Blue mistflower (Conoclinium coelestinum) is a hardy North American native perennial that works well as a border plant or colonizing groundcover. Its fluffy, lavender-blue, ageratum-like flower clusters bloom from late summer until frost, attracting numerous butterflies and bees. It grows 1 to 3 feet tall, thrives in moist soil, and spreads quickly by rhizomes.

Quick Plant Facts

• Botanical Name: Conoclinium coelestinum (formerly Eupatorium coelestinum)

• Common Names: Wild Ageratum, Hardy Ageratum, Blue Boneset

• USDA Hardiness Zones: 5 - 10

• Height: 1 - 3 feet

• Spread: 1 - 2 feet (and spreading actively)

• Bloom Color: Blue, violet, or light purple

• Bloom Time: July through frost, typically October

Growing Conditions

• Sunlight: Full sun to partial shade; more sun yields heavier blooms.

• Soil Type: Highly adaptable to sand, loam, clay, or rich organic matter.

• Water Needs: Prefers consistently moist to wet soil. It is ideal for rain gardens and pond edges, though it tolerates brief dry spells once established.

Garden Uses & Wildlife Value

• Pollinator Magnet: Provides vital late-season nectar for monarchs, swallowtails, bees, and other beneficial insects.

• Naturalizing: Well suited to wild gardens, meadow-style borders, and damp ditches.

• Spreading Habit: Because it creeps via underground rhizomes and self-seeds, it forms a dense groundcover. It can be aggressive in small or formal spaces, so it is best used where it has room to roam.