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PlantFiles: Floss Flower, Ageratum
Ageratum houstonianum

Family: Asteraceae (ass-ter-AY-see-ee) (Info)
Genus: Ageratum (ad-jur-RAY-tum) (Info)
Species: houstonianum (hoos-toh-nee-AH-num) (Info)

12 members have or want this plant for trade.

View this plant in a garden


6-12 in. (15-30 cm)

9-12 in. (22-30 cm)

Not Applicable

Sun Exposure:
Full Sun

Seed is poisonous if ingested
Parts of plant are poisonous if ingested
All parts of plant are poisonous if ingested
Handling plant may cause skin irritation or allergic reaction
Plant has spines or sharp edges; use extreme caution when handling
Pollen may cause allergic reaction

Bloom Color:
Pale Pink
White/Near White

Bloom Time:
Late Summer/Early Fall
Mid Fall
Late Fall/Early Winter


Other details:
This plant is attractive to bees, butterflies and/or birds
Flowers are fragrant
Average Water Needs; Water regularly; do not overwater
Self-sows freely; deadhead if you do not want volunteer seedlings next season

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:
From seed; sow indoors before last frost

Seed Collecting:
Allow seedheads to dry on plants; remove and collect seeds

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There are a total of 17 photos.
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6 positives
4 neutrals
2 negatives

Gardeners' Notes:

Positive cathy4 On Mar 16, 2011, cathy4 from St. Louis County, MO (Zone 5a) wrote:

Mine returns year after year in the same spot, it has morning sun and blooms nicely in fall. It has not been aggressive and is easy to pull any stray plants.

Positive blondhavmofun On Mar 30, 2009, blondhavmofun from Orlando, FL wrote:

it may be invasive and has spread all over i love it because the butterflies love this plant. wish to keep it going. if you dont like invasive you definitely wont want this one.

Negative BotanicalBoi On Feb 8, 2008, BotanicalBoi from Carrollton, GA (Zone 7b) wrote:

This plant is a terror when it comes to staying where you want it. A neighbor 3 houses down from me planted it and the next year I had a yard full of it. I have been trying to kill it off for a few years now. More like a weed to me. Cant see why anyone would want this in their garden by choice.

Neutral midwestmama On Nov 23, 2007, midwestmama from Saint Charles, MO (Zone 5b) wrote:

While I have purchased this plant for borders in my garden at home (zip code 63301 - Zone 6a) and it has grown well with no problems of invasiveness, I had never found it growing in the wild before. We found this plant growing wild on our property next to the river (zip code 63625 - Zone 6b). It was growing both in the shade and in a partially sunny area. The areas were fairly wet with rich soil, and the plants seemed to be approximately six inches in height, good blooms, and good leaves. I will be anxiously waiting to see if they come up again next year.

Negative hymenocallis On Oct 2, 2007, hymenocallis from Auburn, AL (Zone 8a) wrote:

Sometimes people confuse Eupatorium coelostinum (mistflower) with this plant. I suspect it developed from it. E coelostinum is defintely beatiful but a bear to deal with in a flowerbed with other plants. Extemely invasive with extensive white rhizomes.
For those who found it growing in their yards it is probably this plant as oppsed to A. houstonianum. Both reseed everywhere. I let one grow for a year because my wife liked it and that was 5 years ago and I'm not rid of it yet and I suspect I never will be.

Neutral DreamOfSpring On Nov 27, 2005, DreamOfSpring from Charleston, SC (Zone 9a) wrote:

I kept finding these cute fluffy little blue flowers popping up in various nooks and crannies around the yard, not in actual flower beds. Thought they were "weeds", even pulled a few, but kept finding myself attracted to the flowers. Don't know where they came from. I did sow some wildflower mixes last spring. This plant is not on the list, but may be one of those listed on the package as "others". Anyhow, considering that they are growing in uncultivated soil and apparently as a result of seeds broadcast elsewhere and washed about by rain, they must be pretty easy to grow from seed.

Positive JaxFlaGardener On May 7, 2005, JaxFlaGardener from Jacksonville, FL (Zone 8b) wrote:

This plant was growing in semi-shade in one area of my yard when I bought my house three years ago. I assumed it was a wildflower, but I can't find any reference to Ageratums in my field guides, so it may be a remainder from some previous gardener at my property or a self-seeded stray.

I greatly enjoyed the blue tufts of flowers in Autumn when most other plants had ceased blooming. My A. houstonianums are most similar to the first photo in the pixs for this plant on this page, except that they are closer to a "true" blue, which seems to be a color hard to find in plants.

I made a decision to devote the area completely to liriope where the Ageratum was growing. I enjoyed the plant so much that I decided to move it to some other locations and provide it with more sun. That was somewhat of a mistake. It responded to my kindness by multiplying 1,000 fold! It was nice to have a huge patch of blue in my blue/white garden last Fall, but it reseeded and also spread by its shallow underground root system to cover much of that garden plot as well as much of the other area where I moved it.

IF YOU WANT THIS PLANT, just let me know you are willing to pay postage and I will send you a bare root BOX full of it! I need to pull up most of it before it spreads further, but I hate to destroy it as it is so attractive when in bloom. It seems to survive bare root transplanting without much stress. I am sure I will have plenty of new seedlings each Spring for years to come.

Positive melody On Jan 3, 2005, melody from Benton, KY (Zone 7a) wrote:

A welcome sight every autumn...the fields have a cheerful look with these beautiful little flowers.

Cattle won't graze them, so they dot the landscape each fall.

Spreads by underground runners and by seeds...easy and carefree, few pests. A great plant for a natural garden

Positive OldFlowerGirl On Aug 31, 2004, OldFlowerGirl from Castlegar, BC (Zone 6b) wrote:

I live in the Southern Interior of British Columbia and found the the Hawaii Shell Pink Agertum plants that I grew in a South exposure flower bed did extremely well. Grew quickly into lovely bushy plants with lots of purple/pink blooms.

Positive julie88 On Aug 16, 2004, julie88 from Muscoda, WI (Zone 4b) wrote:

My experience with Ageratum has been very positive. This year I've used several plants in my window boxes and have been extremely pleased with their color and behavior. I've also learned that they are easily rooted by pinning a longish stem to the soil next to the parent plant. In a couple of weeks, I had a plant that was ready to be separated and potted in a new location.

My next experiment is to see if I can keep a few of my plants alive, since this variety is not available every year. Right now I'm planning on keeping it in a windowsill until I have a lighted system for my plants.

Neutral CanadaGoose On May 17, 2003, CanadaGoose from Oakville, ON (Zone 5b) wrote:

Self seeded agerata may be considerably taller than store purchased plants. 24" or more

Neutral smiln32 On Aug 30, 2001, smiln32 from Oklahoma City, OK (Zone 7a) wrote:

Half-Hardy Annual. Fluffy flower clusters bloom all summer on these compact plants. Don't cover your seeds; they need light to germinate. Floss Flower is an effective selection for your border or as an edging. The soft blue flowers are an excellent accent for other flowering border plants or foliage plants. They will benefit from a monthly fertilizing. Deadhead faded blooms to encourage new flowering. Start seeds indoors at 70-75 degrees F and set out your transplants after all danger of frost. May be grown in partial shade; this is recommended for hot climates. 'Blue Blazer' and 'Blue Mink' are two tried and true varieties.


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

Auburn, Alabama
Garberville, California
Merced, California
Palm Springs, California
Greenwich, Connecticut
Bartow, Florida
Hollywood, Florida
Jacksonville, Florida
Keystone Heights, Florida
Lake City, Florida
Orlando, Florida
Athens, Georgia
Atlanta, Georgia
Carrollton, Georgia
Monroe, Georgia
Hampton, Illinois
Benton, Kentucky
Ewing, Kentucky
Hanson, Kentucky
New Orleans, Louisiana
Beverly, Massachusetts
Mason, Michigan
Waynesboro, Mississippi
Black, Missouri
Bridgeton, Missouri
Saint Charles, Missouri
Saint Peters, Missouri
Roselle, New Jersey
West Islip, New York
Charlotte, North Carolina
Raleigh, North Carolina
Glouster, Ohio
Coos Bay, Oregon
Schwenksville, Pennsylvania
Charleston, South Carolina
Conway, South Carolina
Seneca, South Carolina
Gilmer, Texas
Houston, Texas
Chewelah, Washington
Kalama, Washington
Spokane, Washington
Muscoda, Wisconsin

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