How to grow ageratum?

Growing Ageratum Flower: How To Plant Ageratum

Blue flowers for the garden are sometimes difficult to grow. Choices are limited and most require a full sun location. Ageratum plants, with fluffy blue flowers, add the desirable blue color to your garden, even if it is partially shaded. Caring for ageratums is simple and easy, particularly for the beginning gardener.

The ageratum flower most commonly found in the garden is a hybrid, growing in a petite and compact form. When you learn how to plant ageratum and grow it successfully, you will always have a blue flower option for the bed or border.

What is Ageratum?

For those new to flower gardening, you may be wondering, “What is ageratum and how is it cultivated?” Ageratum houstonianum, a native of Mexico, is among the most commonly planted ageratum varieties. Ageratums offer soft, round, fluffy flowers in various shades of blue, pink or white—with blue being most common.

Ageratum plants grow from seed or from small seedlings sometimes found in garden centers. More than 60 cultivars of the blue ageratum flower are available, often reaching only 6 to 8 inches (15-20 cm.) when fully grown. The wild ageratum is a taller specimen that reseeds abundantly, but most available seeds of the ageratum will be from hybrid types.

Popular varieties of the ageratum flowers offer a range of blue colors and include the following cultivars:

  • ‘Hawaii‘ – This type has blooms of a royal blue. It flowers early and is one of the most long lasting of the species.
  • ‘Blue Mink‘ – This cultivar has flowers in a powder blue color and reaches 12 inches (30 cm.) in height.
  • ‘Blue Danube‘ – A variety that reaches just 6 to 8 inches (15-20 cm.) and features blooms in a medium blue shade.

Pink and white blooming cultivars are available as well, but tend to wither early and take on a worn, brown look.

How to Plant Ageratum

Ageratum plants may be started from seed when the soil has warmed outside. Cover seeds lightly, as seeds of ageratum plants need sunlight to germinate. For an early start to blooms of the ageratum flower, start seeds indoors eight to 10 weeks before planting in the spring garden.

Caring for Ageratums

An annual and sometimes perennial flower, the ageratum flower blooms from spring until fall when receiving proper care. Caring for ageratums includes regular watering until the plant is established. Use warm water to irrigate the plant for a bounty of blue blooms.

You should also deadhead spent blooms as needed to encourage more flowers.

Growing and caring for ageratums is simple. Stick with the popular blue blooms of the ageratum, deadhead as needed and enjoy the simple blue flower in your garden this year.

Caring for Ageratum

Ageratum – While most folks plant this popular annual as a bedding plant, it works very well in a hanging basket or window box. Food for thought while the snow is still falling.
Ageratum – If you are thinking of adding some more Ageratum to your garden bed, here are two new introductions to research.
New in 2002 – Ageratum ‘Leilani Blue’ grows to a 14-16 inch height and shows large clusters of blue flowers
New in 2004 – Ageratum ‘Alto Blue’
Ageratum – Ageratum can be started from seed indoors. Start them 6 – 8 weeks before all danger of frost has passed. Don’t cover the seeds; they need light to germinate.
Ageratum – Plant Ageratum seedlings purchased at the garden center or nursery as soon as danger of frost is past and the soil is warm (when night time temperatures stay above 50 degrees). Depending on where you live this may be as early as April or as late as June. Ageratum prefers full sun but can handle part shade. The soil should be fertile, moist and well drained. Space plants 6 to 8 inches apart depending on expected height of the variety you are planting. To avoid fungal disease problems, be sure to plant Ageratum in a location with good air circulation to help prevent fungal diseases such as powdery mildew.
Container design idea from Proven Winners for spring to early summer – In a medium to large container combine two each of Ageratum ‘Artist Purple’, Licorice Plant ‘Petite Licorice’, and Petunia ‘Supertunia Priscilla.
Ageratum – Ageratums do not want a lot of fertilizer, especially if they are growing in good soil containing lots of organic material. In that case, they want only a light feeding in the spring when the seedlings are set out, about a half a tablespoon of slow-release granular fertilizer per plant. In poor soils use a bit more; one tablespoon of slow-release granular fertilizer per plant. That is all you need for the season.
Optional task – Ageratums grow best when mulched. As soon as the Ageratum seedlings are tall enough, spread a 2 or 3 inch layer of some organic material such as chopped leaves, dried grass or wood chips on the soil around the plants.
Ageratum – This plant does not like to have its soil dry out; a moisture-retaining mulch will cut down on how frequently you have to water it.
We don’t know exactly why this happens, but those pretty blue blossoms of Ageratum will usally turn up as pink on any photos that you take; go figure.
Ageratum – Unlike many flowers in the garden, Ageratum are perfectly happy to be transplanted to a new spot when they are in full blossom. Some people keep a row of Ageratums tucked away in the vegetable garden so when holes appear in the flower bed, Ageratum is standing ready to fill in with full blue color. Best to do this on a cloudy day and water the plant very well.
Optional – Cut off old flower clusters as they brown to keep the plants looking better and blooming more. If you have a lot of brown clusters, shear the plants back about one third and you will have more blossoms in about two weeks.
Ageratum – Interesting fact – The genus name, Ageratum, is derived from Greek and means ‘without age’, a reference to the long-lasting flowers.
Ageratum – Continuing to deadhead spent blossoms keeps this plant looking good right up to first frost.
Ageratum – After the first hard frost your Ageratums will have died and can be removed to the compost pile.
Ageratum – This common annual is often called Floss Flower or Blue Fleece Flower just to keep us all confused.

True blue. There are few flowers out there that can claim that title. Ageratum (pronounced AH-jer-a-tum) is one of them, though. In addition to that perfect blue, ageratums can be pink, white or purple, too. Their soft and fluffy flower heads gives this flower a whimsical character. Ageratum is also referred to as floss flower. It has been a favorite in gardens for generations.

Ageratum (Ageratum houstonianum) is a fast-growing annual in most regions, which makes it a charming fill in for flower beds and borders. It is a great annual for container gardens, too. And in U.S. Department of Agriculture zones 10 and 11, you can enjoy this flower as a perennial.

Unlike most annuals, ageratum craves heat as it is developing. Once it is mature, it will tolerate the cold more readily, but still prefers to be toasty as opposed to other cool-loving annuals that wilt with heat. Ageratums originated in Central and South America, so its inclination to temperate conditions is a distinctive part of its nature.

How to Grow and Care for Ageratum

Start your ageratum seeds indoors 6 to 8 weeks before your last frost. Once all danger of frost has passed, take your baby plants outside. Transplant them in a sunny location. Remember, this plant loves to be warm. It will develop slowly unless given plenty of rays from the sun.

If you are using your ageratum as a bedding plant, space your plants about 8 inches apart. As the transplants grow, they will fill in quickly. Taller varieties can be spaced further apart.

Ageratum isn’t very choosy about soil conditions, but it won’t do well with soggy feet. Make sure your soil drains well. And don’t let the soil dry out either. Ageratums quickly wilt if conditions are too dry. Because it prefers warmth over cold so much, some suggest watering an ageratum with warm water as opposed to cold. Especially when the plants are young, warm water seems to speed up the growth process of this plant.

If you would prefer not to start from seed, your local nursery will probably have a transplant for you. You will enjoy the blooms of your ageratum in no time when you transplant after the danger of frost has passed.

You can expect your ageratum to bloom happily from mid-summer to that first frost of fall. And it should attract the attention of hummingbirds and butterflies for you wildlife lovers out there.

Ageratum Pests and Problems

Ageratum is generally hardy when cared for properly. There are a few pests to look out for, though. The largest-sized pest for ageratum is deer. If your plant disappears overnight, a deer is probably the culprit.

Whiteflies may weaken your plant, causing the leaves to yellow. The flies can be lured away from your ageratum with an old- fashioned fly trap. Paint a post bright yellow and cover it with honey or some other sticky substance.

If you notice your ageratum leaves are severely yellowed, wilted, and dying, or if there are lesions on the stems, your plant has probably succumbed to a bacterial infection. The unhealthy plant should be removed to avoid spread of the disease to neighboring ageratums.

You may find brown spots on the leaves or mold on the stems and flowers of your ageratum. The plant will probably survive this problem through the season. However, you may try thinning your plants to allow more air flow around the plant. Sunlight will keep the leaves and flowers drier, too, which will help deter molds from further damaging your plant.

Cultivars to Consider

With as many choices as there are, your biggest problem with your ageratum may simply be choosing just one or two of these pretty varieties. Here are a couple we thought were worth mentioning.

  • ‘Tall Blaze Horizon’ is a tall version of the more traditional bedding plant. The blazing blue color is a striking contrast to reds and yellows in the garden. This is a great variety for cutting.
  • ‘Southern Cross’ is one of a few ageratum that produce two colors in the petals. Southern Cross is white in the center and fades to a soft blue around the edges.

Here are some additional resources on ageratum:

Ageratum Houstonianum – Missouri Botanical Garden

Ageratum – Cornell University

Creative Commons Flickr photo courtesy of Les Serres Fortier

Hardy Ageratum, Mist Flower

Description of hardy ageratum: These perennials are 2-foot mounds of triangular, coarsely-toothed leaves and flat-topped clusters that bloom early in the fall.

Hardy ageratum ease of care: Easy.


Growing hardy ageratum: Mist flowers prefer a good, well-drained but moist garden soil in full sun or partial shade. They like a bit of shade in places with hot summers. Plants appear late in the spring; digging them up by mistake should be avoided.

Propagating hardy ageratum: By division in early spring or by seed.

Uses for hardy ageratum: The showy blue flowers are welcome in early fall and the plants are excellent in a border or used as edging.

ageratum related species: Both Eupatorium maculatum and E. purpureum, now classified in the new genus Eutrochium, are handsome American wildflowers called joe-pye weed. E. maculatum grows to 6 feet tall and bears rounded heads of many small, thinly fringed, purple to light purple flowers on stems that are shaded or spotted purple. E. purpureum has stems that are usually green, and the flowers smell of vanilla. Both are spectacular in the back of a border. Although adaptable to average garden soil, they prefer an evenly moist spot.

Scientific name for hardy ageratum: Conoclinium coelestinum

Hardy ageraum growing zone: USDA 6

Want more gardening information? Try:



An old-fashioned favorite annual for any garden, ageratum are tough plants that can even handle a bit of shade. Not to mention, ageratum are some of the truest blue annuals you can find! Characterized by their powder-puff blooms, these plants begin to bloom in late spring and keep the show going until the first frost. These are some rugged plants that can withstand tough soil conditions and even deer! However, take caution when planning your garden, as all parts of this plant are poisonous if ingested, so site ageratum carefully.

genus name
  • Ageratum houstonianum
  • Part Sun,
  • Sun
plant type
  • Annual
  • 6 to 12 inches,
  • 1 to 3 feet
  • 6-18 inches wide, depending on variety
flower color
  • Blue,
  • Purple,
  • White,
  • Pink
foliage color
  • Blue/Green
season features
  • Spring Bloom,
  • Fall Bloom,
  • Summer Bloom
special features
  • Low Maintenance,
  • Good for Containers
  • 9,
  • 10
  • Seed

Garden Plans For Ageratum

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Flossy Flowers

Sometimes referred to as a floss flower, ageratum has playful, small blooms that look like tiny pom-poms covered with floss-like filaments. They are known as one of the best annuals for cutting. Ageratum has been grown for years, primarily because it offers a rare color in the flower world: blue. This makes the flower perfect for patriotic plantings. Ageratum can also be found in several shades of pink, purple, and white. No matter the color, all of these blooms are very popular with pollinators. Butterflies enjoy visiting these plants and drinking their sweet nectar. Ageratum “bury their dead,” which means they are so floriferous and fast growing that there is no need to deadhead spent blooms—the plant will quickly grow past it and take care of itself. How convenient!

Ageratum Care Must-Knows

Very often, you can find these tough little plants at your local garden center in multi-packs around springtime. If you’re the type that likes to DIY, you can also start these plants in your house before the first frost-free day (see our Spring Frost Garden Zone Map for more details). Generally, 4 to 6 weeks is plenty of time to establish plants before planting them out. As soon as the frost-free date has passed, plant ageratum outside in well-drained, evenly moist soil. Just don’t get too hasty, ageratum are not fans of the cold and a late frost can wipe them out.

Ageratum can also perform well in containers—simply use a well-drained potting soil, preferably with a slow release fertilizer. These plants can be heavy feeders and will benefit from the extra food. You can also feed them regularly throughout the growing season with a general-purpose fertilizer, whether they are in ground or in pots. Ageratum will usually let you know when they need more food—they are quick to sport yellow leaves when they’re hungry. Design a tall planter using ageratum.

Ageratum can be grown in full sun or part shade, but keep in mind that if you grow your plant in the shade, you might miss out on a few extra blooms and the plant habit may become a little looser. Without full sun, plants may also have more issues with foliar diseases, such as powdery mildew. Powdery mildew is most common during wet, humid weather. Luckily, this won’t kill your plants—it’s more unsightly than anything. The best course of action is to keep plants dry and to water at the base while making sure they have proper air circulation.

See more tips on how to care for your annuals.

More Varieties of Ageratum

Artist Purple Ageratum

Rich purple blooms cover these small mounding plants, and have good heat tolerance.

‘Blue Danube’ Ageratum

Ageratum ‘Blue Danube’ bears lavender-blue flowers and grows only 8 inches tall.

‘Hawaii White’ Ageratum

Ageratum ‘Hawaii White’ grows 6-8 inches tall and has white flowers.

Plant Ageratum With:

There are few gardens that don’t have at least one salvia growing in them. Whether you have sun or shade, a dry garden or lots of rainfall, there’s an annual salvia that you’ll find indispensable. All attract hummingbirds, especially the red ones, and are great picks for hot, dry sites where you want tons of color all season. Most salvias don’t like cool weather, so plant them outdoors after all danger of frost has passed.

Just as you’d expect from something called French, these marigolds are the fancy ones. French marigolds tend to be frilly and some boast a distinctive “crested eye.” They grow roughly 8–12 inches high with a chic, neat, little growth habit and elegant dark green foliage. They do best in full sun with moist, well-drained soil and will flower all summer long. They may reseed, coming back year after year in spots where they’re happy.

You’ve gotta love annual vinca—it really delivers. It will tolerate a wide variety of conditions and still keep blooming with almost unreal-looking, glossy green flowers and pretty pink, lavender, or red flowers that look like tiny parasols. Whether the summer is dry or wet, hot or cold, vinca plugs along unfazed. It makes a great container plant, or plant it in a bed or border, grouping at least eight or more together for best effect. Plant established seedlings in spring after all danger of frost has passed. Vinca withstands drought but does best with moderate moisture. Fertilize occasionally. Like impatiens, this plant tends to be “self-cleaning” and needs little deadheading.

Hardy Ageratum, Blue Mistflower

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:

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

Guysville, 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

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