, rich, and well-drained soils. It will be superb in a wild garden as a groundcover on the edge of a planting bed, accompanied in the background by the larger species,  Eupatorium cannabinum Plenum with double flowers. Prune the stems in autumn to maintain a very compact habit.

The name Eupatorium is derived from the Persian emperor Mithridates Eupator, who boasted of surviving poison ingestion thanks to a powerful antidote. However, it is hard to say with certainty whether the antidote in question was truly Eupatorium or Agrimonia, two plants with strong similarities.
More precisely, Eupatorium perfoliatum is used in Native American pharmacology.  Its various nicknames reflect the number of ailments the plant is reputed to cure  e,g, American boneset, as it is supposed to treat bone pain or Gravel root,  as it dislodges kidney stones. It has mainly been used for its medicinal properties to reduce fevers and fight infections, including malaria.  The list is not exhaustive. English speakers affectionately refer to all eupatoriums as Joe Pye Weed. One of the legends surrounding this nickname comes from the distortion of the name of an Indian doctor, who successfully treated people with typhus using Eupatorium perfoliatum. The plant is also widely used in homeopathy.