Hardy Ageratum, Blue Mistflower

Conoclinium coelestinum

Family: Asteraceae (ass-ter-AY-see-ee) (Info)
Genus: Conoclinium (koh-no-KLY-nee-um) (Info)
Species: coelestinum (koh-el-ES-tee-num) (Info)
Synonym:Eupatorium coelestinum
View this plant in a garden



Water Requirements:

Average Water Needs; Water regularly; do not overwater

Sun Exposure:

Sun to Partial Shade



Foliage Color:

Unknown - Tell us


18-24 in. (45-60 cm)


18-24 in. (45-60 cm)


USDA Zone 5a: to -28.8 C (-20 F)

USDA Zone 5b: to -26.1 C (-15 F)

USDA Zone 6a: to -23.3 C (-10 F)

USDA Zone 6b: to -20.5 C (-5 F)

USDA Zone 7a: to -17.7 C (0 F)

USDA Zone 7b: to -14.9 C (5 F)

USDA Zone 8a: to -12.2 C (10 F)

USDA Zone 8b: to -9.4 C (15 F)

USDA Zone 9a: to -6.6 C (20 F)

USDA Zone 9b: to -3.8 C (25 F)

Where to Grow:

Unknown - Tell us



Bloom Color:


Bloom Characteristics:

Unknown - Tell us

Bloom Size:

Unknown - Tell us

Bloom Time:

Late Summer/Early Fall

Other details:

May be a noxious weed or invasive

Soil pH requirements:

5.6 to 6.0 (acidic)

6.1 to 6.5 (mildly acidic)

6.6 to 7.5 (neutral)

Patent Information:


Propagation Methods:

By dividing the rootball

From herbaceous stem cuttings

From softwood cuttings

From seed; direct sow outdoors in fall

From seed; winter sow in vented containers, coldframe or unheated greenhouse

From seed; stratify if sowing indoors

From seed; sow indoors before last frost

From seed; direct sow after last frost

By simple layering

By serpentine layering

By stooling or mound layering

Seed Collecting:

Unknown - Tell us


This plant has been said to grow in the following regions:

, (2 reports)

Auburn, Alabama

Morrilton, Arkansas

Pottsville, Arkansas

Elk Grove, California

Bokeelia, Florida

Fort Lauderdale, Florida

Jacksonville, Florida

Merritt Island, Florida

Miami, Florida

Oldsmar, Florida

Riverview, Florida

Calhoun, Georgia

Decatur, Georgia

Watkinsville, Georgia

Crescent City, Illinois

Itasca, Illinois

Mount Prospect, Illinois

Carmel, Indiana

Greenville, Indiana

Rochester, Indiana

Wichita, Kansas

Morehead, Kentucky

Taylorsville, Kentucky

Weeksbury, Kentucky

Abita Springs, Louisiana

New Orleans, Louisiana

Crofton, Maryland

Valley Lee, Maryland

Westminster, Maryland

Cambridge, Massachusetts

North Chelmsford, Massachusetts

Constantine, Michigan

Okemos, Michigan

Southfield, Michigan

Waynesboro, Mississippi

Grandview, Missouri

Hudson, New Hampshire

Frenchtown, New Jersey

Mount Laurel, New Jersey

Chapel Hill, North Carolina

Elizabeth City, North Carolina

Franklin, North Carolina

Greensboro, North Carolina

Raleigh, North Carolina

Winston Salem, North Carolina

Cincinnati, Ohio

Cleveland, Ohio

Glouster, Ohio

Grove City, Ohio

Reynoldsburg, Ohio

Muskogee, Oklahoma

Bethlehem, Pennsylvania

Lansdowne, Pennsylvania

Lititz, Pennsylvania

Newtown Square, Pennsylvania

Whitehall, Pennsylvania

Barrington, Rhode Island

Charleston, South Carolina

Conway, South Carolina

Florence, South Carolina

Saint Matthews, South Carolina

Clarksville, Tennessee

Nashville, Tennessee

Arlington, Texas

Austin, Texas (2 reports)

Carrollton, Texas

Cleburne, Texas

Crowley, Texas

Dripping Springs, Texas

Harlingen, Texas

Helotes, Texas

Irving, Texas

Longview, Texas

Meridian, Texas

Princeton, Texas

Rye, Texas

San Antonio, Texas

Alexandria, Virginia

Arlington, Virginia

Hood, Virginia

Leesburg, Virginia

Lexington, Virginia

Kalama, Washington

Milwaukee, Wisconsin

Westfield, Wisconsin

show all

Gardeners' Notes:


On Apr 21, 2016, wendymadre from Petersburg, VA wrote:

In my Zone 7A garden in Petersburg, Virginia, I first planted wild ageratum in a shady patch in the yard, with only sporadically amended soil. It didn't spread much, and I thought its blue blossoms would be pretty in other areas. When it got into a more fertile, sunny area, it spread vigorously. It was probably thirty inches tall, and crowded my roses. I decided to pull it out this year, and I found that its fat white roots had infiltrated the root mat of my woodland phlox. I pulled out the woodland phlox (in full bloom), tried to locate all the wild ageratum and eradicate it, and then replace the phlox. I don't know how much ageratum I missed. I like the flower, and I will try sinking it into the bed confined in three gallon pots. I also have other garden beds where I don't mind i... read more


On Nov 11, 2015, Sequoiadendron4 from Lititz, PA (Zone 6b) wrote:

Beautiful blue flowers grace this plant mid-late summer, which attract pollinators. It's quite hardy and easily moved to various locations often requiring little care. That's about all it has going for it as it is SUPER aggressive in the garden. It's aggressive to the point of getting tangled around other perennials making it nearly impossible to remove completely. I have removed much of ours this fall but still have a couple more spots to go. I don't even mind aggressive plants but this is one that will not continue to have a place in my gardens. Before the flowers open, the plant looks very weedy and has unattractive foliage. The seeds are plentiful but I haven't had a big problem with seedlings popping up all over. This plant would be perfect for an area that gets little attenti... read more


On Jul 30, 2015, Rickwebb from Downingtown, PA wrote:

This species is sold by both conventional and native plant nurseries. I only see it occasionally. It makes a good low garden perennial for late summer and early autumn bloom. It does spread quickly by underground stems and can easily invade outside of good boundaries and overcome other low plants.


On Apr 19, 2015, sladeofsky from Louisville, KY (Zone 6b) wrote:

Proper siting is everything. In the wild, I often see it barely hanging on, finding a niche here and there among stronger growing plants. However, it does spread rather quickly by its roots (it also reseeds.) I wouldn't call it "invasive" here, because it is a native doing what it's meant to do. I made a big mistake; I planted one as a taller accent in a small rock garden and it soon took over. Not a good neighbor to smaller plants. It is however perfect for growing amongst taller perennials such as Echinacea, Solidago (many bloom at the same time), and Rudbeckia (among many others, where it stitches together the design by growing around its larger neighbors. I still suggest growing it, but only where it can romp a bit without causing to much maintenance or heartache at losing rare, tiny, ... read more


On Oct 28, 2014, flowerman48jtdv from Southfield, MI wrote:

This is one of my favorite late summer to late fall hardy plants. I believe I bought a couple of clumps years ago at a garage sale here in Southeast Michigan near Detroit. This plant has come back reliably and it spreads. I relocated it from a border near my deck to a meadow I created in the back of my yard. The soil is very poor there and bone dry at times. This plant grows well and spreads but not rampantly. It's perfect for my meadow and it also tolerates shade! I just wish I could get more of it. I've never seen it at any garden centers. I feel lucky to have it in my garden.


On Apr 25, 2010, turektaylor from Elizabeth City, NC (Zone 8a) wrote:

WAYYYY too invasive, i'm still trying to pull all the underground roots !!!


On Oct 12, 2008, Meredith79 from Southeastern, NH (Zone 5b) wrote:

I grew this plant from seed in spring and they are blooming wonderfully right now. I used cold treatment and they germinated well. The resulting plants are in a spot that had full sun with a little shade later in the day - while the sun was high in the sky during early summer. Now that it is fall and the sun is lower they get part shade from nearby trees. I hope these are hardy here and reseed because in my opinion, you need a lot to have a nice show of blooms. If they aren't hardy for me I would grow them again as an annual. I've seen them being described as a moist site plant, but they've performed good enough for me with dryish sandy soil.
They need to be placed towards the front of a border, hopefully with a slightly lower growing and long blooming plant in front of them. Mine ... read more


On Sep 25, 2008, arthurb3 from Raleigh, NC (Zone 7b) wrote:

Blue mistflower ("Conoclinium coelestinum), the are great fillers that require no care but you want to place it in a confined area to keep it under control. It add valuable color to the Fall garden!


On Sep 11, 2008, MotherNature4 from Bartow, FL (Zone 9a) wrote:

These beautiful wildflowers are common in wet hammocks and pond margins throughout the state of Florida.


On Jul 26, 2008, quiltjean from North Chelmsford, MA (Zone 6b) wrote:

I got a bit of this from a friend because I love the color in late summer. I put it in a dappled-shade location and it has taken off. To prevent its smothering my precious primula I'm taking out a hunk to plant on our condo grounds. We have terrible soil--silty acid junk with awful drainage--so we try spreaders in shady areas where grass just won't grow.


On Aug 9, 2007, upsydaisy from Rochester, IN wrote:

I got a start of the hardy ageratum several years ago. It does well for me here in north-central Indiana, but I haven't had a problem with it being invasive, possibly because we are in zone 5. I really love it, and so do the butterflies!


On Mar 31, 2006, sterhill from Atlanta, GA (Zone 7b) wrote:

A friend of mine gave me this last summer and it bloomed big and beautiful. Now I am picking out millions of seedlings... and I find I can't just pluck out a little seedling but I have to dig down at least 4-6 inches as the roots go 'way down and I find a mass of white roots ready to spring up more seedlings. She has more shade and I don't think hers spreads like this. Mine are in full sun and are everywhere now!!!


On Oct 5, 2005, Breezymeadow from Culpeper, VA (Zone 7a) wrote:

This lovely plant grows wild on my property & throughout this area of Virginia (the Piedmont).

The fluffy little violet flowers are a wonderful accent in the late summer/early fall wildflower landscape, & the stem length makes it a nice addition to indoor bouquets.


On Oct 5, 2005, jnn from Pittsboro, NC (Zone 7b) wrote:

This is a beautiful fall-blooming plant that attracts butterflies and hummingbirds. It does have a tendancy to spread, but you can keep it in check. It is also easy to dig some up to give to friends or put in other parts of your garden.


On Dec 19, 2004, rcn48 from Lexington, VA (Zone 6a) wrote:

Lovely addition to the garden for its late summer/fall flowering. Although it can be invasive in some areas, we have ours planted in a border in non-amended soil and in 4 years it has not invaded its companions. Nice cut flower for fall arrangements.


On Aug 31, 2002, Terry from Murfreesboro, TN (Zone 7a) wrote:

I tend to like this plant because it is very carefree - it grows wild in a nearby cow pasture. However, it can be a thug, so watch that you don't plant it near something that has a delicate constitution. And don't feed or water it too much - thin, dry soil will help keep the growth in check.


On Aug 31, 2002, lupinelover from Grove City, OH (Zone 6a) wrote:

This plant is highly invasive in loose to medium soil. The beautiful flowers in late summer and autumn help to compensate for trait, though. Grows and flowers well in full sun to medium shade, wet to dry. A wonderful addition to a meadow or natural wildflower planting area large enough to accommodate a beautiful wildlife attractor.