How to Plant, Grow, and Care for Floss Flower

Are you looking for a quick and easy-to-grow annual flower? Floss flower is a vibrant and showy plant that will grow from seed to full bloom within a single growing season. In this article, gardening enthusiast Liessa Bowen will share tips on how to best grow this attractive garden beauty.

A close-up reveals intricate details of purple floss flowers, their delicate petals forming a clustered masterpiece. The vivid purple color contrasts distinctly with the gentle, unfocused scenery of abundant green foliage.


Also known as blue billygoat weed, this pretty bloomer is a member of the Aster family (Asteraceae). It’s become quite popular with home gardeners, and there are several attractive cultivars to choose from. Some varieties grow tall and lanky, while others stay low, mounded, and clumping. There is also variation in flower colors.

They are typically a pale purplish-blue color but may also appear white, pink, or deeper blue. The clustered flowers are small, dense, and fluffy-looking.

They attract butterflies and make good, long-lasting cut flowers. The plants have stiff, upright stems with simple, opposite, slightly serrated leaves. 

These plants bloom from summer into fall. In ideal conditions, they may bloom throughout the summer and until the first frost, after which the entire plant will die. Plants are easy to grow but tend to become weedy as they readily self-seed. They’re not too picky about environmental conditions.

These annuals are great for growing in containers, window boxes, or a low-maintenance seasonal patio garden. Are you looking for something to help create a sunny butterfly garden? Perhaps you need bedding plants to become an attractive border or summer garden. Try growing them in any sunny location with moist soil.

Whether you’re just looking for ideas or ready to grow your own floss flowers, let’s now dig in and learn more about the details of this beautiful flowering plant.

Plant Overview

Purple floss flowers in full bloom, their delicate petals forming dense clusters that catch the sunlight. Adjacent to the purple floss flowers stand white blossoms with an ethereal quality, their translucent petals allowing a subtle interplay of light.
Plant Type Annual
Family Asteraceae
Genus Ageratum
Species houstonianum
Native Area Mexico
USDA Hardiness Zone 2 to 11
Sun Exposure Full sun to partial shade
Soil Type Average, Well-drained
Water Medium
Plant Spacing 6 to 12 inches
Suggested Uses Pollinator garden, Containers, Cutting garden
Plant With Marigold, Cosmos, Bachelor’s Buttons, Zinnia, Snapdragon
Bloom Season SummerFall
Flower Color Bluish-purple
Attracts Butterflies
Problems Weedy, Powdery mildew, May require staking
Resistant To Deer, Rabbits
Height 1 to 3 feet

Plant History

A cluster of purple floss flowers resembling plush pincushion mounds, adds a burst of color to the scene. Beneath these vibrant blooms, expansive green leaves create a lush contrast, forming a captivating botanical display.
This Mexican and Central American native grows in varied conditions.

Floss flower is native to Mexico and Central America. It grows along roadsides, fields, powerlines, disturbed areas, and open woodlands. It thrives best in rich, moist soil with full sun to partial shade.

In its native habitat, it’s a perennial wildflower, but in most other areas with cooler climates, it is grown as an annual. Because it is quick and easy to grow, it has become a popular bedding plant commonly sold at garden centers.

This plant is versatile. Low-growing clumping varieties stay under one foot tall and are helpful for edges or containers. Taller varieties can reach 2.5 to 3 feet tall and can be used in butterfly and cottage gardens.


A vibrant display of blue floss flowers in full bloom. Their delicate petals unfurling like azure stars against the backdrop of lush green leaves, creating a captivating contrast of colors in the garden.
This plant blooms from summer to fall, with potential blooming challenges in hot climates.

These plants bloom reliably from summer into fall. However, in particularly hot climates, plants may not bloom all the way up to the first frost.

Remove the dead or dying vegetation from your garden if the plants die back in mid to late summer due to extreme temperatures or prolonged drought. 

Fortunately, floss flowers are not bothered by deer or rabbits. They are mostly pest-free but occasionally have powdery mildew problems, particularly in moist, humid conditions. If insect pests are in the area, you may see them, but they typically prefer other plants and should be fairly easy to control.


As an annual plant, this wildflower is easily grown from seed. The seeds are tiny and difficult to work with, but they will grow readily if started indoors or out.

You can collect seeds from mature plants or buy them in packets. If you don’t want to start new plants from seed, they are often available as bedding plants at nurseries and garden centers.

Seeds that you self-collect from hybrid plants may not produce true-to-type and mirror their parent plant, so if you collected seeds from a pink cultivar, you may find that these offspring revert to purplish-blue flower colors.


A hand holds small brown seeds, showcasing their natural texture and color. The background is a mesmerizing blur of even more seeds, hinting at the abundant possibilities within nature's grasp.
Once the seeds sprout, maintain moist soil and provide ample sunlight to ensure robust growth.

Starting seeds indoors: Plan to start your seeds six to eight weeks before the last spring frost. Sow the seeds in clean, moist soil and water them thoroughly.

These seeds need both light and moisture to germinate. Because they are so tiny, they will not need to be planted below the soil surface. They will naturally settle into a moist crevice.

Keep the soil moist but not wet or soggy. Seeds germinate best in warm temperatures, aiming for around 75°F. Use a heat mat under the seeds to help keep them warm. Seeds germinate in 7 to 10 days.

Starting seeds outdoors: Direct sow the seeds outdoors after the last spring frost. Sprinkle them on the soil surface, rather than burying them, and water them in. Keep the soil moist until they germinate. They may take longer than seven to ten days to germinate outdoors, especially in cooler weather, because warm temperatures trigger germination.

After seeds sprout: Keep the seedlings moist but not wet. Be sure they get plenty of bright sunlight to keep them growing robust and compact.

Insufficient light will cause seedlings to grow long and leggy, and they will lean towards the light source and risk falling. Thin seedlings to one plant every 6 inches for more compact varieties or one plant every 10 to 12 inches for taller varieties.


Flourishing in a bed of earthy brown soil, purple floss flowers showcase their resilience and beauty. The clusters stand tall, a testament to nature's artistry, with their foliage adding a touch of green to the picturesque scene.
Select robust young bedding plants with fresh and firm leaves.

If you purchase young bedding plants, look for a healthy specimen. Leaves should appear fresh and firm with no signs of holes, spotting, yellowing, or curled edges.

Avoid any plants that look weak, soft, limp, or insect-infested. Young plants are commonly sold in the springtime alongside other typical spring and summer bedding plants.

When your seedlings are several inches tall, they can be transplanted outside. Seedlings grown indoors should be hardened off for a week before transplanting.

During the daytime, move them outside to a somewhat protected location to help them get adjusted to outdoor conditions. Bring them back in at night or during the night. Each day, gradually increase the time they spend outside.


Skilled gardener's hands firmly grasp a green trowel, excavating the soil within a wooden plant bed. In the eager grip of the other hand, a promising seedling yearns for its new home, poised to join the bed's thriving community.
Transplant seedlings by digging a hole, placing the plant, and watering well.

Transplant seedlings outside in the springtime after all danger of frost has passed. Using a transplanter, dig a hole slightly larger than the root mass of the potted plant. Then, gently remove the plant from its pot and transfer it into the hole. Fill in the gap around the root mass with fresh soil. 

Time transplanting for a cool, overcast day. After planting, water any transplants well to help them settle into their new home.

Keep the soil moist for at least two weeks after transplanting. Once they start to grow a bit, taller plants may need staking to maintain an upright position.

How to Grow


A profusion of purple floss flowers in full bloom, proudly extending above their long and graceful stems. The surrounding green leaves provide a beautiful contrast to the rich purple blossoms.
This wildflower thrives in 6 to 8 hours of bright light.

These flowers do best in full sun to partial shade. In cooler climates, they generally prefer full sun, while in the warmest climates, they may prefer some afternoon shade. Generally, six to eight hours of bright light will be best.


Purple floss flowers, delicate and vibrant, bask in the warm sunlight, showcasing their rich hue in a garden. Beneath the blossoms, their lush green leaves flourish in the nourishing embrace of the rich, dark soil.
Properly water your plants to maintain moisture and prevent wilting during dry spells.

Keep the soil moist for your floss flower plants. Once established, they are relatively drought-tolerant but may wilt if left thirsty for too long.

During extended periods of dry weather, you will want to add some supplemental watering to keep these plants happy.


Flourishing gracefully in the rich, dark soil, the purple floss flowers stand out with their captivating beauty. Their lush foliage adds depth to the scene, creating a harmonious balance of colors and textures that delights the senses.
This plant favors moisture and rich soil.

The soil should be generally moist and well-drained. Floss flower plants prefer soil rich in organic matter but are not too picky about soil quality. Average-quality soil will grow healthy plants, while nutrient-rich soil will grow more robust. 

Climate and Temperature 

Bunches of tall purple floss flowers, held by sturdy green stems and leaves, create a vibrant display. Among the majestic purple floss flowers, cheerful yellow flowers add a sunny contrast.
This frost-sensitive plant requires protection from cold and extra care in hot, dry climates.

These plants can be grown as annuals in USDA plant hardiness zones 2 through 11. In zones 10 and 11, it may grow as a short-lived perennial.

It is sensitive to frost and will die if exposed to temperatures below freezing. It will appreciate some shade and extra watering in very hot and dry climates. 


A hand with fingers outstretched reaches towards a mound of rich, brown soil, ready for planting. The soil appears loose and crumbly, hinting at its fertility and potential for nurturing growth.
Floss flower thrives in nutrient-rich soil without requiring extra fertilizer.

As a quick-growing annual, this species doesn’t require fertilizer during its short lifetime. However, you’ll have the nicest-looking plants if you grow them in nutrient-rich soil.

A decent-quality garden soil should provide ample nutrients. If you are growing your plants in particularly nutrient-poor soil, add some general all-purpose flower-garden fertilizer early in the season to boost nutrients.


A close-up of a group of vibrant purple floss flowers, highlighting their delicate fluffiness and intricate textures. The backdrop features lush green leaves and occasional blossoms, creating a rich natural tapestry.
Stake tall varieties and remove spent flower heads.

While this plant is easy to grow, it requires some maintenance to perform its best. If your taller variety is leaning over, stake it to keep it upright. To prevent unwanted spread, remove spent flowerheads before they mature into seedheads

Garden Design

Purple floss flowers with their delicate petals forming a striking contrast against the surrounding greenery. Lush leaves frame the flowers, creating a rich tapestry of colors and textures in this garden scene.
Enrich the garden’s charm with clusters of lavender blooms.

Incorporating these pretty blooms into your garden design should be fairly simple. For smaller varieties, you should plan at least 6 inches between plants, and for larger varieties, allow 10 to 12 inches of space between plants.

Plant several together in a cluster to maximize their attractive flowering effect. Try an assortment of different varieties for a colorful display.


‘Leilani Blue’

A profusion of Leilani blue floss flowers, surrounded by lush green leaves, creates a vibrant scene. Each bloom showcases soft, fluffy blue petals, adding a touch of elegance and serenity to the arrangement.
‘Leilani Blue’ flowers are vibrant blue that grow 14-16 inches tall.

The vibrant blue flowers of ‘Leilani Blue’ offer a stunning floral display. This variety grows 14 to 16 inches tall and makes excellent cut flowers.

‘Blue Horizon

Tiny blue horizon flowers rest upon lush, furry green stems, complemented by broad glossy leaves. In the backdrop, a fusion of vibrant green and rich deep purple leaves creates a captivating, blurred tapestry of colors.
‘Blue Horizon’ plant grows about 3 feet tall with attractive flowers.

‘Blue Horizon’ grows into a fairly tall plant, reaching almost 3 feet. It has very fluffy-looking flowers that attract pollinators and make stunning cut flowers.  

‘Red Bouquet’

A bountiful arrangement of vibrant red bouquet floss flowers stands out against a backdrop of lush greenery. These stunning flowers captivate with their elegant pink hues, creating a striking and colorful display.
‘Red Bouquet’ is a striking pink variety.

Here is a dazzling pink variety. ‘Red Bouquet’ grows 12 to 24 inches tall and would make a beautiful cut flower. Its rich pink blossoms will stand out in any garden setting, complimenting other flower colors well.

‘Blue Mink’

Delicate blue mink flowers, displaying a purple hue, contrast beautifully with their vibrant green leaves. The plush texture of the blue mink petals adds a touch of softness, while the serrated edges of the leaves provide an intriguing visual texture.
‘Blue Mink’ is a compact variety with mini pom-pom flowers.

‘Blue Mink’ is a more compact variety, generally staying less than 12 inches tall. Its deep purple-blue flowers look like mini pom-poms. The flower heads seem to float above the leaves on taller stems, making them a good candidate for cut flowers. 

‘Dondo White’

Dondo white flowers stand out, their delicate petals stark against a soft, blurred background of lush green leaves. These flowers, known for their fluffy blooms, exhibit a pristine elegance that captivates the eye.
‘Dondo White’ grows up to 24 inches.

If you’re looking for a white variety, ‘Dondo White’ will do the trick. Dondo White grows up to 24 inches tall and would make a beautiful complement to any of the more colorful varieties.

Wildlife Value

A display of purple floss flowers in full bloom, creating a sea of rich color and delicate petals. The background is a soft blur, highlighting the lush foliage and adding depth to the scene of blooming purple floss flowers.
They withstand deer and rabbit pressure.

Though not native to North America, the flowers still attract butterflies and pollinators. These whimsical blooms are a good option if you’re looking for a quick filler plant for a butterfly or butterfly-friendly container garden.  

Pests and Diseases

Floss flower is generally resistant to many common pests and diseases and should be mostly trouble-free for the home gardener. You may occasionally see an insect outbreak, but most insects prefer other host plants.

Root Rot 

A close-up reveals brown roots intertwined against a soft, blurred backdrop of lush greenery. Unfortunately, the roots display signs of root rot, tarnishing the otherwise vibrant scene with the effects of disease.
Excessively wet soil causes root rot, leading to yellow leaves, rotten stems, and plant death.

If the soil stays wet and the roots are saturated, this species may develop root rot, causing the entire plant to die. You will first notice yellowing leaves, followed by soft, rotten stems. A floss flower plant with root rot is unlikely to survive even if moved to better-draining soil due to its relatively small root system, so consider removing the plant with root rot from your garden and avoid saturated soils in the future.

Powdery Mildew 

A close-up of a green leaf covered in a delicate layer of powdery mildew. This leaf's lush color contrasts with the powdery substance, a reminder of nature's intricate battles between life and the elements.
Powdery mildew can be identified by its white spots on leaves.

Powdery mildew can occasionally be problematic, especially in moist, humid environments. Powdery mildew can be detected by grayish or white spots or coating on the leaves.

You can help prevent powdery mildew by allowing ample space between plants to encourage good air circulation. Also, avoid any supplemental watering from overhead, directing the water toward the soil and the roots where it’s most needed.


A close-up reveals a multitude of small, vibrant green aphids tightly grouped on a fresh, verdant stem, showcasing nature's intricate details. The aphids' delicate bodies feature pearlescent reflections under the light.
Aphids are small insects that feed on plants, leaving behind sticky honeydew.

You may occasionally see aphids on your plants. Aphids are small, soft-bodied insects with greenish or pinkish bodies that feed along the stems and leaves.

You may see the insects themselves or the sticky, sappy honeydew secretions they leave behind. Hit heavy infestations with a strong, direct spray from the hose, and focus your efforts on attracting their natural enemies to the garden.

Frequently Asked Questions

Will floss flowers become invasive and take over my garden?

This plant is unlikely to become invasive. It can, however, become weedy and spread beyond its original boundaries, particularly in warmer climates. If you are concerned about unwanted spreading, remove spent flower heads to prevent them from going to seed.

How long does it take for a floss flower to grow from seed to flower?

If you start them from seed, you can expect them to take at least two months to reach flowering maturity. Many people prefer to start seeds indoors to get a jump start on the growing season, but even if you sow seeds directly outdoors in the springtime, they will still be flowering by mid to late summer.

Do I need to prune my floss flower plants?

No pruning is necessary with these plants. If you experience any problems with pests or diseases, remove the diseased sections to prevent infections of nearby healthy parts of the plant. The only minor pruning to do is simply deadheading the spent flowers to improve the plant’s appearance, encourage new growth and flowering, and keep them from going to seed.

Final Thoughts

Anytime you are looking for an attractive annual flower to brighten your garden, consider adding floss flowers. You can grow them in containers, raised beds, window boxes, borders, edges, flower gardens, and butterfly gardens. They provide quick and easy color for your home landscape and make beautiful cut flowers. Remember that wildflower prefers plenty of bright sunlight with moist, well-drained soil. Try some different cultivars for variety, and use them in mixed plantings for a stunning summer display!

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