Growing Ageratum Flower: How To Plant Ageratum

By: Becca Badgett, Co-author of How to Grow an EMERGENCY Garden

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.

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These small plants do best when the seeds are sown directly outdoors, but you can always start them indoors as well. Most greenhouses also sell these plants already started if you simply cannot wait for your seeds to sprout. Ageratum is an annual plant, so you’ll need to plant new seeds every year.

Ageratum will grow in an area that is often shaded, but the plants don’t get quite as large. These little plants are native to South and Central America, so they really like the sunshine.

Ageratum, Floss Flower, Flossflower 'Blue Horizon'

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


Water Requirements:

Average Water Needs Water regularly do not overwater

Sun Exposure:


Foliage Color:




Where to Grow:


Bloom Color:

Bloom Characteristics:

This plant is attractive to bees, butterflies and/or birds

Bloom Size:

Bloom Time:

Other details:

Soil pH requirements:

Patent Information:

Propagation Methods:

From seed sow indoors before last frost

From seed direct sow after last frost

Seed Collecting:

N/A: plant does not set seed, flowers are sterile, or plants will not come true from seed


This plant is said to grow outdoors in the following regions:

Saint Francisville, Louisiana

Ladys Island, South Carolina

Gardeners' Notes:

On Jul 5, 2004, NatureWalker from New York & Terrell, TX (Zone 8b) wrote:

Sunlight: full sun or part shade. Prefers warm weather. In very hot climates, prefers part shade.

Special locations: outdoor containers, xeriscapes.

Special characteristics: deer resistant, non-aggressive, non-invasive, & native to North America - Mexico

How to plant: Propagate by seed - Start seeds indoors 6 to 8 weeks before last frost, do not cover seeds, as they need light to germinate.

Germination temperature: 70 F to 75 F
Days to emergence: 5 to 10
Ease-of-care: easy.
Maintenance and care: Pinch back plants to keep rounded and bushy, deadhead to keep in flower.

Pests: Spider mites, Whitefly .

Susceptable Diseases:
Parasitic nematodes
P. read more owdery mildew
Root rot

On Jul 4, 2004, punaheledp from Kailua, HI (Zone 11) wrote:

height on seed packet says 30" and mine have grown that tall, but want to lean to ground rather than stand upright. branches will grow upright off any branch that goes over sideways. I do not find folliage attractive, tends to curl inward, maybe something wrong with them. I would call color "periwinkle" lavender/blue, the plants saving grace. The flowers look almost fluorescent in the late afternoon/early evening light. OK if something is planted in front of them to hide folliage. I will probably not buy again.

On Mar 29, 2004, SILady from Enterprise, FL (Zone 9b) wrote:

Zone 9b - This has been a no care plant for me. Blooms year round with minimal care. I love it! It spreads and stays low. Looks really good with pinks. SILady

On Jan 22, 2003, poppysue from Westbrook, ME (Zone 5a) wrote:

Something about the tall ageratums that I prefer over the short bedding types. 'Blue Horizon' is a great cultivar. It blooms all summer, makes great cut flowers, and the butterflies LOVE it. It grows 16-18 inches tall and is a wonderful garden plant. It's seeds are sterile so don't bother collecting them. buy from a reliable source.

Ageratum Plants

Ageratum plug plants, excellent as summer bedding plants and also in pots and hanging baskets


Very pleased with attractive pots and they are of good quality.


Attractive containers of perfect size for me. Replaced damaged terracotta pots from the frost. One was slightly damaged but I have planted it and don’t anticipate any problems. Brookside are aware and happy to rectify any problems but I am optimistic.


Very good value compared to other sites, nice to have a mix of colours. Arrived in perfect condition, nice healthy plants


Arrived in perfect condition and great price


Plants all look healthy and were well packaged, I look forward to a summer of flowers


This was super easy to customise and after emailing customer support, they ensured that it went out in the next days post and arrived well in time for Mother’s Day! Fantastic! Will be a repeat customer.

How to Grow: Ageratum

in Ageratum houstonianum

Bloom Period and Seasonal Color

Ageratum bloom summer to frost in colors such as blue, white, violet and pink

Mature Height x Spread

6 to 24 inches x 6 to 12 inches

Ageratum attracts butterflies, drought tolerant, deer resistant

Ageratum is a workhorse annual flower in many New England gardens. It’s a low growing, low maintenance annual that blooms all summer in sun or part shade with little care. The small mounding plants tolerate dry, infertile soil once established. Small, button-like ageratum flowers are produced in clusters on these plants. Although various shades of blue are the most common colors of ageratum, pink and white selections are now available to broaden the color scheme and allow gardeners to mix and match ageratum with a wider variety of plants. They look particularly attractive used along the front edge of a border of annual or perennial plants or in a container with taller annuals. In my garden butterflies love to alight on patches of ageratums.

Where, When and How to Plant

Ageratum are not fussy about soil conditions as long as it’s well-drained. Purchased transplants from the local garden center and set them out into the garden planted 6 inches apart in spring after all danger of frost has passed. To produce a larger quantity of ageratum for less cost, start seeds indoors 8 to 10 weeks before the last frost date in your area. Barely cover the seed with potting soil, as they need light to germinate. Plant in full sun in cooler parts of New England. Plant in part shade in warmer regions, or if grown a warm microclimate such as near a south-facing stone wall.

Keep plants well-watered and weeded once transplanted. Although they can tolerate dry conditions, young plants need moist soil to get established. Pinch back the growing tips of young plants to stimulate them to branch out and form a bushier plant. This will lead to more flowers. Deadhead the flowers to keep the blooming all summer and for a tidier appearance.

Regional Advice and Care

During hot, dry spells spider mites can attack ageratum causing them to dieback. To prevent spider mite infestations, mist the plants during dry spells with water. Spider mites don’t like humid conditions. Cut back damaged plants if you miss the infestation and they should regrow and flower again.

Companion Planting and Design

Grow ageratum in front of walkways or in flower beds. They look great planted in masses of one color. Pair ageratum with silver foliaged plants such as artemesia. Petunias and another low growing annuals look great next to ageratum. Plant contrasting colored flowers, such as rudbeckia or tall marigolds, behind ageratum to create a nice color combination.

The ‘Hawaii’ Series’ of ageratum features white, pink and blue flowered selections that only grow 6 inches tall. ‘Hawaiian Royal’ is particularly attractive for its true blue color. ‘Blue Horizon’ is a taller growing ageratum that can reach 2 feet tall. ‘Red Top’ is another tall grower that features burgundy colored flowers. ‘Southern Cross’ features bi-colored flowers on compact plants.

Species and varieties of ageratum

Since growing of ageratum is not difficult and ornamental effect is quite high, it is not surprising that it is so popular among florists. We will present you a few popular species and the most attractive varieties of ageratum:

White ageratum

reaches up to 8 inches in height, has upright stems, fragrant white flowers.

Blue ageratum Blue Mink

is a small branched bush with strong shoots of 8-10 inches in height. Fluffy inflorescences of a gentle blue hue look like a fur of a mink as they cover the bush entirely. The diameter of the inflorescence is 2-3 inches.

Mexican ageratum

or flossflower is a compact ball-like small bush that reaches 6-24 inches in height depending on the variety. Inflorescences are from 1.2 to 3 inches in diameter, consist of flowerheads formed by fluffy flowers. The varieties are:

Watch the video: Facts about Ageratum Plants

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