Conoclinium, commonly known as mistflowers, is a small genus of four species of herbaceous perennial flowering plants in the family Asteraceae (order Asterales). The genus is native to North America, with its range extending from Ontario and the eastern United States south to Florida and Texas, and westward through the American Southwest into Mexico and as far south as Guatemala.
Plants in this genus are upright, typically reaching 0.5 to 2 metres (1.6–6.6 ft) in height. They produce clusters of small, composite flower heads in shades of blue, purple, or violet — occasionally white — that give them their evocative common name. The foliage is opposite and toothed, and the plants spread readily, forming colonies in suitable conditions.
Conoclinium was long treated as part of the large, heterogeneous genus Eupatorium, but phylogenetic research in the late 20th century demonstrated that its species are more closely related to other members of the tribe Eupatorieae — particularly Ageratum — than to true Eupatorium. The genus was accordingly segregated and recognised in its own right.
The best-known member is Conoclinium coelestinum (blue mistflower), native to eastern and central North America and widely grown as a garden ornamental. It is also valued for habitat restoration, especially in moist or wet soils within its native range. Conoclinium dissectum (synonym C. greggii) occurs in the southern United States and northern Mexico, while C. betonicifolium ranges from Texas through Mexico to Guatemala.
Etymology
The generic name Conoclinium is derived from two Greek words: κῶνος (kônos), meaning “cone,” and κλινίον (klínion), meaning “little bed,” likely referring to the form of the receptacle or involucre of the flower head.
Distribution
The genus is native to North America. Conoclinium coelestinum has the broadest range, occurring from Ontario south through the eastern and central United States to Florida and Texas. Conoclinium dissectum is found in the American Southwest and adjacent Mexico (Arizona, New Mexico, Texas, and several Mexican states). Conoclinium betonicifolium extends through Texas and Mexico into Guatemala. One additional species, C. mayfieldii, is restricted to northern Mexico.
Ecology
Conoclinium coelestinum is particularly associated with moist habitats and is recommended for use in habitat restoration projects within its native range, especially in wet soils. The genus as a whole supports native pollinators, as the small composite flowers are accessible to a range of insects. Plants spread vegetatively and can form dense stands.
Cultivation
Conoclinium coelestinum (blue mistflower) is the most widely cultivated species. It is grown as a garden perennial for its late-season blue to violet flower heads, which attract butterflies and other pollinators. It tolerates a range of moist to average soils and performs well in partly shaded positions. Gardeners should be aware of its tendency to spread aggressively; regular division or containment is advisable. Within its native range it is also used in naturalistic plantings and ecological restoration.
Taxonomy Notes
Conoclinium species were historically placed in the large, broadly defined genus Eupatorium. Late 20th-century molecular and morphological studies of the tribe Eupatorieae (family Asteraceae) showed that they form a distinct lineage more closely allied to Ageratum than to core Eupatorium, leading to their recognition as a separate genus. Conoclinium dissectum retains the synonym C. greggii in some older literature.
