Blue Mistflower, Eupatorium Coelestinum for Late Summer and Early Fall Bloom

Ilona Erwin

An unfortunate mistake has lead to the writing of this plant profile. From a start my dad had given me, I had early-on grown Hardy Ageratum (AKA Blue Mistflower, recently officially labeled ‘Conoclinium coelestinum‘). It survived well in a poor area of the garden under a maple tree. Then, ensuing droughts and other onslaughts caused me to lose it, eventually.

Besides the sentimental sadness of losing a plant given to me by my father, the lovely soft blue blooms, so welcome in their timing, were sorely missed. Early September and the end of August is an otherwise scruffy time of the growing season. Fresh green leaves and soft sky blue flowers look so attractive and bright in the heat and amongst the often dry and battered foliage of the garden at that time.

I remedied this loss by buying (at what I deemed a premium price) some plants from an online source. Planted the tiny starts, and they eventually did well. This year they were promising to be at the height of mature glory.

Until the unfortunate event…

The Unfortunate Event 

ruined plant
Weed whacked and what’s left of a once thriving stand of Mistflower.

My family was lassoed into helping me when I could manage to convince them, but none had my love of plants and desire to know them, at that time. They did have their Dad’s love of mown lawns, cutting down things, and making the yard look neat with straight lines, and not too much nonsense. (How I think they perceive my enthusiastic gardens).

I convinced members of the family to help me with some of the more strenuous yardwork and had seen huge improvements because of their efforts. But then I found the Eupatorium coelestinum weed-whacked to the ground!  It was just coming into bloom. That is what I call an unfortunate event.

Years later, now, it has resumed its thriving status. A happy ending.

Plant Profile for Conoclinium coelestinum

blue mistflower
Conoclinium coelestrinum is commonly called mistflower or hardy ageratum. It is native to central and eastern USA.

I turned this bit of misfortune into a cause to rejoice. How you say? Besides inspiring an elegy to the Mistflower, the event became a renaissance of my Conoclinium coelestrinum‘s root parts into other areas of the garden.

How to Grow Hardy Ageratum

  • Light conditions of Full Sun to Full Shade. It was doing especially well in an area with full sun exposure to the east, with some protection from late afternoon sun.
  • Likes moisture, but also should have good drainage.
  • Hardy in Zones 5-11
  • Rich garden soil could be cause of too much of a good thing (Mistflower becomes a nuisance)

Propagation of Hardy Ageratum

  • Can be grown from seed easily, and may self-seed once established.
  • Propagate by root division
  • Softwood cuttings in springtime.

Uses For Blue Mistflower

As a late season bloomer, it can be mixed with asters, late season daisies, and anemones for a September garden show. Its spreading capabilities make it good for a groundcover, and it is used for erosion control on banks, etc. 

For Butterfly Gardens

Highly attractive to butterflies, hardy ageratum is ideal as part of a planting dedicated to the Lepidoptera. The blooms in color, contrast, and purpose would be perfect companions to Butterfly Bushes.

Butterfly Magnet

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Ilona Erwin, author

Meet the Author

Ilona Erwin

I started working on this website beginning in 1998, when it was part of Ilona's Reflecting Pool. Since then I've branched out into a number of online endeavors and work at writing lots of content for my sites. "Ilona's Garden" remains my primary site and is dedicated to home gardener's success.