Conoclinium coelestinum 'Cori'

Common Name: mistflower 
Type: Herbaceous perennial
Family: Asteraceae
Zone: 5 to 9
Height: 1.50 to 3.00 feet
Spread: 1.50 to 2.50 feet
Bloom Time: September to October
Bloom Description: Blue
Sun: Full sun to part shade
Water: Medium to wet
Maintenance: Medium
Suggested Use: Naturalize
Flower: Showy
Attracts: Butterflies

Noteworthy Characteristics

Conoclinium coelestinum, commonly called mistflower, is a late summer to fall-blooming herbaceous perennial that is native to the Eastern United States. It looks like annual ageratum and in that regard is sometimes commonly called hardy ageratum. But it is perennial and can spread aggressively by rhizomes. It typically grows to 1-2’ tall on downy purplish stems clad with coarsely-toothed, ovate-deltoid leaves (to 3” long). The flowers of this member of the aster family lack rays. Numerous small, fluffy, tubular, blue-purple flowers (to 1/ 2” across) with discoid heads bloom from July to October in dense flat topped terminal clusters (corymbs). In Missouri, mistflower is primarily found south of the Missouri River in low wet woods, at bluff bases, and in moist ground along streams, ponds, sloughs and ditches (Steyermark). It is also commonly called blue boneset. Conoclinium coelestinum is synonymous with Eupatorium coelestinum.

Specific epithet means sky-blue or heavenly.

'Cori' is very similar to the species except the plants are more compact, the flowers are a lighter blue and the bloom period occurs slightly later. The cultivar name is varyingly spelled as ‘Con’, ‘Cory’ or ‘Corey’.


No serious insect or disease problems. Some susceptibility to powdery mildew. Leaf miners and aphids may also visit. Plants tend to flop and may need support. Spreading tendencies must be watched, particularly if planted in the perennial border.


Wild flower garden. Naturalized areas. Periphery of stream of pond. Open woodland garden. May be grown in borders as long as sited in an area where spreading roots will not interfere with other plants.