Eupatorium coelestinum

Eupatorium coelestinum is a sturdy and tall herbaceous plant with pastel blue to lilac umbel-like flower heads.

It is a herbaceous perennial from the Asteraceae family, also known as Ageratum.  Native to North America, it has beautiful deciduous foliage in a deep green colour that turns lime-green during flowering. The leaves are oblanceolate. The plant bears its terminal flower heads in umbel-like clusters on sturdy wine-coloured stems, reaching a height of 80 cm (32in); giving it an upright and bushy habit. It commonly reaches a width of 60 cm (24in). The inflorescences can reach a diameter of 10 cm (4in), resembling bluish pompons with a slightly blurred appearance. It is true that the flowering period is a bit late, but it can embellish a garden throughout the summer until the end of October. It maintains its decorative aspect during winter thanks to its fruiting topped with small fluffy seed heads that disperse with the wind.

Eupatorium coelestinum is an easy-to-grow plant: it is resistant to insects and diseases. It is an extraordinary melliferous plant, attracting pollinators, especially butterflies. It is hardy and can withstand temperatures as low as -15°C (5°F). It is also a plant called an indicator species: in its natural state, it prefers to grow on fresh to moist soils, indicating a certain degree of soil moisture. You can plant it alongside a pond. It adapts to all types of soils, but it prefers moist, rich, and well-drained soils. They will look stunning in a wild garden as a groundcover on the edge of a flower bed, accompanied in the background by their larger relatives, Eupatorium cannabinum Plenum with double flowers. Prune the stems to maintain a more compact habit.

Eupatorium gets its name from the Persian emperor Mithridates Eupator, who boasted of surviving poison ingestion thanks to a powerful antidote. However, the knowledge of that time does not allow us to say with certainty whether the antidote in question was truly Eupatorium or Agrimony, two plants with strong similarities.