Conoclinium spp.
mistflowers
Eastern and southern North America to Mexico
Overview
Conoclinium spp. is a small genus of about four perennial species in the daisy family (Asteraceae), native to eastern and southern North America and parts of Mexico. Once placed in Eupatorium spp., the genus is set apart by its flat-topped clusters of fluffy, disc-only flower heads in shades of blue, violet, and lavender. Plants grow 0.3-0.9 m (1-3 ft) tall and spread by rhizomes to form colonies 0.6-1.2 m (2-4 ft) wide or wider. The opposite leaves are triangular to heart-shaped, 3-8 cm (1.2-3 in) long, with coarsely toothed margins. Flowering runs from mid-summer into autumn, when the powder-blue heads draw butterflies, bees, and other pollinators. C. coelestinum is sold as blue mistflower or hardy ageratum. Stems are soft and may flop in rich soil or shade. The rhizomatous, self-seeding habit lets colonies spread quickly and crowd smaller neighbours, so the genus can become weedy in moist beds.
Native Range
Conoclinium spp. is native to North America, from the eastern and central United States south through Texas into Mexico, where it grows in moist meadows, stream banks, and open woodland edges.Suggested Uses
Grown in rain gardens, pond and stream margins, native meadows, and the moist parts of pollinator borders. The spreading habit suits naturalized plantings and informal masses rather than tidy edging. Plants are spaced 0.3-0.5 m (12-18 in) apart and fill in within a season.How to Identify
Appearance
Size & Dimensions
Height1' - 3'
Width/Spread2' - 4'
Reaches mature size in approximately 2 years
Bloom Information
Flowering begins in mid- to late summer and continues until frost, a span of 8-12 weeks in warm regions. The powder-blue heads open in flat clusters and are followed by small tufted seeds carried on the wind. Bloom is heaviest in full sun with steady moisture.
Detailed Descriptions
Flower Description
powder blue to violetFoliage Description
medium greenGrowing Conditions
Sun Requirements
Requires 4-8 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight
Care & Maintenance
Care Guide
Most species grow in full sun to part shade on moist, fertile soils and tolerate brief flooding along their native stream banks. They accept a range of soil types at a pH from slightly acidic to neutral, and growth is densest where the ground stays evenly moist. C. coelestinum is hardy in USDA zones 5-10 and dies back to the rhizomes over winter. Plants spread freely by rhizome and seed, so colonies expand each season and may need confinement in small beds. Pests are minor, though powdery mildew can appear on crowded foliage in late summer.Pruning
Stems can be cut back by half in early summer to reduce flopping and produce denser growth. Spent flowering stems are removed at ground level in late autumn or early spring. Lifting and dividing the rhizomes every few years holds the spread of established colonies in check.Pruning Schedule
J
F
M
A
M
J
J
A
S
O
N
D
summerfall
Container Growing
✓ Suitable for container growing
Minimum container size: 3 gallons